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Author Topic: Sentinel ACIV  (Read 31240 times)

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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Pioneer   

   
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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.
"There is a tendency in our planning to confuse the unfamiliar with the improbable." Thomas Schelling

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.