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Author Topic: Sentinel ACIV  (Read 32047 times)

Offline Abraham Gubler

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« on: November 26, 2009, 07:53:36 pm »
British tanks had the following turret ring diameters:
Cromwell - 60 in (1524 mm)
Comet - 64 in (1626 mm)
Challenger - 70 in (1778 mm)
Sherman* - 69 in (1753 mm)

And the Australian Sentinel ACIV tank with 17 pounder had a turret ring of 70” (1,778mm).
« Last Edit: December 04, 2009, 05:26:21 am by Jemiba »
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Offline JohnR

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« Reply #1 on: November 27, 2009, 05:33:37 am »
I have always been intrigued by the Sentinel, an amazing achievement when considering it was a design built from scratch in terms of design and engineering capability.  That they achieved a design that could take the 17pdr ahead of the UK is also amazing.

I have often wondered how it would have performed against German tanks?
« Last Edit: December 04, 2009, 05:26:35 am by Jemiba »

Offline Petrus

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« Reply #2 on: November 27, 2009, 06:19:50 am »
And the Australian Sentinel ACIV tank with 17 pounder had a turret ring of 70” (1,778mm).

I've read somewhere that when the Challenger was designed it was thought that minimum turret ring diameter allowing to mount the 17-pdr was 66in (1676mm).



Piotr
« Last Edit: December 04, 2009, 05:26:53 am by Jemiba »

Offline Abraham Gubler

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« Reply #3 on: November 27, 2009, 03:22:14 pm »
I have always been intrigued by the Sentinel, an amazing achievement when considering it was a design built from scratch in terms of design and engineering capability.  That they achieved a design that could take the 17pdr ahead of the UK is also amazing.

And in 1943 apart from preparing a 17 pounder armed version the Sentinel tank program was also running torsion bar suspension versions… So in 1944 they could have been producing something not far from the tank state of the art of the 1950s.

The key reason Australia was able to produce in the Sentinel a tank superior to what the British and the Americans were producing at the same time is the clean slate approach. Without the impost of established industry and their factories and established tank experts and their opinions the Sentinel emerged as the best that could be built based on war experience. While there were lots of critical shortages this often lead to some innovative solutions that may have been superior to the state of art. For example instead of a single high power engine clover-leafing together three engines enabling clutching in and out of engines as per power need and resultant lower fuel consumption, wear and tear (COPAP).

Also the start up Australian tank industry wasn’t as bad off in relation to workforce as people tend to believe. There were a few key engineers with lots of experience including a couple sent to the UK to learn tank building and a refugee French suspension expert. Also the rest of the workforce were all experienced train builders working in their workshops.

Back to turret rings. The original Sentinel Mks 1-3 had a 54” (1,370mm) turret ring. They were able to mount and fire the 17 pounder and even a twin 25 pounder used to simulate 17 pounder recoil before they were available. It was able to do so because turret rings are not actually a direct indicator of a turrets ability to mount and fire a gun. The turret ring just gives an indication of turret size if it has vertical walls (like most British and American tanks at the time).

The Sentinel had angled out and angled in walls so the turret volume and maximum diameter was actually larger than indicated by the turret ring. The Mk 4 Sentinel had a larger turret ring to improve this volume further and make it easier to elevate the 17 pounder and move ammunition from the hull to the turret (also to lengthen the tank to increase track surface area to keep ground pressure stable as the weight increased). Also the Sentinel program was producing far superior recoil absorbing mounts at the time. It was actually the Australian gun mount that was used for the Sherman Firefly to fire the 17 pounder.

I have often wondered how it would have performed against German tanks?

The Sentinel Mk 4 had a 17 pounder with 60 rounds of ammunition and 110 volt electrical turret traverse, a maximum speed of 56kph and a gross weight of only 32 tonnes. Glacis armour was only 51mm but highly oblique so presenting an actual thickness of 120mm to the horizontal. Turret walls was sub-standard at only 50-65mm but provided all round, but angled or layered to provide between 71-100mm to the horizontal. 510 Mk 4s were ordered for production (including 110 with interchangeable 25 pounder gun) to follow from 200 Mk 3s with 25 pounder. Only one tank of this full rate production following the initial batch of 65 Mk1s (2 pounder gun) was built.

More data at:

http://www.mheaust.com.au/Aust/Research/Sentinel/sentinelmk.htm
« Last Edit: December 04, 2009, 05:27:09 am by Jemiba »
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Offline JohnR

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« Reply #4 on: November 27, 2009, 04:35:58 pm »
Interesting read, thank you.

Regards.
« Last Edit: December 04, 2009, 05:27:22 am by Jemiba »

Offline Kadija_Man

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« Reply #5 on: November 27, 2009, 08:40:43 pm »
One of the developers of the Firefly was inspired by the AC3 "Thunderbolt" (with twin 25 Pdrs), after reading of its ability to withstand the recoil of the two guns fired simultaneously.  

Australia's real problem with the Sentinel was that it was completely inappropriate for the needs of the defence of Australia at that time.  The Army wanted to fight in Europe, not the Pacific and so decided they needed a tank capable of defeating the best the Germans had produced, rather than one which was needed to defeat the best the Japanese had produced.  In the end though, it was economics which saw it off.  A clear choice between producing aircraft and small ships or tanks and when it was obvious that tanks were available more cheaply and easier from overseas, the die was cast and the Sentinel was quietly put out to pasture.  Its only use in propaganda campaigns and a movie ("Rats of Tobruk" where the only unit actually equipped with them used them to portray German Panzers).  As technically superior as they might have been or become, the M3 Grant/Lee was the better vehicle on the grounds of economics.

I heartily recommend A.T. Ross' "Armed and Ready: Australian Defence Preparedness 1900-1945" for an excellent discussion about the problems of the Sentinel programme.
« Last Edit: December 04, 2009, 05:27:41 am by Jemiba »

Offline Abraham Gubler

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« Reply #6 on: November 27, 2009, 10:33:55 pm »
One of the developers of the Firefly was inspired by the AC3 "Thunderbolt" (with twin 25 Pdrs), after reading of its ability to withstand the recoil of the two guns fired simultaneously.  

They weren’t just inspired they obtained examples of the overhead short recoil system which was used as the technology base for the Firefly mounting.

Australia's real problem with the Sentinel was that it was completely inappropriate for the needs of the defence of Australia at that time.  The Army wanted to fight in Europe, not the Pacific and so decided they needed a tank capable of defeating the best the Germans had produced, rather than one which was needed to defeat the best the Japanese had produced.

That is totally wrong. The original requirement was to equip an armoured division to fight in North Africa as the British could not meet additional Australian demand for tanks. When the Japanese attacked the Australian armoured divisions (1-3) were re-rolled from training for North Africa for preparing to resist a Japanese invasion of Australia. The plan was to meet them with tanks and destroy them. The requirement for this role was something built in Australia because if the Japanese were invading then it’s unlikely that convoys of American and British equipment would have made it through and the Mk 1 Sentinel was all Australian.

After the victories of 1942 it was clear the Japanese couldn’t invade so the armoured divisions were disbanded and the domestic tank program halted. If Sentinel tank production had continued with the Mk 3 it would have been far better suited for fighting in the Pacific than the Stuart and Matilda tanks the Australian Army used.

In the end though, it was economics which saw it off.  A clear choice between producing aircraft and small ships or tanks and when it was obvious that tanks were available more cheaply and easier from overseas, the die was cast and the Sentinel was quietly put out to pasture.

Again more “common knowledge” which is equally wrong as the last statement. Sentinel production couldn’t compete with importing tanks from America. It was never an issue of building aircraft or ships or tanks. But rather domestic production competing with imports. As Australian labour was very short it was redirected from production of tanks and aircraft as these supply sources improved from our allies. n 1943 Australia cancelled production of the domestic Sentinel, the CA-15 fighter and the Woomera bomber. Much of the Sentinel industry capability went into supporting the huge fleets of landing craft that were flooding into the Pacific for use against Japan. Aircraft production continued at a reduced rate on other types but more so to retain industry capacity for post war use.
« Last Edit: December 04, 2009, 05:27:53 am by Jemiba »
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Offline Kadija_Man

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« Reply #7 on: November 28, 2009, 05:50:40 pm »
One of the developers of the Firefly was inspired by the AC3 "Thunderbolt" (with twin 25 Pdrs), after reading of its ability to withstand the recoil of the two guns fired simultaneously.  

They weren’t just inspired they obtained examples of the overhead short recoil system which was used as the technology base for the Firefly mounting.

They did not request the examples until after they had read about the "Thunderbolt's" ability to absorb the recoil of its twin 25 Pdrs on such a comparatively small turret ring diameter, Abraham.  Hence the use of the word "inspired".

Quote
Australia's real problem with the Sentinel was that it was completely inappropriate for the needs of the defence of Australia at that time.  The Army wanted to fight in Europe, not the Pacific and so decided they needed a tank capable of defeating the best the Germans had produced, rather than one which was needed to defeat the best the Japanese had produced.

That is totally wrong. The original requirement was to equip an armoured division to fight in North Africa as the British could not meet additional Australian demand for tanks. When the Japanese attacked the Australian armoured divisions (1-3) were re-rolled from training for North Africa for preparing to resist a Japanese invasion of Australia. The plan was to meet them with tanks and destroy them. The requirement for this role was something built in Australia because if the Japanese were invading then it’s unlikely that convoys of American and British equipment would have made it through and the Mk 1 Sentinel was all Australian.

After the victories of 1942 it was clear the Japanese couldn’t invade so the armoured divisions were disbanded and the domestic tank program halted. If Sentinel tank production had continued with the Mk 3 it would have been far better suited for fighting in the Pacific than the Stuart and Matilda tanks the Australian Army used.

Again, you miss the point, Abraham.  It was inappropriate because there was never any likelihood after December 1941 that any Australian armoured division was going to fight in North Africa.   Even if it had, taking yet another completely different type of tank to that theatre in such small numbers would have made it impossible to support the numbers required.  Finally, if the tank was intended to defend Australia against the perceived Japanese threat, then it was too heavy and heavily armoured to be easily deployable over the very poor transport system available (rather as the M1 Abrahms are today).  It would have been even worse in the SW Pacific.  The Mk. 3's only advantage over the Stuart and the Mathilda would have been its armament.  The Stuart was not used after the "Battle of the Beachheads" because of its light armour but the 'tilly was an excellent balance of protection, mobility and armament and so was the preferred vehicle in the SW Pacific (even after the M3 and M4 Mediums became available).  

Now, you may wish to live in some fantasy land where those factors were ignored but in real life they were the determinants, along with the real killer - the ease and cheapness of imported AFVs in the form of the M3 medium series,  which ensured that Sentinel programme was dismantled.

Quote
In the end though, it was economics which saw it off.  A clear choice between producing aircraft and small ships or tanks and when it was obvious that tanks were available more cheaply and easier from overseas, the die was cast and the Sentinel was quietly put out to pasture.

Again more “common knowledge” which is equally wrong as the last statement. Sentinel production couldn’t compete with importing tanks from America. It was never an issue of building aircraft or ships or tanks. But rather domestic production competing with imports. As Australian labour was very short it was redirected from production of tanks and aircraft as these supply sources improved from our allies. n 1943 Australia cancelled production of the domestic Sentinel, the CA-15 fighter and the Woomera bomber. Much of the Sentinel industry capability went into supporting the huge fleets of landing craft that were flooding into the Pacific for use against Japan. Aircraft production continued at a reduced rate on other types but more so to retain industry capacity for post war use.

Abraham, Australia suffered from a lack of manpower.  Indeed, it had over-committed itself to putting men into uniform to the point that units were demobilised in late 1944-early 1945 in order to keep the civilian economy working.   I wonder if you actually read what I said.  "Light ships", the last time I checked, included landing craft and indeed they made up a large bulk of what our shipyards produced.  It was a choice of either the light ships (Destroyers, Corvettes, Landing Craft, etc) and aircraft (Beauforts, Mosquitos, Beaufighters, Boomerangs, Wirraways, etc) or tanks instead of one of the preceding two.   The government decided it could import the tanks so discontinued the Sentinel programme.   Now Abraham, I named my source.  Can you please name your source(s) for these claims?
« Last Edit: December 04, 2009, 05:28:10 am by Jemiba »

Offline Abraham Gubler

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« Reply #8 on: November 28, 2009, 09:54:04 pm »
Ahh another wonderful ego + ignorance battle for all to behold…

 
They did not request the examples until after they had read about the "Thunderbolt's" ability to absorb the recoil of its twin 25 Pdrs on such a comparatively small turret ring diameter, Abraham.  Hence the use of the word "inspired".

So you agree that they weren’t just inspired they based their solution on the Australian technology. To leave it at just “inspired” would mean that the British heard about this great recoil absorbing system and then went off and did their own thing. Inspiration happens daily, building a new short recoil system enabling a high power gun to be fitted to a turret that previously only held a medium power gun happens very rarely, the difference is considerable. So give credit where credit is due and don’t just leave the role of Australian technology in the Sherman Firefly program as “inspiration” rather than the actual starting point. That is as misleading as not acknowledging the downunder involvement at all.

Again, you miss the point, Abraham.  It was inappropriate because there was never any likelihood after December 1941 that any Australian armoured division was going to fight in North Africa.   Even if it had, taking yet another completely different type of tank to that theatre in such small numbers would have made it impossible to support the numbers required.  Finally, if the tank was intended to defend Australia against the perceived Japanese threat, then it was too heavy and heavily armoured to be easily deployable over the very poor transport system available (rather as the M1 Abrahms are today).  It would have been even worse in the SW Pacific.  The Mk. 3's only advantage over the Stuart and the Mathilda would have been its armament.  The Stuart was not used after the "Battle of the Beachheads" because of its light armour but the 'tilly was an excellent balance of protection, mobility and armament and so was the preferred vehicle in the SW Pacific (even after the M3 and M4 Mediums became available).  

Ahh a subscriber to the gross weight theory of tank warfare… clear indication of someone who knows something more than a person on the street but not enough to be credible.

So what you are suggesting is in December 1941 the Sentinel tank program should have been abandoned and a new program started from scratch to build a lighter tank because clearly – as everyone knows – the Japanese only had light armour and anything over some undefined weight limit can’t be used anywhere near the Pacific Ocean? What a total load of crap.

The Sentinel was the best tank to defend Australia against Japanese invasion and it was the best tank to take the Pacific Islands back from Japan. And one doesn’t even need to assess its capability or mobility because it was the only thing domestically available within the timeframe. A tank that weighs 32 tonnes is better than a tank that weighs 0 tonnes.

As to the claim of poor transport systems this pretty much effects anything over a man portable load in the same way. Since the Sentinel only weighed 7 tonnes more than the Matilda (32 vs 25 tonnes) this would have made little difference. In the Australian defence scenario it’s a no argument.

Now, you may wish to live in some fantasy land where those factors were ignored but in real life they were the determinants, along with the real killer - the ease and cheapness of imported AFVs in the form of the M3 medium series,  which ensured that Sentinel programme was dismantled.

The Sentinel was more than suitable for the Australian Army mission in the war against Japan. It was far more suitable than any alternative both real and imagined. Of course it couldn’t compete economically with the imports but it was never cancelled because it was considered unsuitable. To try and generate this argument based on a fanciful concept of lead time required to build a tank, a lack of appreciation of the tanks role in defence of Australia warfare (not tank vs tank but tank vs infantry), attribution of awesome insight into the nature of all Japanese tank armour to the Australian Army and a magical belief that a certain gross weight makes a tank immobile; is an insult to the kind of appreciation of military technology that is the norm here at secretprojects.co.uk.

  I wonder if you actually read what I said.  "Light ships", the last time I checked, included landing craft and indeed they made up a large bulk of what our shipyards produced.  It was a choice of either the light ships (Destroyers, Corvettes, Landing Craft, etc) and aircraft (Beauforts, Mosquitos, Beaufighters, Boomerangs, Wirraways, etc) or tanks instead of one of the preceding two.   The government decided it could import the tanks so discontinued the Sentinel programme.  


No our shipyards did not produce many light ships, destroyers, corvettes, etc after 1943. Nor was the aircraft industry manufacturing those aircraft that you claim. The Beaufort and Boomerang programs were effectively over, Wirraway kept on for make work and Mosquito only starting up with most of it actually been done in the UK.

The workforce wasn’t needed for building ships or aircraft but supporting those that had been built, imported and operated near Australia by our allies. So industry like the Sentinel program converted to providing spare parts, repair and other supporting services to the huge fleets of landing craft and so on. It wasn’t as glamorous as building some of the best tanks or fighters in the world but it won the war which was the important thing.

 
  Now Abraham, I named my source.  Can you please name your source(s) for these claims?

I sincerely doubt you’ve actually understood anything in Ross’s “Armed and Ready” by the statements you’ve made above. But please feel free to make various references to other books that don’t support your arguments.
« Last Edit: December 04, 2009, 05:28:23 am by Jemiba »
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Offline Kadija_Man

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« Reply #9 on: November 28, 2009, 10:55:45 pm »
Ahh another wonderful ego + ignorance battle for all to behold…

At which point it would be better to leave it there, Abraham.  I see little further point in battling with both your ignorance and ego.   It is obvious you have only a superficial understanding and no experience of these topics.
« Last Edit: December 04, 2009, 05:28:41 am by Jemiba »

Offline Abraham Gubler

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« Reply #10 on: November 28, 2009, 11:48:40 pm »
At which point it would be better to leave it there, Abraham.  I see little further point in battling with both your ignorance and ego.   It is obvious you have only a superficial understanding and no experience of these topics.

Nice to see that even when you’re just typing insults you don’t want to deviate from your steady course of never letting a fact get in the way of a good opinion.
« Last Edit: December 04, 2009, 05:29:04 am by Jemiba »
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Offline Abraham Gubler

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« Reply #11 on: November 29, 2009, 12:03:07 am »
If Rickshaw’s attempts to rewrite Australian defence history is behind us perhaps we can return to the original question…

The design for Sentinel Mk 4 armed with an interchangeable 17 or 25 pounder had a turret ring of 70” but none of these tanks were actually built.

And the Australian Sentinel ACIV tank with 17 pounder had a turret ring of 70” (1,778mm).

The Australian War Memorial picture I attached in this original Sentinel turret ring post was not of a Mk IV but rather the E1. The E1 was a highly modified Mk 1 Sentinel that was used for trial mounting the 17 pounder. It was the famous tank with the turret with two 25 pounders mounted to simulate 17 pounder recoil (they actually generated 120% of the recoil).

The whole point of this post is the E1 had a 64” (1,624mm) turret ring. So it would be feasible to mount a regular 17 pounder on a Comet tank chassis with a new turret. But loading would be limited to a horizontal or depressed gun elevation.

For fans of the Sentinel here is what the Mk 3 or 4’s new hull front looks like with the removal of the hull gunner.
« Last Edit: December 04, 2009, 05:29:16 am by Jemiba »
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Offline JohnR

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« Reply #12 on: December 01, 2009, 03:34:44 pm »
Thats a big aesthetic improvement over the rather odd looking bow gunners, and I would imagine a considerable balistic improvement.

Regards.
« Last Edit: December 04, 2009, 05:29:30 am by Jemiba »

Offline Abraham Gubler

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« Reply #13 on: December 04, 2009, 04:13:55 am »
After another look at “Armed and Ready” Rickshaw is right that Andrew Ross does criticize the Sentinel as being “unsuited” for use against the Japanese. But he counters and qualifies his own argument a few times and his reasoning is very unsound (having spent quite a few years a decade or so ago serving on some committees with Dr Ross I don’t find this a surprise at all! Great guy but).

He points out that the original staff requirement for an Australian built tank in ‘40 was for something around 10 tons with minimal armour and able to counter Japanese light tanks. This was changed quite quickly to a medium tank able to fight German tanks after the Blitzkrieg in France. While Ross criticizes this decision it is heavily informed by hindsight. In 1940 Australia was at war with Germany and while the Japanese were considered a major threat all the planning to fight them was done so in the context of the Singapore and Bataan fortresses. The idea that the Japanese could defeat and advance past the UK and USA forces into SE Asia and the SW Pacific was considered ludicrous before they did it. In this context the land fight against Japan was seen as fighting them off from fixed positions and the need for a light anti-Japanese tank is a poor second to the medium anti-German tank.

Ross’s main criticism of the Sentinel program is that after the Japanese attack the Army kept asking for improved weapons (17 Pounders) to fight the Germans when 2 Pounders were adequate for defeating Japanese tanks. While this argument is on more solid ground it doesn’t take into account that the Australian Government made a commitment to retain a division in the European theatre until the end of the war and said division would require tanks (just like the equivalent NZ division). It was only after the loss of an Australian division in Singapore and Java thanks to poor British command that the European division was recalled to Australia and the policy changed (even then it stayed until after El Alemein).

Ross agrees that the Sentinel Mk 3 with 25 pounder was the best suited tank to fighting the Pacific campaign against the Japanese. He still remains critical of its medium size but this thick armour would be crucial for its survivability and didn’t appear to be a production bottleneck for the Sentinel. The cast armour by Bradford Kendall Ltd (still casting steel today) was one of the success stories of the program and enabled rapid design evolution compared to jigged welding or bolting production.

Japanese anti-tank tactics may not have used big guns but were sufficient to require medium tanks and clear light tanks from the battlefield. Because of the close terrain their 20mm anti-tank gun was extremely lethal against light tanks and their heavy use of mines and suicide command detonated explosives required strong protection. The Sentinel with its thick castings of softer but tougher steel alloy made it very resistant to spalling from blast effects.

As to the difficulties of moving a 30 ton tank into the SW Pacific battlefield they aren’t much more difficult than moving a 10 ton tank. Once on the ground the difference is minimal (thanks to equal ground pressure) and with no such thing as local bridging this is not an obstacle. A US Army study in the mid 1960s found that 50% of South VietNam was accessible to main battle tanks (50 tons). Which is amazing considering a quarter of South VietNam is the Mekong river delta impassible to any weight bearing vehicle and another third is the central highlands a thickly forested mountain range.

PS Perhaps a moderator should split a lot of this off to a separate Sentinel thread?
« Last Edit: December 04, 2009, 05:29:44 am by Jemiba »
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Offline Abraham Gubler

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« Reply #14 on: December 04, 2009, 04:17:27 am »
Thats a big aesthetic improvement over the rather odd looking bow gunners, and I would imagine a considerable balistic improvement.

Its a very well shapped tank. The strange looking bow gunner ball in the Sentinel Mk 1 was influenced by the use of Vickers .303 MG. Since Australia didn't have BESA or 7.92mm production they had to use the Vickers with the barrel shroud.

Here are pictures of the side and rear of the Mk 3. The turret ring is actually in a depressed section surrounded by bulwarks so any shot can't hit it directly.
« Last Edit: December 04, 2009, 05:29:58 am by Jemiba »
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Offline JohnR

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Re: Sentinel ACIV
« Reply #15 on: December 04, 2009, 10:21:24 am »
I am intrigued by the picture of the rear of the tank, it appears to have a solid plate over the engine compartment.  Is this original or has it been added later, if it is original how was the engine cooled as there does not appear to be an air intakes?

Offline Abraham Gubler

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Re: Sentinel ACIV
« Reply #16 on: December 04, 2009, 02:54:47 pm »
I am intrigued by the picture of the rear of the tank, it appears to have a solid plate over the engine compartment.  Is this original or has it been added later, if it is original how was the engine cooled as there does not appear to be an air intakes?

That was the design through the various marks of the Sentinel. The air vents for cooling are located under armour lips mounted along the side of the tank between the hull wall and the storage boxes. I've defaced these pictures of a scratch built model of a Mk 1 by Michael Koudstaal to point out the intakes and exhausts. On the Mk 3/4 Sentinel the intake level with the turret were covered by an armoured housing that also protected the sides of the turret ring.
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Offline JohnR

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Re: Sentinel ACIV
« Reply #17 on: December 04, 2009, 03:59:12 pm »
Interesting, thank you.

Offline Abraham Gubler

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Re: Sentinel ACIV
« Reply #18 on: April 03, 2011, 03:48:45 pm »
The Australian Cruiser (AC, aka Sentinel though this name only applied to the AC Mk 1) tank had a unique power plant approach using multiple low power car engines to provide high power output in the absence of a single high power unit. While leading to complex transmission solutions this provided the advantage of redundancy and efficient low power running. All versions of the AC had multiple engines but with very different arrangements.

The AC1 Sentinel had three Cadillac 75 V8 engines (the famous car engine built in Australia by GM Holden) mounted in a cloverleaf with one on the centreline aft and two port and starboard amidships with shafts from each engine running forward to a transverse transfer box mounted under the turret basket (see picture AC1.png). The combined power of the engines was then shafted forward to the transmission via a single, centreline shaft with an output of 330 hp. Interestingly in the engine bay the three engines, radiators, fans and fuel tanks were all mounted on a common subframe and could be lifted in and out of the engine bay together.

The next variant the AC Mk 3 Thunderbolt (AC Mk 2 was a design study only for a very different tank) armed with the 25 Pounder (88mm) medium velocity gun kept the three engines but in a totally different arrangement. The three Cadillac 75 engines were mounted radially on a single triangular steel case (AC3_1.png) where they shared a common crankcase and integral transfer box. This radial mount was designed by French tank designer Mr Perrier who had been in Japan on loan from the French Government in 1940 before making his way to Australia. When fitted with the three engines the single unit was known as the Perrier-Cadillac 41-75 (AC3_2.png, aft view, note the alternator on the top engine). Also added to the frame was the fans and radiators enabling a very compact single unit without the need for the bulky under turret transfer case and subsequent power loss (AC3_3.png, forward view, note the single transmission shaft attachment below the fans). A single shaft ran under the turret floor forward to the transmission on the AC3 (AC3_4.png) with an output of just under 400 hp.

The AC Mk 4 armed with the 17 Pounder (76mm) high velocity gun was to have kept the Perrier-Cadillac 41-75 in at least the initial versions. A new engine was under development combining four Gipsy Major I4 engines (built in Australia by GM Holden for the de Havilland Australia Tiger Moth production line). This arrangement would have the potential for around 500 hp output using a very simple and reliable base engine without the need for a radiator and water cooling.
« Last Edit: April 03, 2011, 04:40:16 pm by Abraham Gubler »
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Offline PMN1

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Re: Sentinel ACIV
« Reply #19 on: October 23, 2012, 01:57:31 pm »


The AC1 Sentinel had three Cadillac 75 V8 engines (the famous car engine built in Australia by GM Holden) mounted in a cloverleaf with one on the centreline aft and two port and starboard amidships with shafts from each engine running forward to a transverse transfer box mounted under the turret basket (see picture AC1.png). The combined power of the engines was then shafted forward to the transmission via a single, centreline shaft with an output of 330 hp. Interestingly in the engine bay the three engines, radiators, fans and fuel tanks were all mounted on a common subframe and could be lifted in and out of the engine bay together.

The next variant the AC Mk 3 Thunderbolt (AC Mk 2 was a design study only for a very different tank) armed with the 25 Pounder (88mm) medium velocity gun kept the three engines but in a totally different arrangement. The three Cadillac 75 engines were mounted radially on a single triangular steel case (AC3_1.png) where they shared a common crankcase and integral transfer box. This radial mount was designed by French tank designer Mr Perrier who had been in Japan on loan from the French Government in 1940 before making his way to Australia. When fitted with the three engines the single unit was known as the Perrier-Cadillac 41-75 (AC3_2.png, aft view, note the alternator on the top engine). Also added to the frame was the fans and radiators enabling a very compact single unit without the need for the bulky under turret transfer case and subsequent power loss (AC3_3.png, forward view, note the single transmission shaft attachment below the fans). A single shaft ran under the turret floor forward to the transmission on the AC3 (AC3_4.png) with an output of just under 400 hp.

The AC Mk 4 armed with the 17 Pounder (76mm) high velocity gun was to have kept the Perrier-Cadillac 41-75 in at least the initial versions. A new engine was under development combining four Gipsy Major I4 engines (built in Australia by GM Holden for the de Havilland Australia Tiger Moth production line). This arrangement would have the potential for around 500 hp output using a very simple and reliable base engine without the need for a radiator and water cooling.

What were the weights and dimensions of these three multiple power units (particularly the Gipsy Major option) compared to the Liberty engine and the Bedford Twin 6?
« Last Edit: October 23, 2012, 02:02:33 pm by PMN1 »

Offline Abraham Gubler

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Re: Sentinel ACIV
« Reply #20 on: October 24, 2012, 07:53:52 pm »
What were the weights and dimensions of these three multiple power units (particularly the Gipsy Major option) compared to the Liberty engine and the Bedford Twin 6?

 
There is no widely published data as to the gross weight of the Perrier-Cadillac three engine unit or the proposed quad Gipsy Major. This information is no doubt archived in the Australian Cruiser files but no one has looked it up and published it. The initial cloverleaf Cadillac arrangement was never considered a single unit as it was three separate engines and only mounted on a common tray for ease of removal. However the Cadillac 75 and Gipsy Major were very common engines and I’m sure their dry weights are easy enough to find. Also the weight for the steel case for the Perrier-Cadillac mounting frame could be deduced by calculating its dimensions if someone was really keen.
 
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Offline Pioneer

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Re: Sentinel ACIV
« Reply #21 on: October 26, 2012, 01:35:34 am »
Yes it's a great pity that Australia never had the sense or tenacity to put the Sentinel series into serious production!
It's unfortunate that it is one of our traits as a nation - as a people, that we have continuously given into the negativity of our own capabilities and capacity to develop indigenous weapons/weapons systems.
With the exception of only but a hand full of weapons, Australia has always looked at the easy option (and political pressure) to buy surplus weapons or 'weapons of compatibility with our allies'
We'd sooner give up home-grown expertise and the cultivation of home-grown R&D and manufacturing to line the pockets of foreign corporations.

P.S. I apologize for my rant in advance !!

I recall reading the irony that Australia was able to build the Sentinel, before it built its first cars!

There can be no argument that the indecisiveness of the Australian Army in the way of deciding on the Sentinel's gun type/size - hence turret size ............ contributed greatly and detrimentally to the Sentinel tank design being placed into serious production and combat operations  >:(

The Sentinel's metal casting was only possible at the time, due to the skill and knowledge of the railways industry, who had developed this skill in manufacturing cast iron boilers for steam trains!

Sadley at the end of the Second World War "much of the Australian army's WWII equipment [armoured vehicles] had been sold off in vast quantities............ Despite the immediate post war plans the Australian Army had to soldier on with vehicles long since obsolete in their country or origin" [Matilda infantry tanks, Grant medium tanks and M3A1 White scout cars.](source: 50 Years of the Royal Australian Armoured Corps)     
                                                                                                                         
Even sadder (well I dare say pathetically), by the outbreak of the Korean War, the most modern of tanks that Australia fielded was the Churchill tank, which they dared not deploy [through a combination of well known obsolescence and server lack of spare parts and serviceability]. Pathetically, the Australian Army would not receive a new and modern combat efficient tank in the form of the excellent Centurion Mk.3's. I can not but help wonder how had the resolution of both Australian politician's and Army top brass been such as to have the foresight and intelligence to seriously consider the need of its army (and potential of its manufacturing potential), that if they had of seriously supported this indigenous tank design, the Australian Army could have been far more combat self efficient, not just in its own defence, but also in its sensible requirement to provide tank / direct fire support to its own troops in Korea, instead of having to risk/rely on allies armour!         
but during the Korean War, if they had of opted for the Sentinel to go into production and active service! I wonder how it would have gone against the T-34?

Early this year, I was privileged to be able to climb in to and over the Sentinel at the Armoured museum at Pukapunyal. I was greatly impressed with its thickness of armour and reasonably low silhouette, when compared to other tanks at the museum. I'll have to find them pics.........

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Mans nobility, made transcendent in the fiery crucible of war.
Faithfulness and fortitude.
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Offline Kadija_Man

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Re: Sentinel ACIV
« Reply #22 on: October 26, 2012, 11:10:13 pm »
 A.T.Ross in his book, "Army and Ready" makes it clear that the Sentinel was not suitable nor required when there were more than sufficient overseas vehicles to fulfil the role.  It was not intended to defend Australia it was intended to fight the Germans in North Africa, not the Japanese.  As Australia's commitment to that theatre was already winding down and there were sufficient vehicles already in theatre or on their way there.  We also able to source tanks for our own defence as well, which were cheaper than producing our own.  It was an expensive project which would have consumed resources which were better employed elsewhere.

Offline JFC Fuller

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Re: Sentinel ACIV
« Reply #23 on: January 26, 2013, 11:09:38 am »
This picture was posted at anther forum and is purported to show a Sentinel hull with the prototype torsion-bar suspension. I have always been very fond of the sentinel design, as pointed out in this thread it proved easy to up-gun and seems to have been very logically designed. If it had been combined with the Meteor engine it could have been an incredible tank for its time. 

Offline Abraham Gubler

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Re: Sentinel ACIV
« Reply #24 on: January 26, 2013, 04:56:51 pm »
 
If it had been combined with the Meteor engine it could have been an incredible tank for its time.

The Sentinel tank wasn’t held back by its engine in the likely war production versions (Mks 3 and 4) the Perrier-Cadillac three engine unit or the proposed quad Gipsy Major produced adequate power, were easy to manufacture and would have had the advantage (compared to the Meteor) of clutching out 2 (or 3) engines for low power needs. The biggest problem the Sentinel had was the lack of a combat opportunity. If the Japanese had been wise enough not to join WWII then Sentinels probably would have seen combat in North Africa with the 1st Australian Armoured Division. Or if the Japanese had been foolish enough to invade Australia in 1942/43 the Sentinel would have been available to drive them back into the sea.
 
I find the retrospective arguments that the Sentinel was a waste of effort like in the terrible book “Fallen Sentinel - Australian Tanks in World War II” by Peter Beale particularly disingenuous (or just plain stupid). It was a tank program launched at a time when the Empire desperately needed tanks and there was no guarantee or suggestion that the Americans would continue to supply war material after the exhaustion of British credit (Lend Lease). While Japanese entry into the war naturally ended any chance of Australian ordnance going overseas Sentinel then provided the assurance of a continental defence that would defeat Japanese invasion. While this never happened it was a pretty bloody important assurance to the Australian government.
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Offline JFC Fuller

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Re: Sentinel ACIV
« Reply #25 on: January 27, 2013, 01:57:56 am »
The Meteor would have provided an additional 20% power over the proposed Gipsy unit and probably a more compact installation; space that could have been used for additional fuel and power that could have been used for additional protection. Certainly in the types as-built form power was not an issue more powerful could have produced a better overall platform.

Offline Abraham Gubler

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Re: Sentinel ACIV
« Reply #26 on: January 27, 2013, 02:07:42 am »
The Meteor would have provided an additional 20% power over the proposed Gipsy unit and probably a more compact installation; space that could have been used for additional fuel and power that could have been used for additional protection. Certainly in the types as-built form power was not an issue more powerful could have produced a better overall platform.

The Meteor would require a coolant radiator system where the other motors were all air cooled. If more power was needed the solution was bigger motors on the Perrier frame. Which is why they were proposing the Gipsy Major to replace the Caddilac.
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Offline JFC Fuller

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Re: Sentinel ACIV
« Reply #27 on: January 27, 2013, 02:53:15 am »
The Meteor would require a coolant radiator system where the other motors were all air cooled. If more power was needed the solution was bigger motors on the Perrier frame. Which is why they were proposing the Gipsy Major to replace the Caddilac.

So the question becomes whether the more compact nature of the Meteor, combined with 20% greater power over and above even the Gipsy configuration would more than offset the need for a liquid over air-cooled system. I suspect it would have. incidentally, the ACIII may well have sacrificed the ability to clutch different engines in an out by effectively turning them into a common unit running through a common crankcase.
« Last Edit: January 27, 2013, 03:25:33 am by JFC Fuller »

Offline royabulgaf

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Re: Sentinel ACIV
« Reply #28 on: January 27, 2013, 10:47:52 am »
A few items: IRT the clover leaf engine, Chrysler in the US had a similar project, the Multibank, using five six cylinder auto engines.  It powered the M4A6 tank, which was mostly unloaded on lend-lease recipients.   The idea of shipping Sentinels to North Africa or wherever the European theater would be presuming Japan stayed neutral, was unworkable.   The supply line would be easily several months long, and at that time there simply was not the tonnage to spare.  The smart thing to do would be supply Australian armor units in Europe out of British stocks, and supply Commonwealth units in south Asia with Sentinels or whatever.

Offline Kadija_Man

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Re: Sentinel ACIV
« Reply #29 on: January 27, 2013, 06:53:54 pm »
I find the retrospective arguments that the Sentinel was a waste of effort like in the terrible book “Fallen Sentinel - Australian Tanks in World War II” by Peter Beale particularly disingenuous (or just plain stupid). It was a tank program launched at a time when the Empire desperately needed tanks and there was no guarantee or suggestion that the Americans would continue to supply war material after the exhaustion of British credit (Lend Lease). While Japanese entry into the war naturally ended any chance of Australian ordnance going overseas Sentinel then provided the assurance of a continental defence that would defeat Japanese invasion. While this never happened it was a pretty bloody important assurance to the Australian government.

The problem for Sentinel was that it was launched at a time when the only physical enemy were the Germans in North Africa.   Because of the rapid evolution of the AFVs in that conflict, it was always, like the other Allied tanks always going to be playing catch-up.  While it had the potential to do so, the small numbers which were going to be produced were always going to be uneconomic.  Their costs would be disproportionately high and the costs of maintaining them so far from home would also be hight because of the lack of commonality with the other Allied AFVs which would have predominated in that theatre.  The UK was never going to adopt it, both because of it's source and because it was cheaper and easier to source already built AFVs, like most other military materiale from either home or the USA.   This was obvious even at the time, if the Australian Army had been willing to open its eyes.

Because it was designed to counter the Germans' AFVs it was more difficult to manufacture than one which was designed to counter the real enemy which did eventuate - the Japanese.  As their AFVs were light and had little armour, a much lighter vehicle could have been used but because the Army had decided on one designed for North Africa, the result was a vehicle that was expensive, both in material and manpower to produce.  In the end, the choice was either tanks or light ships and aircraft.  Tanks are excellent for defence of the mainland, less useful in the Islands.  As by the time the Sentinel reached production, US AFVs were available in quantity and cheaply, it was obvious what would happen.

Romantics might like to think we should have produced them but much more hard-headed men decided otherwise.  With the winding down of the commitment to North Africa and the withdrawal of Australian troops to home defence and then the offensive against the Japanese, the need for Sentinel had all but disappeared.  If we had produced them in the numbers desired, the offensive against the Japanese would have been stalled (at least from an Australian perspective) as we would not have had the light ships, nor the aircraft to carry that offensive to the enemy.   It might be felt that these arguments are made in hindsight but they were considered at the time, which is of course why the Sentinel failed to be produced in the quantities that some feel they should have.

The same romantics still believe perhaps that it was likely that the Japanese were to invade or even directly attack in force the mainland.   While it wasn't known with absolute surety at the time, the succession of invasion scares and defensive strategy arguments which occur had more to do with domestic politics than they did with the reality of both what the Japanese were capable of and what they actually did.   The remote threat that the Japanese represented could be countered more cheaply and easily with imported AFVs.  As the Lee/Grant and Matilda were obsolescent against the European enemy, they were ideal against the Japanese one.


Offline Abraham Gubler

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Re: Sentinel ACIV
« Reply #30 on: January 27, 2013, 07:54:01 pm »
 
The problem for Sentinel was that it was launched at a time when the only physical enemy were the Germans in North Africa. Because of the rapid evolution of the AFVs in that conflict, it was always, like the other Allied tanks always going to be playing catch-up.

So that’s a problem facing every weapon system ever developed, everwhere.
 
While it had the potential to do so, the small numbers which were going to be produced were always going to be uneconomic.

Sentinel was planned for mass production through two new plants (one built in Sydney, one planned in Melbourne) using mass production items (motors, guns, etc.). Far from being a small production run of uneconomic vehicles.
 
Their costs would be disproportionately high and the costs of maintaining them so far from home would also be hight because of the lack of commonality with the other Allied AFVs which would have predominated in that theatre. The UK was never going to adopt it, both because of it's source and because it was cheaper and easier to source already built AFVs, like most other military materiale from either home or the USA. This was obvious even at the time, if the Australian Army had been willing to open its eyes.

It wasn’t obvious because there was no guarantee of supply to North Africa from both the UK and certainly the USA. Australia had more resilient lines of communication to North Africa that the Germans couldn’t interdict.
 
Because it was designed to counter the Germans' AFVs it was more difficult to manufacture than one which was designed to counter the real enemy which did eventuate - the Japanese. As their AFVs were light and had little armour, a much lighter vehicle could have been used but because the Army had decided on one designed for North Africa, the result was a vehicle that was expensive, both in material and manpower to produce.

Yet the Stuart light tank was proven to be inadequate in jungle operations and was replaced by the heavy Matilda. Tanks used against the Japanese in the Pacific Islands campaign very rarely encountered their tanks. But their anti-tank weapons and artillery were punishing to Allied medium tanks. But the tanks were also decisive in winning battles. Saying only light tanks were needed is a very amateurish tank argument.
 
Romantics might like to think we should have produced them but much more hard-headed men decided otherwise.

No one here is suggesting they should have been built after the stabilisation of war in 1943.
 
The same romantics still believe perhaps that it was likely that the Japanese were to invade or even directly attack in force the mainland. While it wasn't known with absolute surety at the time, the succession of invasion scares and defensive strategy arguments which occur had more to do with domestic politics than they did with the reality of both what the Japanese were capable of and what they actually did. The remote threat that the Japanese represented could be countered more cheaply and easily with imported AFVs. As the Lee/Grant and Matilda were obsolescent against the European enemy, they were ideal against the Japanese one.

So by your own words you think preparing to counter an invasion that you didn’t know “with absolute surety” was not going to happen is “romantic”? Please whatever you do in life, please stay away from risk assessment! An invasion is the worst thing that could have happened even if there was only a slim chance of it going ahead (and at the time there was strong indication it was very likely) justified the huge effort the Australian nation put into countering it:
 
Brown, Gary; Anderson, David (1992). "Invasion 1942? Australia and the Japanese Threat". Background Paper Number 6 1992. Department of the Parliamentary Library.
Horner, David (1993). "Defending Australia in 1942". The Pacific War 1942. Canberra: Department of History, Australian Defence Force Academy.
Stanley, Peter (2002). "He’s (not) Coming South": the invasion that wasn’t" (PDF). Conference Papers. Remembering 1942.
Stanley, Peter (2008). Invading Australia. Japan and the Battle for Australia, 1942. Melbourne: Penguin Group (Australia).
 
I think your claims that others are ‘romantic’ is as misguided as your attempt to pass yourself off as a combat veteran with your new alternate nick (Kadija Man was Rickshaw) while you were banned from posting.
 
I have several medals to show that indeed I have "humped this stuff downrange" on a two-way rifle range, thank you very much.

Military imposters make me sick. Applying hindsight to make calls against contemporary decision making is not so sickening, just plain dumb.
« Last Edit: January 27, 2013, 08:08:06 pm by Abraham Gubler »
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Offline Abraham Gubler

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Re: Sentinel ACIV
« Reply #31 on: January 27, 2013, 07:59:07 pm »
 
So the question becomes whether the more compact nature of the Meteor, combined with 20% greater power over and above even the Gipsy configuration would more than offset the need for a liquid over air-cooled system. I suspect it would have. incidentally, the ACIII may well have sacrificed the ability to clutch different engines in an out by effectively turning them into a common unit running through a common crankcase.

Even in the common frame mounting (Perrier) the engines could be clutched out. But without the full data on weight and so on it’s a hard call to make which would be better. Certainly the Cadillac and Gipsy Major engines were being manufactured in Australia in 1940 while the Merlin (and a potential Meteor) wasn’t until 1944-46. I would suspect however despite multiple motors maintenance in the Perrier arrangements would be much lower than a single Meteor. The Cadillac and Gipsy Major engines were well known as two of the most reliable motors in the world at the time and Meteor plus coolant system was a well-known fitter magnet.
"There is a tendency in our planning to confuse the unfamiliar with the improbable." Thomas Schelling

Offline Abraham Gubler

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Re: Sentinel ACIV
« Reply #32 on: January 27, 2013, 08:05:09 pm »
 
The idea of shipping Sentinels to North Africa or wherever the European theater would be presuming Japan stayed neutral, was unworkable. The supply line would be easily several months long, and at that time there simply was not the tonnage to spare. The smart thing to do would be supply Australian armor units in Europe out of British stocks, and supply Commonwealth units in south Asia with Sentinels or whatever.

The supply line to Egypt from Australia was actually much shorter and far less risker than from the UK to Egypt in 1940-42 It was 20,000 km from the UK to Egypt around the Cape of Good Hope through the U Boat infested Atlantic. From Australia (Sydney) to Egypt it is only 15,000 km through much safer waters.
"There is a tendency in our planning to confuse the unfamiliar with the improbable." Thomas Schelling

Offline Kadija_Man

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Re: Sentinel ACIV
« Reply #33 on: January 27, 2013, 10:09:21 pm »
The problem for Sentinel was that it was launched at a time when the only physical enemy were the Germans in North Africa. Because of the rapid evolution of the AFVs in that conflict, it was always, like the other Allied tanks always going to be playing catch-up.

So that’s a problem facing every weapon system ever developed, everwhere.

True but as Australia was operating invariably on second if not more often third-hand information about technical matters in the North African desert, it would have been worse.   We were at the end of the intelligence food-chain, with reports arriving months, often years after they had been digested in London or Washington.  Nor, unfortunately was our military bureaucracy noted for its speedy or necessarily wise decision making. 
 
Quote
While it had the potential to do so, the small numbers which were going to be produced were always going to be uneconomic.

Sentinel was planned for mass production through two new plants (one built in Sydney, one planned in Melbourne) using mass production items (motors, guns, etc.). Far from being a small production run of uneconomic vehicles.

Total numbers would still have been small.   Our demand for tanks was small as we did not have a disproportionate number of armoured units and formations which required them.  Therefore, unit cost would have been higher than a comparable vehicle imported from the US or even the UK, even taking into account transport costs.

Quote
Their costs would be disproportionately high and the costs of maintaining them so far from home would also be hight because of the lack of commonality with the other Allied AFVs which would have predominated in that theatre. The UK was never going to adopt it, both because of it's source and because it was cheaper and easier to source already built AFVs, like most other military materiale from either home or the USA. This was obvious even at the time, if the Australian Army had been willing to open its eyes.

It wasn’t obvious because there was no guarantee of supply to North Africa from both the UK and certainly the USA. Australia had more resilient lines of communication to North Africa that the Germans couldn’t interdict.

You're forgetting that until 1941, the entrance to the Red Sea was contested by Italy.  All it needed was for Germany to reinforce Ethiopia with Luftwaffe units and the Red Sea would have been closed.
 
Quote
Because it was designed to counter the Germans' AFVs it was more difficult to manufacture than one which was designed to counter the real enemy which did eventuate - the Japanese. As their AFVs were light and had little armour, a much lighter vehicle could have been used but because the Army had decided on one designed for North Africa, the result was a vehicle that was expensive, both in material and manpower to produce.

Yet the Stuart light tank was proven to be inadequate in jungle operations and was replaced by the heavy Matilda. Tanks used against the Japanese in the Pacific Islands campaign very rarely encountered their tanks.

I would contend that was a poor choice of vehicle for that terrain, not necessarily that the Stuart was a bad tank for use against the Japanese.  It would have been ideal for use on the continent, if the Japanese had ever  attempted to attack or invade.   Small, light, fast, well armed, reliable, it would have been a good vehicle considering the loading difficulties that narrow gauge railways in Queensland and central Australia had with heavier loads. 

Quote
But their anti-tank weapons and artillery were punishing to Allied medium tanks. But the tanks were also decisive in winning battles. Saying only light tanks were needed is a very amateurish tank argument.

But they did not have many of either.  AT defence was not given much emphasis by the Japanese.  If, as you suggest they were "punishing to Allied medium tanks" they would have been "punishing to Allied lighter tanks" as well, so it would have made no difference, now would it?
 
Quote
Romantics might like to think we should have produced them but much more hard-headed men decided otherwise.

No one here is suggesting they should have been built after the stabilisation of war in 1943.

Why build them before?  The allocation of resources would have slowed the build up of the small ships and aero industries.  By the time full production had started - mid-late 1942, the "stabilisation" would have just been around the corner.

Quote

The same romantics still believe perhaps that it was likely that the Japanese were to invade or even directly attack in force the mainland. While it wasn't known with absolute surety at the time, the succession of invasion scares and defensive strategy arguments which occur had more to do with domestic politics than they did with the reality of both what the Japanese were capable of and what they actually did. The remote threat that the Japanese represented could be countered more cheaply and easily with imported AFVs. As the Lee/Grant and Matilda were obsolescent against the European enemy, they were ideal against the Japanese one.

So by your own words you think preparing to counter an invasion that you didn’t know “with absolute surety” was not going to happen is “romantic”? Please whatever you do in life, please stay away from risk assessment! An invasion is the worst thing that could have happened even if there was only a slim chance of it going ahead (and at the time there was strong indication it was very likely) justified the huge effort the Australian nation put into countering it:
 
Brown, Gary; Anderson, David (1992). "Invasion 1942? Australia and the Japanese Threat". Background Paper Number 6 1992. Department of the Parliamentary Library.
Horner, David (1993). "Defending Australia in 1942". The Pacific War 1942. Canberra: Department of History, Australian Defence Force Academy.
Stanley, Peter (2002). "He’s (not) Coming South": the invasion that wasn’t" (PDF). Conference Papers. Remembering 1942.
Stanley, Peter (2008). Invading Australia. Japan and the Battle for Australia, 1942. Melbourne: Penguin Group (Australia).

Read them all.  None of them pay particular attention to the economic issues.  I recommend to you A.T. Ross, Armed &​ ready : the industrial development &​ defence of Australia, 1900-1945, Turton &​ Armstrong. Wahroonga, 1995.  Moreover, A.T. Ross discusses at length the issues surrounding the Sentinel and its troublesome gestation and its intended usefulness.

As the old adage goes, "amateurs study strategy, professionals study logistics" and by extension economics.

As to the surety or otherwise of a Japanese invasion, by late 1942 it was obvious the tide was turning and Japan was overstretched.   By then, nearly all Australia's combat forces had returned (bar one Division) from the Middle East.  They were battle-hardened, well trained and moderately well equipped for the very sort of battle an invasion would result in, one of manoeuvre in open countryside.  Something the Japanese had been shown to be rather badly trained and equipped for at Khalkhin Gol.  After the end of 1942, the Japanese were essentially on the defensive in the Pacific.   It was the invasion scare of 1943 and the Defensive Strategy controversy which left many Australians with the mistaken belief as to what Japan's intentions were.

There is a very good, short discussion in fact of that in the recent book, Craig Collie and Hajime Marutani, The path of Infinite Sorrow: The Japanese on the Kokoda Track, Allen and Unwin, Sydney, 2012.  It is an excellent read in it's own right and places the Japanese aspect of the campaign into perspective very well.


Offline Abraham Gubler

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Re: Sentinel ACIV
« Reply #34 on: January 27, 2013, 11:10:40 pm »
 
True but as Australia was operating invariably on second if not more often third-hand information about technical matters in the North African desert, it would have been worse. We were at the end of the intelligence food-chain, with reports arriving months, often years after they had been digested in London or Washington. Nor, unfortunately was our military bureaucracy noted for its speedy or necessarily wise decision making.

That is unsubstantiated and incorrect. Australian technical intelligence of the battlefield was supplied via the Australian Army’s independent command chain. Far from being behind the times Australia was as well informed of tank developments which is why the Sentinel was redesigned and updated at a rate faster than the British tank program.
 
Total numbers would still have been small. Our demand for tanks was small as we did not have a disproportionate number of armoured units and formations which required them. Therefore, unit cost would have been higher than a comparable vehicle imported from the US or even the UK, even taking into account transport costs.

Small as in several thousand if full rate production had gone ahead in 1942-45 (planed rate of 70 per month)? Small by Soviet, American or British standards but not uneconomic which was your initial point. Gross cost may have been higher thanks to Australia having to pay for establishment of the production facilities - a cost not passed on via Allied production - but unit cost to build would be comparable. This is another unsubstantiated non argument.
 
You're forgetting that until 1941, the entrance to the Red Sea was contested by Italy. All it needed was for Germany to reinforce Ethiopia with Luftwaffe units and the Red Sea would have been closed.

Ahh so then how did the North African forces get their logistics from the UK? It certainly didn’t come via the Mediterranean or over land via the Sudan. It all came up the Red Sea, after having gone around the Cape, past Italy’s rapidly collapsing East African Front. Another non-issue, non-logical to if you’d bothered to think about it rather than leap at any factoid that may appear to batter my opinions.
 
I would contend that was a poor choice of vehicle for that terrain, not necessarily that the Stuart was a bad tank for use against the Japanese. It would have been ideal for use on the continent, if the Japanese had ever attempted to attack or invade. Small, light, fast, well armed, reliable, it would have been a good vehicle considering the loading difficulties that narrow gauge railways in Queensland and central Australia had with heavier loads.

More non issues. There are no loading issues associated with Queensland railways. Narrow gauge or Cape gauge isn’t toy trains they carry the same loads as other trains. Just that the rails are closer together so they can turn sharper corners and cost less to install.
 
But they did not have many of either. AT defence was not given much emphasis by the Japanese. If, as you suggest they were "punishing to Allied medium tanks" they would have been "punishing to Allied lighter tanks" as well, so it would have made no difference, now would it?

Actually it doesn’t work that way. Light tanks would – and did – suffer *more* punishment from Japanese anti tank defence because they have less armour. Another non issue, based on the semantics of the adjective I used!
 
Why build them before? The allocation of resources would have slowed the build up of the small ships and aero industries. By the time full production had started - mid-late 1942, the "stabilisation" would have just been around the corner.

Because there was no supply of tanks available from the UK for the Australian armoured units! How many times do we have to cover this same material just because you don’t get it? Australian armoured units can’t be equipped with aircraft or small ships. The air force and navy didn’t seem to have a problem before 1942 with their plane and ship supply. The RAAF was actually saying no to RAF suggestions of transferring US contracts. The Navy was building the AMS in numbers faster than they could crew. Of course in hindsight it would have been better for these two services to be building fighters and torpedo boats in Australia in 1940-41 but they didn’t want to because they didn’t think they had the need. You should be thankful the Army established new tank production capability that could later be used to sustain the large allied landing craft fleet because otherwise such capability wouldn’t have existed.
 
Read them all. None of them pay particular attention to the economic issues. I recommend to you A.T. Ross, Armed &​ ready : the industrial development &​ defence of Australia, 1900-1945, Turton &​ Armstrong. Wahroonga, 1995. Moreover, A.T. Ross discusses at length the issues surrounding the Sentinel and its troublesome gestation and its intended usefulness.
 
 As the old adage goes, "amateurs study strategy, professionals study logistics" and by extension economics.

Ross’s arguments about the Sentinel are loaded by hindsight. I actually worked with the man during the time he wrote this book so it’s hardly new to me. I quoted those sources to make fun of your ridiculous claims about how the invasion threat was just some political issue not something to be taken seriously. That you changed the context is no surprise.
 
As to the surety or otherwise of a Japanese invasion, by late 1942 it was obvious the tide was turning and Japan was overstretched. By then, nearly all Australia's combat forces had returned (bar one Division) from the Middle East. They were battle-hardened, well trained and moderately well equipped for the very sort of battle an invasion would result in, one of manoeuvre in open countryside. Something the Japanese had been shown to be rather badly trained and equipped for at Khalkhin Gol. After the end of 1942, the Japanese were essentially on the defensive in the Pacific. It was the invasion scare of 1943 and the Defensive Strategy controversy which left many Australians with the mistaken belief as to what Japan's intentions were.

LOL. So you’re claiming that the improved security situation in late 1942/43 should have determined defence equipment decisions made in late 1941, early 1942? In early 1943 decisions were made to stop the Australian counter invasion preparations. To assume that a year previous the Government and Army leadership should have been aware things would be much better in a year or so is ridiculous. But why stop at Australia? Surely by this rational Churchill was just blowing smoke when he declared that they would fight them on the beaches? How much wasted resources were put into counter invasion defences in the UK in 1940? In Rickshaw/Kadija world that was all wasted effort…
« Last Edit: January 28, 2013, 01:58:41 am by Abraham Gubler »
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Offline Pioneer

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Re: Sentinel ACIV
« Reply #35 on: January 28, 2013, 01:27:34 am »
A couple of years ago, I took my son and his mate to Puckapunyal Armoured Museum, where took this photo of them in front of a SentinelOne thing that stood out to the boys was its cast construction method and the thickness of its armour!   RegardsPioneer
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Offline Abraham Gubler

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Re: Sentinel ACIV
« Reply #36 on: January 28, 2013, 01:36:26 am »
A couple of years ago, I took my son and his mate to Puckapunyal Armoured Museum, where took this photo of them in front of a SentinelOne thing that stood out to the boys was its cast construction method and the thickness of its armour!   RegardsPioneer

Great photos. The boys look the right size to be 'hull beast' crew.  :D
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Offline JFC Fuller

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Re: Sentinel ACIV
« Reply #37 on: January 28, 2013, 01:41:40 am »
I would like to see a source about the ACIII engine allowing certain cylinders to clutch out; I have only seen this claim made for the original ACI clover leaf configuration, it easy to see how that would have worked as each engine ran through its own clutch before reaching the transfer case, obviously that is not the case on the ACIII configuration. The base Cadillac and Gipsy motors may have been reliable but generally speaking, combining a collection of smaller motors tends not to enhance reliability- though there are of course very reliable multi-bank engines. The Meteor became a highly successful tank engine and offered 20% + more power than even the proposed Gipsy configuration.

Offline JFC Fuller

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Re: Sentinel ACIV
« Reply #38 on: January 28, 2013, 01:43:23 am »
Pioneer,

Great photos, thanks for posting. The flat-fronted ACIII configuration without the bow-gunner looks even better. :P

Offline Abraham Gubler

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Re: Sentinel ACIV
« Reply #39 on: January 28, 2013, 01:54:27 am »
 
I would like to see a source about the ACIII engine allowing certain cylinders to clutch out; I have only seen this claim made for the original ACI clover leaf configuration, it easy to see how that would have worked as each engine ran through its own clutch before reaching the transfer case, obviously that is not the case on the ACIII configuration.

Bad use of language on my behalf there were no separate clutches but each engine unit could still be turned on and off separately despite being mounted on a single case.
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Offline Abraham Gubler

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Re: Sentinel ACIV
« Reply #40 on: January 28, 2013, 02:19:30 am »
Here's a very bad scan (not my fault) of a blue print of the planned AC3 production tank. Has quite  different turret shape to the AC1.
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Offline robunos

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Re: Sentinel ACIV
« Reply #41 on: January 28, 2013, 09:26:00 am »
Quote
...AC Mk 2 was a design study only for a very different tank...

Does anyone have any more on this design......?

cheers,
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Offline Kadija_Man

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Re: Sentinel ACIV
« Reply #42 on: January 28, 2013, 10:55:57 pm »
Quote
...AC Mk 2 was a design study only for a very different tank...

Does anyone have any more on this design......?

cheers,
            Robin.

A.T.Ross describes AC II as having been a much lighter armoured vehicle than AC I, based around IIRC the use of commercial truck mechanical components for the drive train and armed with a 2 Pdr.  He believed it would have been a much more useful and more easily built vehicle than what became the Sentinel.  However, he also notes the difficulties where other such vehicles attempted to use such drive trains in their design.

Offline Kadija_Man

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Re: Sentinel ACIV
« Reply #43 on: January 29, 2013, 12:07:45 am »
True but as Australia was operating invariably on second if not more often third-hand information about technical matters in the North African desert, it would have been worse. We were at the end of the intelligence food-chain, with reports arriving months, often years after they had been digested in London or Washington. Nor, unfortunately was our military bureaucracy noted for its speedy or necessarily wise decision making.

That is unsubstantiated and incorrect. Australian technical intelligence of the battlefield was supplied via the Australian Army’s independent command chain. Far from being behind the times Australia was as well informed of tank developments which is why the Sentinel was redesigned and updated at a rate faster than the British tank program.
 
Total numbers would still have been small. Our demand for tanks was small as we did not have a disproportionate number of armoured units and formations which required them. Therefore, unit cost would have been higher than a comparable vehicle imported from the US or even the UK, even taking into account transport costs.

Small as in several thousand if full rate production had gone ahead in 1942-45 (planed rate of 70 per month)? Small by Soviet, American or British standards but not uneconomic which was your initial point. Gross cost may have been higher thanks to Australia having to pay for establishment of the production facilities - a cost not passed on via Allied production - but unit cost to build would be comparable. This is another unsubstantiated non argument.

It is noted in several works that a great deal of technical intelligence came from London to Australia, from the Middle East or Europe.  Be it on enemy aircraft, armoured vehicles or ships.  The AIF HQ in the Middle-East liased closely with their counterparts in the British HQ but those counterparts often produced only initial reports based upon their examination of captured equipment, whereas the War Office produced its own reports which were more wide ranging.   I don't have references to hand but I am sure I've read that in several technical books that "information received" was often months, sometimes years after the event.

Quote

You're forgetting that until 1941, the entrance to the Red Sea was contested by Italy. All it needed was for Germany to reinforce Ethiopia with Luftwaffe units and the Red Sea would have been closed.

Ahh so then how did the North African forces get their logistics from the UK? It certainly didn’t come via the Mediterranean or over land via the Sudan.

Well, to reach Sudan, they'd have to transit the entrance to the Red Sea anyway.  How did they do it?  By running the gauntlet.  Not that it was that much of a gauntlet I admit.  Air cover was provided from Aden by the RAF.  Even so, the Italians had several ships and submarines based in the Horn of Africa, as well as many aircraft.

Quote
It all came up the Red Sea, after having gone around the Cape, past Italy’s rapidly collapsing East African Front. Another non-issue, non-logical to if you’d bothered to think about it rather than leap at any factoid that may appear to batter my opinions.

A "rapidly collapsing East African front" that I would point out lasted until November 1941 (with the Allied campaign therein lasting from June 1940 to November 1941).   Didn't appear to all that rapid, really, although the final stages I admit, were pretty quick.  So, effectively we had a window of less than a month between the collapse of the Italians in the Horn of Africa to when the war with the Japanese began, when supplies were unlikely to be molested (except of course by the occasional German raider) in the Indian Ocean.

Quote

I would contend that was a poor choice of vehicle for that terrain, not necessarily that the Stuart was a bad tank for use against the Japanese. It would have been ideal for use on the continent, if the Japanese had ever attempted to attack or invade. Small, light, fast, well armed, reliable, it would have been a good vehicle considering the loading difficulties that narrow gauge railways in Queensland and central Australia had with heavier loads.

More non issues. There are no loading issues associated with Queensland railways. Narrow gauge or Cape gauge isn’t toy trains they carry the same loads as other trains. Just that the rails are closer together so they can turn sharper corners and cost less to install.

Wheel loading on trains and rail bed construction though, is.   Narrow gauge trains have much lower loading limits for that very reason.  The very reason why narrow gauge was adopted in Australia - cheapness - ensured that they could not carry as much load as either standard or broad gauge.   Such factors must be considered when undertaking such study.  The end result would be that twice as many flat trucks would be required, per unit load as only one medium tank could be carried as against two lighter tanks.   

Quote
But they did not have many of either. AT defence was not given much emphasis by the Japanese. If, as you suggest they were "punishing to Allied medium tanks" they would have been "punishing to Allied lighter tanks" as well, so it would have made no difference, now would it?

Actually it doesn’t work that way. Light tanks would – and did – suffer *more* punishment from Japanese anti tank defence because they have less armour. Another non issue, based on the semantics of the adjective I used!

BUT as I pointed out, AT defence was a lower priority with the Japanese because they had not encountered large numbers of armoured vehicles in their wars in Asia. Even when they had, as at Khalkhyn Gol, no higher priority was placed on it.  This meant that tanks were less likely to meet an AT gun or an Artillery piece which had been re-rolled to AT duties.  As these could be easily outflanked and overrun in the broad, open spaces of Australia than they could in the narrow confines of the Tropical Rainforests of the Pacific Islands, light tanks would IMO have been sufficient, if used in large numbers to attack and defeat Japanese forces - exactly as the Russians had done at Khalkhyn Gol.

The Japanese were not supermen.  They were in many ways even more fallible than most in their belief in their racial and moral superiority, which led them to be more rigid in their adherence to their set piece tactics.

Quote

Why build them before? The allocation of resources would have slowed the build up of the small ships and aero industries. By the time full production had started - mid-late 1942, the "stabilisation" would have just been around the corner.

Because there was no supply of tanks available from the UK for the Australian armoured units! How many times do we have to cover this same material just because you don’t get it? Australian armoured units can’t be equipped with aircraft or small ships. The air force and navy didn’t seem to have a problem before 1942 with their plane and ship supply. The RAAF was actually saying no to RAF suggestions of transferring US contracts. The Navy was building the AMS in numbers faster than they could crew. Of course in hindsight it would have been better for these two services to be building fighters and torpedo boats in Australia in 1940-41 but they didn’t want to because they didn’t think they had the need. You should be thankful the Army established new tank production capability that could later be used to sustain the large allied landing craft fleet because otherwise such capability wouldn’t have existed.

Tanks did come from the UK and in numbers.  Not directly from the UK but from British stocks in the Middle-East as the older Matilda and M3 Lee/Grants as they were replaced by newer vehicles.  M3 mediums also came directly from the USA.  The M3 was a potent vehicle compared to the Japanese tanks and performed more than adequately when deployed against the Japanese in Burma.

As for the establishment of the tank lines - you are partially correct.  However, as you yourself note, their value came not when they produced tanks but rather small craft.  Small craft which were the lynchpin of the advance through the islands.

Quote

Read them all. None of them pay particular attention to the economic issues. I recommend to you A.T. Ross, Armed &​ ready : the industrial development &​ defence of Australia, 1900-1945, Turton &​ Armstrong. Wahroonga, 1995. Moreover, A.T. Ross discusses at length the issues surrounding the Sentinel and its troublesome gestation and its intended usefulness.
 
 As the old adage goes, "amateurs study strategy, professionals study logistics" and by extension economics.

Ross’s arguments about the Sentinel are loaded by hindsight. I actually worked with the man during the time he wrote this book so it’s hardly new to me. I quoted those sources to make fun of your ridiculous claims about how the invasion threat was just some political issue not something to be taken seriously. That you changed the context is no surprise.

That is your opinion.  I beg to differ.  I note that you did not mention it, despite it having an extensive discussion of the very vehicle we are talking about.  Perhaps you merely disagreed with his conclusions?  I don't.

Quote

As to the surety or otherwise of a Japanese invasion, by late 1942 it was obvious the tide was turning and Japan was overstretched. By then, nearly all Australia's combat forces had returned (bar one Division) from the Middle East. They were battle-hardened, well trained and moderately well equipped for the very sort of battle an invasion would result in, one of manoeuvre in open countryside. Something the Japanese had been shown to be rather badly trained and equipped for at Khalkhin Gol. After the end of 1942, the Japanese were essentially on the defensive in the Pacific. It was the invasion scare of 1943 and the Defensive Strategy controversy which left many Australians with the mistaken belief as to what Japan's intentions were.

LOL. So you’re claiming that the improved security situation in late 1942/43 should have determined defence equipment decisions made in late 1941, early 1942?

The decisions in late 1941, early 1942 should have been made in light of the knowledge that Australia was not going to be "unprotected" and that the war in the Western Desert was looking more firmly to be moving towards the defeat of the Axis.   There are no sureties, I agree but what was required was calm consideration, not panicky decisions to build a tank which was not going to be required for the situation likely to be facing Australia in either the near for far future.

Quote
In early 1943 decisions were made to stop the Australian counter invasion preparations. To assume that a year previous the Government and Army leadership should have been aware things would be much better in a year or so is ridiculous. But why stop at Australia? Surely by this rational Churchill was just blowing smoke when he declared that they would fight them on the beaches? How much wasted resources were put into counter invasion defences in the UK in 1940? In Rickshaw/Kadija world that was all wasted effort…

The threat of invasion had receded by late 1942.  Bureacracy sometimes has an inertia all its own.

Offline Abraham Gubler

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Re: Sentinel ACIV
« Reply #44 on: January 29, 2013, 03:31:05 am »
 
It is noted in several works that a great deal of technical intelligence came from London to Australia, from the Middle East or Europe. Be it on enemy aircraft, armoured vehicles or ships. The AIF HQ in the Middle-East liased closely with their counterparts in the British HQ but those counterparts often produced only initial reports based upon their examination of captured equipment, whereas the War Office produced its own reports which were more wide ranging. I don't have references to hand but I am sure I've read that in several technical books that "information received" was often months, sometimes years after the event.

Of course most technical intel came from London they were involved in a lot more of the war than Australia! It’s also common for a lot of it to be late in reaching the required reader but that’s the nature of the beast not an exclusive Australian problem. But it’s a total non-issue to claim that marques of Sentinel would be behind the times because it was built in Australia and Australian’s didn’t know what was going on. They did and they updated the requirements for Sentinel accordingly on a similar if not better timetable than the British.
 
Well, to reach Sudan, they'd have to transit the entrance to the Red Sea anyway. How did they do it? By running the gauntlet. Not that it was that much of a gauntlet I admit. Air cover was provided from Aden by the RAF. Even so, the Italians had several ships and submarines based in the Horn of Africa, as well as many aircraft.

Why do you keep pushing this dead horse? The issue was lines of communication to North Africa from Australia were better than lines of communication to North Africa from Great Britain going around the Cape of Good Hope. Both lines have to pass up the Red Sea. Whatever is going on there effects both. You brought up the East African campaign as some deal breaker in my line of reasoning that Australia offered better supply lines. It didn’t so just give up already and allow the thread to move along.
 
Wheel loading on trains and rail bed construction though, is.

Which is why narrow gauge rails and beds in Australia and South Africa is built to standard gauge standards. The cheapness came in not having to make wider corners and all the required cuttings and the like. You quite clearly don’t know enough about railways to be making informed comment and are just making false arguments for an issue that didn’t exist. Breaks in gauge of course were (and are) a major impediment to Australian rail transport but loading weight is a non issue.
 
BUT as I pointed out, AT defence was a lower priority with the Japanese because they had not encountered large numbers of armoured vehicles in their wars in Asia. Even when they had, as at Khalkhyn Gol, no higher priority was placed on it. This meant that tanks were less likely to meet an AT gun or an Artillery piece which had been re-rolled to AT duties. As these could be easily outflanked and overrun in the broad, open spaces of Australia than they could in the narrow confines of the Tropical Rainforests of the Pacific Islands, light tanks would IMO have been sufficient, if used in large numbers to attack and defeat Japanese forces - exactly as the Russians had done at Khalkhyn Gol.

So your argument is light tanks were adequate for continental defence. But my point was entirely about the Pacific Islands Campaign. Your context jumping is legendary.
 
Tanks did come from the UK and in numbers. Not directly from the UK but from British stocks in the Middle-East as the older Matilda and M3 Lee/Grants as they were replaced by newer vehicles. M3 mediums also came directly from the USA. The M3 was a potent vehicle compared to the Japanese tanks and performed more than adequately when deployed against the Japanese in Burma.

These tanks didn’t exist in 1940 and were not available for Australia in 1941. This was when the decision to go ahead with the Australian Cruiser program was launched. At that time the British had said no tanks are available. Lend-lease, American entry into the way, rapid modernisation (and obsolescence of tank fleets), high risk of an invasion of Australia and two bloody years all changed this situation. Which was the context again of this point – why was the program launched in the first place.
 
I note that you did not mention it, despite it having an extensive discussion of the very vehicle we are talking about. Perhaps you merely disagreed with his conclusions? I don't.

Do you know what the word “context” means? I didn’t list that book because it was not about the issue under discussion. Which was your ridiculous claims that the threat of invasion to Australia in 1942 was a non-issue. Ross’s book is about Australian defence industry policy from 1900 to 1945! And it does spend quite some time talking about the great efforts put into place to counter the risk of invasion in 1942. But is not a strategic appreciation of the Pacific War in the Australian Theatre at this time or any other.
 
The threat of invasion had receded by late 1942. Bureacracy sometimes has an inertia all its own.
 

Well they still had the combat power to launch a full scale invasion of Darwin or Perth or somewhere in between by Japanese risk appetites. Of course with the full benefit of hindsight knowing their precarious state – strategic intelligence that only became fully apparent after the war – such an attack would have consumed the last of their offensive resources which they wanted to keep in reserve.
 
But I’m glad you’ve seen the light and reassessed your invasion threat assessment from “domestic political campaign” to something more realistic. I wonder how long the rest of your opinions will take to catch up to reality.
« Last Edit: January 29, 2013, 03:51:48 am by Abraham Gubler »
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Offline robunos

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Re: Sentinel ACIV
« Reply #45 on: January 29, 2013, 01:40:36 pm »
Quote
...AC Mk 2 was a design study only for a very different tank...

Does anyone have any more on this design......?

cheers,
            Robin.

A.T.Ross describes AC II as having been a much lighter armoured vehicle than AC I, based around IIRC the use of commercial truck mechanical components for the drive train and armed with a 2 Pdr.  He believed it would have been a much more useful and more easily built vehicle than what became the Sentinel.  However, he also notes the difficulties where other such vehicles attempted to use such drive trains in their design.

Thanks for that...
After I posted here I found this site :-

http://www.mheaust.com.au/Aust/Research/Sentinel/sentinelmk.htm

that has some information about the AC II, as well as the other AC variants.

cheers,
            Robin.
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Offline Basilisk

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Re: Sentinel ACIV
« Reply #46 on: September 22, 2015, 11:05:14 pm »

The 25 pdr armed AC3.


An idea of what the AC4 would look like.


The Gipsy Major based tank engine.

Offline Abraham Gubler

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Re: Sentinel ACIV
« Reply #47 on: September 30, 2015, 03:10:28 pm »
Great pictures Basilisk, thanks for posting them. Especially the quad Gipsy Major engine. Very shiny and chrome.

Not only was the ACIII (and IV) one of the best tanks of WWII (never built) it was also what the Australian Army needed. When the Govt. cancelled the production order they did so because they assumed, and were assured, they could get Sherman tanks via Lend Lease to replace the Matilda tanks for the campaigns of 19s 44, 45 and 46. But the priority for the Shermans was for Europe and with D-Day the demand for new tanks in Europe was too high to allow even a few hundred to be sent to Australia. So the Australian Army went without new tanks and had to keep using the Matilda up to the end of the war and scrabble to try and get a handful of (paid for in Sterling) Churchills from the UK. New production ACIIIs and IVs would hugely improved the combat power of the Australian units in those final campaigns and should have saved some of the lives lost in finishing off the Japanese.
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Offline Basilisk

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Re: Sentinel ACIV
« Reply #48 on: October 01, 2015, 05:01:55 am »
Great pictures Basilisk, thanks for posting them. Especially the quad Gipsy Major engine. Very shiny and chrome.

...

You're welcome. I'd read about the Quad Gipsy engine in D. P. Mellor's account in The Role of Industry but had never seen much else about it. It was a bit surprising to see pictures of it, a little like finding a photo of some mythical beast. And it certainly looks very professional compared to its predecessors. The accompanying text doesn't say too much about it, 510hp at 2500rpm, best fuel economy 340hp at 2000rpm, and that it was developed in 1942 to guard against loss of supply of Cadillac engines, presumably because the US was now using them in the M3/M5 and M24 light tanks, which is slightly amusing as Cadillac apparently didn't think the Cloverleaf power pack for the Australian Cruiser could actually be made to work.


The Cloverleaf-Cadillac for the Sentinel. Well the whole power pack really, including radiators, fuel tanks, and the engine subframe ready to go into the back of the tank.


The er "bare" Perrier-Cadillac for the Thunderbolt and AC4.


Michael

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Re: Sentinel ACIV
« Reply #49 on: September 18, 2016, 06:36:17 pm »
Here's a very bad scan (not my fault) of a blue print of the planned AC3 production tank. Has quite  different turret shape to the AC1.

That's a very interesting drawing I've not seen before are there other views and can copies be obtained? I'm looking to build a Sentinel I, III & IV as soon as I can collect the information.

The torsion bar suspension looks remarkably like that trialled on the Sherman right down to the rear idler mounting arrangement


Offline Foo Fighter

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Re: Sentinel ACIV
« Reply #50 on: September 23, 2016, 05:14:55 am »
My problems with the Sentinel are based around the usability of the vehicle as a crewman.  I have seen a few video items, notably from WOT (yes poo poo that if you like) demonstrating the interior layout which would have resulted in reduced crew efficiency, possibly to the point of vulnerability, much like the T34-76 with its two man turret and paucity of radio's and a reliance on flags for communication between troop/platoon vehicles.  It is far easier to produce a reasonable vehicle, harder to make that vehicle work in combat situations.  How can you logically have a gunner in an afv sitting sideways on to the gunsight and his legs liable to crush injuries from the gun?





« Last Edit: September 23, 2016, 07:03:28 am by Foo Fighter »

Offline Abraham Gubler

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Re: Sentinel ACIV
« Reply #51 on: September 25, 2016, 06:23:48 pm »
My problems with the Sentinel are based around the usability of the vehicle as a crewman.  I have seen a few video items, notably from WOT (yes poo poo that if you like) demonstrating the interior layout which would have resulted in reduced crew efficiency, possibly to the point of vulnerability, much like the T34-76 with its two man turret and paucity of radio's and a reliance on flags for communication between troop/platoon vehicles.  It is far easier to produce a reasonable vehicle, harder to make that vehicle work in combat situations.  How can you logically have a gunner in an afv sitting sideways on to the gunsight and his legs liable to crush injuries from the gun?

Well I could only watch it up to the point where he admitted he wasn't an electrician but was still upset he couldn't understand the manual's chapter on the electrical traverse system. This guy seems to be the embodiment of the 'I know nothing, but I'll still complain' attitude that is pervasive in this 'hipster’ centric world. Just because you have an IQ one or two standard deviations above the norm doesn’t mean you can just use your intuition to work out everything from a knowledge poor base. You just make things worse!

For starters one needs to place the AC1 in context of 1940. Sure the rotating commander’s cupola only has two periscopes but considering the alternative was the “sun roof” on the Cruiser tanks of the time that isn’t so bad. Yes the turret is cramped but so was every other tank of that time. Try sitting in the turret of an ASLAV-25, you don’t exactly have much room to trim your beard and man bun. But unlike others like the T-34 it provides the crew with a rotating basket and electrical traverse to enable them to fight the tank in response to changing circumstances. So there is a stores box in the way of the gunner’s forward view port, move the box! Having a wide angle forward view for the gunner is fundamental to target acquisition. Tanks that provided the gunner with such forward vision in addition to the gun sight are far more lethal than those that just provide the later. And it did have a freaking radio so what’s the deal with the signal flags comment?

The ACI had a range of faults like the electrical turret traverse would only work when the tank was level to the horizon. But it had things that in 1940-42 would be much missed in other tanks that had to be used in combat. Like horizontal volute spring suspension (HVSS of M4A3E8 “East Eight” fame), under armour access to the engine bay and three power units for degraded operations and pretty importantly for a tank decent armour (resistant to the enemy’s basic anti-tank weapon). All of which would mean it could get into action instead of being left on the side of the road and survive being targeted. Something that couldn’t be said for the Crusiers, Covenanters, Crusaders and Stuarts being used by the Allies at this time.
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Offline Basilisk

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Re: Sentinel ACIV
« Reply #52 on: September 26, 2016, 03:16:53 am »
Well I could only watch it up to the point where he admitted he wasn't an electrician but was still upset he couldn't understand the manual's chapter on the electrical traverse system. This guy seems to be the embodiment of the 'I know nothing, but I'll still complain' attitude that is pervasive in this 'hipster’ centric world. Just because you have an IQ one or two standard deviations above the norm doesn’t mean you can just use your intuition to work out everything from a knowledge poor base. You just make things worse!
The odd part is that the manual isn't that hard to understand, I'm not an electrician either so there are a few features which I can only make an educated guess at why they were done in a particular way, but I understand the basics of it. There are two motors only, one drives the turret around, the other is there purely to provide high frequency switching to the first, the balance of off and on time being controlled by the position of a set of contact plates. That is it is an electro-mechanical pulse width modulation system. You'll find something very similar in almost any variable speed power tool today only now it's done with electronics.

I agree with you, there are so very many things wrong it those videos they are of limited usefulness. The bit he points to as the power traverse, is a secondary means of control meant to be used for fine control when tracking a moving target. The primary means is the manual traverse crank which can also be used to operate the power traverse system. You can even see the cover that shields the chain drive linking the crank to the traverse controller in the video. This is why the traverse controller is located where it is, not to torment the gunner when using the wheel but so he doesn’t have to use the wheel because his left hand can stay on the crank.

I did get a chuckle when he said the external fuel tank isn't connected to the internal tank, when even as he says this you can see what appears to be the perished remains of a rubber hose going through the engine cover to connect to the internal fuel tank.

The ACI had a range of faults like the electrical turret traverse would only work when the tank was level to the horizon.
Not completely true, during testing the tank's traverse didn't work very well beyond about 16 degrees however it was also apparent that there was something wrong with that particular tank. They got a second tank and it worked just fine at an angle of 30 degrees. The problem with the first one I believe was traced back to spacers installed to raise the turret ring something like 1/16 or 1/8 of an inch, the spacers had been made to fit around the studs not by having a hole punched in them but by having a slot cut instead, this had allowed the the spacers to move a little bit and star rubbing on the moving parts. This additional resistance along with the fact that the Sentinel turret is back heavy to begin with tripped the current limiting relay to stop the circuit burning out.

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Re: Sentinel ACIV
« Reply #53 on: September 26, 2016, 03:52:50 am »
As a tank gunner myself, out of the army but I still know how things work, or not.  Powered traverse is not the fine adjustment tool, manual control is much finer.  Also, you need to see the interior to see just how bad the vehicle would be to operate.  That thing would be a liability in ANY action involving opposing tank formations.  As a qualified tank crewman and commander I have the insight to state this from knowledge rather than not liking the beginning of a video tour of a vehicle (tank).

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Re: Sentinel ACIV
« Reply #54 on: September 26, 2016, 06:05:00 am »
Powered traverse is not the fine adjustment tool, manual control is much finer.
I never said it was, I said what was pointed to in the video was intended for finer control of the the input of the powered traverse system when using the powered traverse to track a moving target. The description of its purpose and operation is quite precise. The video is simply wrong on this matter (and many others beside) and no amount of experience you may have had on other vehicles changes that.

If the Chieftain chooses to ride side saddle in the gunner's seat, in spite of all the problems this causes, then that is his business. That a 2M tall Irish tanker doesn’t fit very well into the Sentinel gunner's position isn't a huge surprise, that he didn't twig that the bellows looking thing on the seat support almost certainly means it is adjustable and can therefore be lowered so he can sit facing near forwards like you are clearly supposed to perhaps is.

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Re: Sentinel ACIV
« Reply #55 on: September 26, 2016, 06:40:23 am »
Not really but then I sometimes wonder what the point of having this designed was in the first place and a point to Mr Gubler, the signal flags point was about the T34-76 and how with different problems the vehicles were going to be of limited use in action.

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Re: Sentinel ACIV
« Reply #56 on: September 26, 2016, 11:30:36 pm »
Here's a very bad scan (not my fault) of a blue print of the planned AC3 production tank. Has quite  different turret shape to the AC1.

That's a very interesting drawing I've not seen before are there other views and can copies be obtained? I'm looking to build a Sentinel I, III & IV as soon as I can collect the information.

The torsion bar suspension looks remarkably like that trialled on the Sherman right down to the rear idler mounting arrangement



Sorry just noticed this post. If I had more imagery I would post it here for sure. There is no doubt a lot more data on the AC program in the ANAO files in Melbourne. But I'm 1,000 miles away and I'm no Proclaimer.
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Offline Abraham Gubler

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Re: Sentinel ACIV
« Reply #57 on: September 26, 2016, 11:45:10 pm »
Quote from: Basilisk link=topic=8514.msg290729#msg290729
I agree with you, there are so very many things wrong it those videos they are of limited usefulness.

I did get a chuckle when he said the external fuel tank isn't connected to the internal tank, when even as he says this you can see what appears to be the perished remains of a rubber hose going through the engine cover to connect to the internal fuel tank.

I can't say I watched all of the vid just the start of part 1 and part 2 up until the electrics comment. I was turned off immediately by the smug rejection of what he labeled as a 'chute' on the turret top that went to a port below the turret. He couldn't understand what it was for based on his intuition so rejected it immediately. The worst of post modern anti expertise. He never asked why would such a useless feature be fitted therefore it must be something else. Just assumed the Australian tank engineers wanted an under armour chute from the outside top of the turret to the outside top of the hull. And were therefore complete idiots deserving of his scorn.

It was pretty clear to me that this chute is most likely an air vent for the turret. Fresh cool air in the bottom and hot fumy air out the top. With, most likely, a hard to see from outside vent in the interior side of the chute. It even has a freakin grill over the top of it. Like every air vent everywhere.

Quote
Not completely true, during testing the tank's traverse didn't work very well beyond about 16 degrees however it was also apparent that there was something wrong with that particular tank. They got a second tank and it worked just fine at an angle of 30 degrees.

Hoisted by own petard. Here I am complaining about someone elses ignorant compaints and I do the same from some half remembered factoid. My apologies.
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Offline Abraham Gubler

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Re: Sentinel ACIV
« Reply #58 on: September 26, 2016, 11:56:19 pm »
As a tank gunner myself, out of the army but I still know how things work, or not.  Powered traverse is not the fine adjustment tool, manual control is much finer.  Also, you need to see the interior to see just how bad the vehicle would be to operate.  That thing would be a liability in ANY action involving opposing tank formations.  As a qualified tank crewman and commander I have the insight to state this from knowledge rather than not liking the beginning of a video tour of a vehicle (tank).

Of course you must be out of Army if you were a tank gunner circa 1940. You must be well into your 90s by now so congratulations on your ling life and thankyou for your service, assuming you fought on the Allied side in WWII.

If by chance your military service was of a more recent vintage then I suggest it has no relevance here. Tank design has come a long way since 1940 and with it the all important human machine interface.

The ACI was an improvement in HMI over it's contemporaries. Have a look inside the turrets of the Crusader (has no commander's hatch), the Valentine (has no commander) and the Comet (1945 and still no room for the gunner to dance a jig) before judging this beast. And as soon as product improvement was available the AC program increased the turret ring in the ACIII and then again for the ACIV allowing for much improved HMI as well as bigger guns. No such luck for the Cromwell and Churchill.
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Offline Foo Fighter

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Re: Sentinel ACIV
« Reply #59 on: September 27, 2016, 04:22:39 am »
I understand your opinions and thought vis a vis my experience.  I did not serve in WWII, however, my experience in armoured vehicles of various types allows me to better understand their use and usability above that of someone who has no experience.  The gunners seat back for example, is what suggests the gunner sat sideways, as did the commander and these points reduce efficiency of the crew.  I am not stating that the other vehicles you mention are good either, I am well aware that there were many tanks and self propelled guns etc that were totally useless let alone not fit for purpose.  For example, the Chieftain tank was fitted with a BL L60 powerpack which was a nightmare.  The fanbelts were very well made and with little effort. tore out the fans from the housings and ripped open the radiators.  Lots of 29 gallon yellow smokescreens told the bratwurst sellers exactly where lots of our crews could be found.  Do you think the east Germans/Russians would have any trouble finding us too?  Solution?  Drill holes in the fanbelts so the fanbelts simply break up and, you guessed it, made holes in the radiators.  Sharp joined up thinking there.  For those who like the ac sentinel I merely say this, my opinions are exactly that and nothing more just think on what has been said and think about whether YOU would like to go into action in one of those before you shoot down the opinions of others.

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Re: Sentinel ACIV
« Reply #60 on: September 27, 2016, 04:36:59 am »
The gunners seat back for example, is what suggests the gunner sat sideways...
But the Sentinel's gunner's seat doesn't have a back.

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Re: Sentinel ACIV
« Reply #61 on: September 27, 2016, 09:49:24 am »
I thought I saw one in the video but  I know some people in the Bovington tank museum so I'll get back to you on that.  Still not a good tank in any event.

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Re: Sentinel ACIV
« Reply #62 on: September 27, 2016, 07:59:14 pm »
I understand your opinions and thought vis a vis my experience.  I did not serve in WWII, however, my experience in armoured vehicles of various types allows me to better understand their use and usability above that of someone who has no experience.  The gunners seat back for example, is what suggests the gunner sat sideways, as did the commander and these points reduce efficiency of the crew.  I am not stating that the other vehicles you mention are good either, I am well aware that there were many tanks and self propelled guns etc that were totally useless let alone not fit for purpose.  For example, the Chieftain tank was fitted with a BL L60 powerpack which was a nightmare.  The fanbelts were very well made and with little effort. tore out the fans from the housings and ripped open the radiators.  Lots of 29 gallon yellow smokescreens told the bratwurst sellers exactly where lots of our crews could be found.  Do you think the east Germans/Russians would have any trouble finding us too?  Solution?  Drill holes in the fanbelts so the fanbelts simply break up and, you guessed it, made holes in the radiators.  Sharp joined up thinking there.  For those who like the ac sentinel I merely say this, my opinions are exactly that and nothing more just think on what has been said and think about whether YOU would like to go into action in one of those before you shoot down the opinions of others.

I think you have some valid points but I am not sure about your criticisms of either the L60 or the Sentinel.  Everything should not be viewed through a lens of hindsight.  It should be looked at what was known at the time.  The L60 had it's problems early on, without a doubt but then so do all new designs.   Could it have been made better?  Without a doubt but there was a learning process and by the end of the Chieftain, the L60 was considered a reliable and useful tank engine. 

Same for the Sentinel.  The Sentinel I was as the narrator points out, the first tank ever produced Downunder.   They had few others to compare it to and so it had it's problems.  That he was also looking at an early example which was over 60 years old, also meant that all he had to work things out were the manuals it was supplied with, rather than the institutional knowledge that was available at the time.  I don't doubt they got quite a few things wrong and did them very differently to an M1 Abram MBT of today.  However, the Sentinel far from being a "bad" tank was actually in many ways quite admirable, as Chieftain himself points out.  It was the first cast hull tank, it was well armoured, and at least initially, adequately armed.   Its powerpack while complex worked and moved the vehicle.   Its crew was obviously meant to be smaller men than Chieftains 2 metre frame.  That their controls and seating was awkward was  unfortunate but then, ergonomics hadn't been invented yet.   That the Sentinel contributed directly to the Sherman Firefly's mounting of a 17 Pdr gun shouldn't be overlooked, nor that the Sentinel was uparmed twice, going from 2 Pdr to 25 Pdr to 17 Pdr in it's life shouldn't be without consideration either IMO.

Offline Abraham Gubler

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Re: Sentinel ACIV
« Reply #63 on: September 27, 2016, 11:56:39 pm »
The gunners seat back for example, is what suggests the gunner sat sideways, as did the commander and these points reduce efficiency of the crew.  I am not stating that the other vehicles you mention are good either, I am well aware that there were many tanks and self propelled guns etc that were totally useless let alone not fit for purpose.

This is a good point to make and such an arrangement would be foolish but I don’t think you can make that conculsion based on the evidence of how the seats are attached to the turret basket. By the way there are some artillery pieces with a right angle sighting system for the gunner but this is clearly not the way the ACI is laid out.

What determines the orientation of the crew is their controls and sighting axis. The ACI like contemporary Cruiser and Infantry tanks armed with a 2 Pounder gun have axial gunsights parallel to the bore of the weapon. The control panel (if you can call it that) is also located perpendicular to the weapon’s bore. As can be seen in the pictures I uploaded above the gunner’s position is wedged in between the turret ring and the gun mounting creating a small triangular space. But the gunner has to orientate their body (or at least their upper body) parallel to the gun’s bore. At worst they may have to angle their hips inwards towards the centre axis of the turret but their torso, arms and head are all going to be aligned parallel to this axis. Kind of like how we used to be taught to shoot a rifle with the hips angled away from the line of fire. That is until modern body armour made it far safer to have the striking face perpendicular to incoming fire rather than reducing the width of your body as a target and having incoming fire strike your kidneys and then pass on energy through their entire side to side distance of your torso.

For example, the Chieftain tank was fitted with a BL L60 powerpack which was a nightmare.  The fanbelts were very well made and with little effort. tore out the fans from the housings and ripped open the radiators.  Lots of 29 gallon yellow smokescreens told the bratwurst sellers exactly where lots of our crews could be found.  Do you think the east Germans/Russians would have any trouble finding us too?  Solution?  Drill holes in the fanbelts so the fanbelts simply break up and, you guessed it, made holes in the radiators.  Sharp joined up thinking there.

If it is any consolation the T-64 also used the same engine configuration. Two stroke opposed pistons are inherently smoky (even when the radiators haven’t been destroyed by a fleeing fan). Sleeve valve engines on both sides of WWIII would surround both the Chieftain and the T-64 with clouds of white smoke.
"There is a tendency in our planning to confuse the unfamiliar with the improbable." Thomas Schelling

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Re: Sentinel ACIV
« Reply #64 on: September 28, 2016, 12:34:03 am »
It was pretty clear to me that this chute is most likely an air vent for the turret. Fresh cool air in the bottom and hot fumy air out the top. With, most likely, a hard to see from outside vent in the interior side of the chute. It even has a freakin grill over the top of it. Like every air vent everywhere.
You are right, it is just a vent. Puckapunyal let me crawl around inside theirs to my hearts content. Purely guesswork on my part but the turret rood slopes down away from the commander's cupola so there is nothing to obstruct his view. So presumably a mushroom type vent would be in the way so something internal had to be done. There is a requirement that the tank be protected from burning material, I think it said thermite, hence no air vents in the top of the hull of tank anywhere. To divert anything that enters through the vents or falls into the vent in the roof of the turret there is a sort of three sided tray baffle plate that connects the top and bottom vents but it is not welded to the sides so air can be drawn into the turret by the draft created by the radiator fan when the engine is running. The air vents in the rear corners of the turret also have additional baffle plates welded in to stop bullets and fragments from getting into the turret.

Hoisted by own petard. Here I am complaining about someone elses ignorant compaints and I do the same from some half remembered factoid. My apologies.
Not your fault mate, it is in a few books, presumably copied from the first, and has become 'fact'. The trouble is that it is kind of correct in that in testing the traverse system didn't work past a certain angle, it is probably misleading though.

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Re: Sentinel ACIV
« Reply #65 on: September 28, 2016, 12:36:21 am »
I thought I saw one in the video but  I know some people in the Bovington tank museum so I'll get back to you on that.  Still not a good tank in any event.
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Offline Foo Fighter

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Re: Sentinel ACIV
« Reply #66 on: September 28, 2016, 04:00:20 am »
I concede that, while the gunners seat is slewed it is nowhere near 90 degrees.  When I talk about assessing the value of a tank it is from a usability/tactical awareness angle.  The early T34 (The 76) having a two man turret had an unacceptable work rate for the commander/gunner.  I have seen interviews of crewmen of these vehicles and in particular at Kursk, the orders were not to be picky about tactics but to ram the German tanks.

The quality of armour is of secondary importance if your enemy can very simply flank you and destroy you from that flank at closer ranger.  Micheal Wittman was probably killed by a standard 75mm armed Sherman, from the flank and at what was probably under 100 yards rather than the Firefly armed Sherman which would have had to fire at about 2,000 yards, somewhat about its effective range.  When the first T34 and KV 1 tanks ran amok in the German lines they were destroyed by the same flanking moves or by the 88mm Flak.  If the Sentinel had been flanked it had little in the way of vision to react quickly enough and yes, I concede that it is by no means the only vehicle to suffer this problem.  The point of usability also, while paid little heed at the time, also effects whether you live or die when in contact with even inferior opposition.

As a point of note I would suggest the first really good tank we Brits produced was the Centurion and even then it was burdened with a rather pointless 20mm Polsten gun, increasing the work load of the loader for no good return.  The military and political high ups were so pathetic that even when they had several in the region of contact, they chose NOT to deploy them.

Offline Abraham Gubler

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Re: Sentinel ACIV
« Reply #67 on: September 28, 2016, 04:24:04 am »
The quality of armour is of secondary importance if your enemy can very simply flank you and destroy you from that flank at closer ranger.

Absolutely. An American statistical analysis of WWII and Korean tank battles showed that the side that detected the enemy first won the subsequent engagement 90% of the time. Irrespective of what kind of tank they were using or how many they had. Such situational awareness superiority is more important than other ‘traditional’ tactical factors (armour, firepower, mobility). And clearly demonstrated by the German armoured force in WWII until everyone else caught on. Despite having tanks that were often inferior in traditional quality metrics (armour, firepower, mobility) and numbers they won battle after battle because they had tanks with far better communications, target acquisition, etc and were trained to leverage these advantage.
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Offline Abraham Gubler

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Re: Sentinel ACIV
« Reply #68 on: September 28, 2016, 04:26:08 am »
You are right, it is just a vent.

Thanks now I can brag about that for ages...
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Offline Kadija_Man

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Re: Sentinel ACIV
« Reply #69 on: September 28, 2016, 06:23:47 am »
The military and political high ups were so pathetic that even when they had several in the region of contact, they chose NOT to deploy them.

Really?  And I've always understood the first Centurion Mk.Is which reached NW Europe did so just after the end of hostilities...

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Re: Sentinel ACIV
« Reply #70 on: September 28, 2016, 06:26:09 am »
As a point of note I would suggest the first really good tank we Brits produced was the Centurion and even then it was burdened with a rather pointless 20mm Polsten gun, increasing the work load of the loader for no good return.

So, the Churchill was of no value?  Interesting.  It was considered the best of the British tanks in 1944-45 by most who understood it's value...

Offline Foo Fighter

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Re: Sentinel ACIV
« Reply #71 on: September 28, 2016, 01:07:22 pm »
Have you read what I have written?  Like the early T-34, the first Churchill was not exactly great being too slow and without a gun worthy of the name.  I have read memoirs of tankers who crewed Churchill tanks and they dreaded tank on tank engagements.  Churchill was borne out of the WWI theory of tank design namely slow plodding infantry tanks and faster cruisers.  Can you honestly say that Churchill was fit to be pitted against later MK IV or especially the MK V?

Offline Kadija_Man

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Re: Sentinel ACIV
« Reply #72 on: September 29, 2016, 10:24:39 pm »
As I said, before it was deleted. the Churchill in it's later marks was virtually invulnerable to 88mm fire - the only active Allied tank in 1944-45 that was.   It was reliable and it had the best gearbox available to any AFV in WWII - being able to climb slopes other AFVs would baulk at as was shown in Tunisia and Italy.   What it lacked at least initially was a good HE capable gun.  That was fixed by initially taking 75mm guns from Shermans which had been knocked out and then through the Britishs' own 75mm gun (based on the 6 Pdr, rebored).  The Churchill was of course, an Infantry Tank and was never intended to take on enemy Panzers.   It performed admirably in the advance across NW Europe, into Germany.  It was also perhaps the most adaptable and adapted AFV the Western Allies had, forming the core of the specialist 79 Armoured Division.

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Re: Sentinel ACIV
« Reply #73 on: September 29, 2016, 11:13:18 pm »
Let me try to sum up: The Churchill, designed to the British ideas of an "Infantry tank", was good for this task,
but had drawbacks, at least in its early marks, in tank-vs-tank confrontations.

And now, may I remind you, that the title of this thread is "Sentinel ACIV" ?  ;)
It takes a long time, before all mistakes are made ...

Offline Abraham Gubler

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Re: Sentinel ACIV
« Reply #74 on: January 19, 2018, 07:44:59 pm »
Sorry for the long absence in posting but I’ve been very busy with un-secret projects made of real steel and the like of late. I’m currently on holiday in Melbourne until next week when I return to defence projects (real world). So being in this town and one of these guys/gals (member of secretprojects.co.uk) I had to visit the National Archive while here and look up their files on the Australian Cruiser Tank program’s AC1, AC2, AC3 and AC4 (no reference to anything called a Whatsinel).

The results were great and I thought to share a samplerer for you all in the ASAP. More to come as well as CA-15 and CA-23 for the zoom zooms.
"There is a tendency in our planning to confuse the unfamiliar with the improbable." Thomas Schelling

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Re: Sentinel ACIV
« Reply #75 on: January 20, 2018, 11:14:08 am »
The results were great and I thought to share a samplerer for you all in the ASAP. More to come as well as CA-15 and CA-23 for the zoom zooms.

Looking forward to more mate.

Offline Abraham Gubler

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Re: Sentinel ACIV
« Reply #76 on: January 24, 2018, 02:40:00 am »
Here a handful of AC1 pictures from the archive. The caption (actually a hand typed, half sized, tissue paper sheet inserted before the photo) of the AC1 bogged in the dried up river bed assures the reader that the tank was able to recover from this position under its own power.

In my previous post hawkeyes may have noticed the photo of nine cast hulls of Australian Cruiser Tanks stacked three up? Eight of these are AC3 hulls with a single AC1 in mid right. These hulls have been cast, heat treated and machined were needed and are ready for transport to the production line. 200 AC3s were ordered and there is an extensive folio in the National Archives of all the purchase orders that went out for all the sub-components. Then attached to each one is a 1943 dated stop work order.
"There is a tendency in our planning to confuse the unfamiliar with the improbable." Thomas Schelling

Offline Basilisk

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Re: Sentinel ACIV
« Reply #77 on: January 24, 2018, 07:26:48 am »
That's quite neat, I haven't seen some of these before. Thanks for sharing.

In my previous post hawkeyes may have noticed the photo of nine cast hulls of Australian Cruiser Tanks stacked three up? Eight of these are AC3 hulls with a single AC1 in mid right.
Looks like 8 AC3 hulls, 2 AC1 Hulls, at least 1 and probably 3 AC3 axle housings, and right at the bottom of the photo what looks to me like the top of an AC1 turret.

Offline Abraham Gubler

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Re: Sentinel ACIV
« Reply #78 on: January 25, 2018, 07:37:25 pm »
The photos are from a great ‘book’ called “The Production of Armoured Fighting Vehicles in Australia” put together by the AFVs Directorate in early 1943 as a record of what they had done to date with the AC Tank program. It’s a huge leather bound thing held together by three bolts full of photo plates and information about the design and production of the tanks.
"There is a tendency in our planning to confuse the unfamiliar with the improbable." Thomas Schelling

Offline Abraham Gubler

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Re: Sentinel ACIV
« Reply #79 on: January 28, 2018, 02:30:06 am »
Some more imagery.
"There is a tendency in our planning to confuse the unfamiliar with the improbable." Thomas Schelling

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Re: Sentinel ACIV
« Reply #80 on: January 28, 2018, 05:28:47 am »
The photos are from a great ‘book’ called “The Production of Armoured Fighting Vehicles in Australia” put together by the AFVs Directorate in early 1943 as a record of what they had done to date with the AC Tank program. It’s a huge leather bound thing held together by three bolts full of photo plates and information about the design and production of the tanks.

Ah, that makes sense, David Fletcher wrote an article in Classic Military Vehicles I think that used that book as a source, so I guess a copy went along with the Sentinel that went to Bovington.

Offline Abraham Gubler

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Re: Sentinel ACIV
« Reply #81 on: January 30, 2018, 02:10:58 am »
Some more pics.

Top to Bottom: AC3 wooden mockup, previously published AC3 prototype using AC1 hull, AC3 cast hull ready for assembly, AC3 vs Panzer IV, AC3 vs Panzer III
"There is a tendency in our planning to confuse the unfamiliar with the improbable." Thomas Schelling

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Offline rdmr

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Re: Sentinel ACIV
« Reply #84 on: November 25, 2018, 05:09:11 pm »
Fantastic ninjrk!

Offline Basilisk

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Re: Sentinel ACIV
« Reply #85 on: November 25, 2018, 09:08:20 pm »
100+ pages of plans for the AC3 here: https://recordsearch.naa.gov.au/SearchNRetrieve/Gallery151/dist/JGalleryViewer.aspx?B=382893&S=15&N=103&R=0#/SearchNRetrieve/NAAMedia/ShowImage.aspx?B=382893&T=P&S=1

From memory, if you have a look somewhere around half way through that is a couple of drawings of an AC4 hull. It only has a 64" turret ring so must be an early draft before the design was enlarged to 70".

I've never figured out why certain files get digitised before others that one was scanned something like 18 months ago, they don't seem to be going by age, or by series, or anything else obvious. Tangentially related to this thread since the AC4 could also carry a 25 pounder, these are from a couple of months back, the first experiment towards a 25 pdr tank gun, tested June 1942:

Barcode: 33033164


Barcode: 33033162


The rest are AC1 but you can find them under series MP891/30.

Offline ninjrk

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Re: Sentinel ACIV
« Reply #86 on: December 03, 2018, 06:09:08 am »
I confess I'm a little surprised that there was no mention of trying to fit the QEF 75mm main gun in the Sentinel instead of the 25 pdr.  I'd assume its because the 25 pdr was in production in Australia and ammunition was plentiful?

Offline Basilisk

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Re: Sentinel ACIV
« Reply #87 on: December 03, 2018, 06:57:23 am »
Pretty much. The intent was to only to use imported components where there was no local alternative. Sometimes you see comments online suggesting the Vickers was a bit old fashioned or too bulky, and they should have used the BESA, well neither the BESA nor its ammunition were being made in Australia. I think there is a fairly short list somewhere of foreign components required for the tanks, the major ones were the engines and roller element bearings, and bunch of little things like light bulbs.

Having said that, as designs were drawn up to fit a 6 pdr to the Sentinel, and as I understand it the OQF 75mm is essentially a rebarreled 6 pdr, I don't imagine it would have been out of the realm of possibility to make a 75mm Sentinel.

Offline rdmr

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Re: Sentinel ACIV
« Reply #88 on: December 06, 2018, 02:48:52 pm »
And I think the engines, although technically made overseas, were chosen as there was a large stock in country ( I do not know where it was, or who owned it ) and presented no or very little issue with supply.

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Re: Sentinel ACIV
« Reply #89 on: December 07, 2018, 12:59:12 am »
And I think the engines, although technically made overseas, were chosen as there was a large stock in country ( I do not know where it was, or who owned it ) and presented no or very little issue with supply.

No, the Cadillac V8s came direct from the US. As they weren't anybody's first choice as a tank engine, the Americans and even the manufacturer didn't think a multiple engine power plant would work, there was no competing demand and they could be had in almost any quantity desired. Until the US started putting multiple Cadillac V8s into their tanks.

There was I believe a stock of Ford V8s in Australia, they were used in the LP Carriers. A triple Ford V8 using those was one of the fall backs if the Cadillacs couldn't be had.