Abraham Gubler

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During WWII the British Army came up with the idea of an Assault Tank to defeat German emplaced anti tank guns (PAK) via artillery suppression. Trialled with Churchills the idea was that the assault tank unit would advance into a friendly artillery bombardment that would suppress the anti tank gun crews. While the anti tank crews were in their bunkers and trenches the assault tanks would drive around inside the bombardment and destroy all the unmanned anti tank guns. The trials were considered a success with the tanks being able to easily identify targets within the bombardment. The only problem was minor damage caused by the artillery splinters caused a few mobility kills (damaging tracks) and air bursts couldn’t be used due to the weakness of the engine bay roof armour. So new designs were prepared for assault tanks that were immune to low and medium intensity bombardments.

To provide the assault tank capability English Electric were contracted to develop the A33 “Excelsior” and in the US American Locomotive the T14 (to a British specification). Prototypes of both tanks were built but neither entered mass production. Further developments focused on a light assault tank (A38 Valiant) and heavy tanks with massive gun armament.
 

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Grey Havoc

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T14 first test report and some other project related documentation: http://www.dtic.mil/dtic/tr/fulltext/u2/b965290.pdf
 

Avimimus

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That is a pretty neat design (duel treads and increased roof armour). It is interesting to see that these features weren't carried on post-war (as mobility kill weapons and air attacks became more common).

Any idea what the thickness of the roof armour is? I'm thinking about fusing problems leading to direct hits from the airburst shells.

It also sounds rather hellish to be inside.
 

JohnR

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I've often wondered if the T14 had entered service early enough, if it could have been upgraded to a "Firefly" variant with a 17pdr or 77mm HV. If so how would it have stood up against a Tiger or Panther?
 

A Tentative Fleet Plan

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A-29 Clan assault tank designed by Rolls-Royce.

From the attached Article:
In late November/early December 1941, the British General Staff issued specifications for an ‘Assault’ tank and allocated the General Staff number A29 and was handed over to Rolls-Royce to design while Birmingham Carriage & Wagon Company was allocated the General Staff number A30.

Rolls-Royce, although not as renown as Nuffield (Crusader) or Vauxhall (Churchill) was no stranger to tank design. Other than developing the Meteor engine, which powered many British tank designs, Rolls-Royce’s Clan Foundry in Belper also was involved in the redesign of the Cromwell Mark III tank. Clan Foundry used this experience to concieve the A29, which they had christened as ‘Clan’ after the foundry, where it was made.

The tank, developed by Rolls-Royce – although based on the Cromwell – was a behemoth, at 9’ 7” tall (2.92 m) and an estimated 43 long tons 5cwts (50.65 tons), of which 16 long tons was armour (the side by side sketch for the A29 and A30 are to two different scales). The front of both the hull and turret were 5” (127 mm) thick, and the side hull, including armour skirt, was 3½” (88.9 mm) thick. Like its rival design, the Challenger, it also was armed with a 76,2 mm QF 17-pounder gun, mounted in a turret similar to (but not exactly the same as) the one of Challenger (once again, it is worth noting the difference in scale of the two drawings). Although it is not mentioned in the written material, it is safe to assume that the Clan would invariably have an internal mantlet, adding to the frontal turret’s overall thickness like other contemporary British mantletess tanks.

The A29 Clan was to be propelled by a Rolls-Royce Meteor engine, up-rated to 700 bhp, which would give the Clan a top speed of 30 mph (48.3 kph) and power to weight ratio of 13.82 hp/tons. All this added armour and a heavier gun and turret of course came at cost, the weight was far higher than the existing Cromwell suspension could bear. Rolls-Royce’s solution was a new separate twin track suspension design, each track was 11” (279.4 mm) thick for a total of 22” wide tracks (558.8 mm), which would give the Clan excellent terrain passability. Inevitably, issues arose with the new, complicated suspension system, which caused delays in the programme, pushing the expected development finish all the way past February 1943. This proved to be the A29 Clan’s undoing and the project was cancelled in favour of the simpler A30 Challenger design. Rolls-Royce attempted to address these suspension issues with yet another design, the A31, but it too was cancelled.

A29 Clan

Weight: 50.65 tons
Height: 2.92 mOA Length: 7.47 mWidth: 3.2 m
Contact Length: 5.58 m
Clearance: 0.5 m

Engine: Rolls-Royce Meteor V-12 700 bhp, petrol, 13.82 hp/tons
Top Speed: 48.3 kph
Tracks: 279.4 m x2 (558.8 mm)

Armament: 1 QF 17-pounder (171/239/38mm), 1 unspecified coaxial machine gun

Armour: 127/88.9/???

Citation:

The Rolls-Royce Meteor: Cromwell and other applications by Evans, McWilliams, Whitworth and Birch
WO 291/1439 British tank data
7CXlTOL.jpg
qCateyL.jpg
 

tom!

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Hi.

The japanese army had a similar idea but for breaking through enemy artillery bombarddments. Result was the 140 t Superheavy Tank O-I which never went through the innitial test phase. It was a multi-turret design with a Type 96 15 cm howitzer in the main turret, a Type 1 47 mm QF gun in each of the 2 bow turrets plus a Type 97 7,7 mm MG in a rear turret.

This tank had a maximum armor of 15 cm and should be able to defeat direct hits of russian artillery rounds up to 122 mm caliber. The first tests showed that the design was more or less a failure due to the too high ground preasure. The tank almost immediately sank into softer ground up to the springs after driving onto it.

jap%20O-I%20seite%20schnitt%20skizze.jpg


jap%20O-I%20Panzerungsschema.jpg


Yours

tom! ;)
 

Iron Felix

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Soviet concepts of assault tanks:
1933 - 400-600 ton multiple turret tank, protected from 150 mm guns (200 mm armour, or more), one 152 or 203 mm cannon, two 45 or 76.2 mm guns, no less 30 kmph.
Projected 500-ton tank with 2x107, 2x76.2 and 2x45 mm guns, 4-12 7.62 mm DT machine guns, three flametrowers, one mortar.
1940 - no more 100 ton, protection from German 88 mm guns, caliber of cannon - 122 mm or more, no less 30 kmph.
Projected 75-ton "IS" ("Iosif Stalin"), main armour 110 mm, 122 mm A-19, or 130 mm B-13, or 152 mm ML-20 gun and four machine guns, 1100-1200 HP V-24 24-cylinder diesel engine, based on two V-2 12-cylinder diesel engines, or, 1000 HP MN-1 engine, or, 850 HP V-2 with turbocharger, to 35 kmph. Loading system of main gun - automatic bolt of gun, "tray", ramrod, automatic fume extractor, 50 rounds in big turret.
1942 - no more 100 ton, protection from German 105 mm guns
Projected "IS", armour 120-150 mm, "best gun for this tank - 152 mm Br-2, but, it's very heavy variant - weight of non-separable part no less 100 ton", full weight with other guns (A-19, B-13, ML-20) no more 100 ton, weight of non-separable part no more 60 ton. Two V-2 engines, full power 1200-1500 (?) HP (I heard about 750 HP version of V-2 with charger), 24 kmph.
Speed limits is very strange. Take a look at the difference:
IS-7 (1944-1949) - 68 ton, 1050 HP, 15.44 HP/ton, 56.7 kmph,
IS (1940) - 75 ton, 1100-1200 HP (potential two turbocharged V-2, 2x850 HP, 1900 HP), 14.67-16 (25.33) HP/ton, 30 kmph,
IS (1942) - 100 ton, 1200-1500 HP (1900 HP), 12-15 (19) HP/ton, 24 kmph.
I understand that the IS-7 had a more advanced transmission, but I think the real possible speed should be at least 40 kmph for the IS-1942 and at least 45 kmph for the IS-1940.
 
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JohnR

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Without wishing to hijack the thread, as I have already mentioned to the 17pdr and 77mm HV I was wondering if there were any proposals to fit the 77mm HV to the Sherman? Would it have been any easier to fit into the turret given its smaller breech block?
 

EwenS

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I’ve not read of any such plans. But I think there are a number of factors that would indicate it was unlikely.

Firstly, by the third quarter of 1944 when the 77mm HV armed Comet started to roll off the production line, there were difficulties securing enough 75mm Shermans to convert to Fireflies. So why would you undertake a project if you couldn’t get the base vehicle?

The alternative would have been to base the conversion on the second generation 76mm tanks, but that means starting the design from scratch again because of the different turret. Performance of the 77mm HV lies somewhere between the US 76mm and the 17pdr and the British do not seem to have been particularly enamoured with the former. Even though they took 1,330 M4A1 (76mm) in 1944 they were only issued to a few units.

Designing the 77mmHV didn’t mean the British had given up on the 17pdr. From May 1944 work proceeded on the detailed design of the Centurion, with 17pdr armed prototypes being produced for field testing by April 1945.
 

SleeperService2

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Taking the T-14 at Bovvie as a prototype and using the development applied to other US tanks then IMHO the following could have happened;
  1. The hull machine gun mount replaced by a similar one to the Sherman to eliminate the shot trap. Possibly using the Ford welded type to avoid conflict with US Army requirements for the cast item on the Sherman
  2. Earlier adoption of the E8 HVSS suspension on both Sherman and T-14 types to improve mobility
  3. The 76mm Sherman turret with twin circular hatches to replace the 75mm gun tanks possibly with a .50cal co-ax mg as fitted to Jumbos and others. 75mm vehicles to be retained as CS vehicles. This turret could be produced with the 17pdr as the main gun and maybe the commander and gunner on the LHS as British practice, the twin cupola arrangement would make this easier and offer better escape for the gunner
  4. As a separate development the Meteor engine could be designed in, possibly with a hull stretch similar to the M4A4. This would be welcomed by the US Army as the Ford engine was always in short supply. The extra power of the Meteor would bring mobility of the heavier T-14 close to the Sherman and be very close to the 'Universal tank'.
  5. Stretching a bit now but the CS tank could eventually mount the 25pdr as developed in Australia for the AC.3 in either a modified 76mm turret or a newly designed one

The result would be a single tank chassis from the US armed with British main guns and the Meteor engine. Both areas needing more logistic support than most. The .30 cal Browning could be replaced by the .303 version as already used in aircraft for further streamlining. With the heavy stuff being done in the US and the fitting out in UK factories the burden on UK industry would be reduced and output dramatically increased. The resulting vehicle would have stretch potential and would still allow extra resources to be allocated to the Centurion and the 20pdr gun. At the same time the UK tank builders could be re-organised to use modern methods; welded hulls, manufacturing components to tight tolerances, building by blocks all to an identical fit, and moving machine tools to a common family of footprint to make upgrading easier. All this did happen but the US had the knowledge in 1943 and the UK wasn't able to adapt to it for many, many years. That is another topic though....
 

Iron Felix

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I. S. Skitsyuk, November 18th, 1943, "Invulnerable tank"
image_4e6afb316da98.jpg
Amour (by proportions), turret - 250 mm, hull front (top) 250 + ~200 mm, hull front (bottom) 250 mm, side (top) more 250 mm, side (bottom) ~100-150 mm (+50-100 mm ?), rear ~60-80 mm. Lenght 6 m, beam 4 m, height 2 m. I haven't data about weight, engine, speed, and about weapons, but, I think, by weight "Invulnerable tank" wasn't less a IS-2/IS-3. Diameter of gun ~150-200 mm, I think, it's a 100 or 122 or 130 mm gun.
Also, data about T-64 light tank project (1945) - turret frontal armour 220 mm, hull armour - front top 45 mm 8°, front bottom 200 mm, hull 150 mm, rear 75 mm. Weight 26 ton, main gun 85 mm ZIS-S-53. Also, planned two SPGs on T-64 base - 25 ton 100 mm AT SPG and 20 ton 122 mm howitzer.
 
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Iron Felix

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Five assault tank projects from "Stalin's supertanks, IS-7, etc. Superheavy tank of the USSR", Maxim Kolomiets:

February, 1942, VAMM RKKA - 70-75 ton, armour 100-150 mm, 107 mm main gun with DT machine gun, and two DT + one flamethrower in hull front, 5 crews, 600-750 HP V-2K engine, 30 kmph. I heard about "rational armour angles" for this tank from other book, I think, this tank looks like a big T-34.

June 26th, 1942, "TNT", "Tank novogo tipa" ("New Type Tank"), authors - Vdovenko and Kutov. Based on KV, two 76.2 mm guns in turret, "spherical armour", caterpillars are covered with armour.

December 3th, 1943, requirements for new heavy tank - weight 55 ton, armour - turret 160 mm, hull front 200 mm, side 160 mm, rear 120 mm, one 122 mm gun (I think, D-25 or other analogical gun) or 152 mm howitzer (I think, ML-20S), 5 crews, 800-1000 HP engine, 35 kmph.

Early 1945, requirements - protected from 88-128 mm guns with 1200 mps, 122 mm gun with 1000-1100 mps or 152 mm gun, 1000-1200 HP diesel engine, 60 kmph.

1945-1946, "Object 705" - 100 ton, 130 or 152 mm gun, three 14.5 and four 7.62 mm machine guns, 1800-2000 HP engine.
 

DiePanzerKanone

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This thread strayed very off-topic from British class of assault tank - so here are a list of them:

- Assault Tank T14
- A.33 Assault Tank "Commodore"
- Tortoise class of assault tanks from Nuffield, including A.T.1 to A.T.25 (A.T.16 is the A.39 Tortoise that we all know and love today)

the A.29 tank "Clan" mentioned earlier is a cruiser tank, not an assault tank
 

SleeperService2

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This thread strayed very off-topic from British class of assault tank - so here are a list of them:

- Assault Tank T14
- A.33 Assault Tank "Commodore"
- Tortoise class of assault tanks from Nuffield, including A.T.1 to A.T.25 (A.T.16 is the A.39 Tortoise that we all know and love today)

the A.29 tank "Clan" mentioned earlier is a cruiser tank, not an assault tank
To be fair British tank designations are very hard to make sense of. the A.33 heavy assault tank is very similar in spec to the A.38 Valiant Infantry tank. However this clarification is very helpful.
 

DiePanzerKanone

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A.33 Assault Tank "Commodore"

This is the first time that I've seen the A.33 referred to as the 'Commodore' Do you have a source ?

cheers,
Robin.
It's actually the only name it is called in documentation that have been found so far, Excelsior never has never shown up once apparently. Source is the wonderful article about the A.33 on Tanks Encyclopedia and if you ask anyone who dives in the archives for A.33 stuff they'll tell you (Ed Francis, Slowpoke etc).
 

Iron Felix

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British assault tank projects:
AT 1, 76.2 or 95 mm guns
a39_at1.jpg
AT 2
a39_at2.jpg
AT 3, only machine guns:
a39_at3.jpg
AT 4 and AT 5, machine guns, 4.8" gun (mortar?) and flamethrower:
a39_at4.jpg
a39_at5.jpg
AT 6 and AT 7, 6-pounder gun, 20 mm cannon, and machine guns:
a39_at6.jpg
a39_at7.jpg
AT 8, 6-pdr and 20 mm, MGs:
a39_at8.jpg
AT 9, 6-pdr and 20 mm, MGs:
a39_at9.jpg
 

Iron Felix

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AT 10, 6-pdr and 20 mm, MGs: a39_at10.jpg
AT 13, 17-pdr gun, 20 mm, MGs:
a39_at13.jpg
AT 14, 17-pdr, MGs:
a39_at14.jpg
AT 15, 17-pdr, MGs:
a39_at15.jpg
AT 16 - variant of AT 15 with 37-pdr gun
AT 17 - two flamethrowers
AT 18 - one flamethrower
Evolution from tank, looks like a Churchill/Excelsior/Valiant hybrid, to A39 Tortoise.
 

Grey Havoc

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Because of their intended role in breaching enemy fortified defence lines and other such, the TOG series of tanks were occasionally referred to as Assault Tanks, though they were based around a generally different concept from that described in the opening post.
 
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riggerrob

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Valiant with heavy armour:
View attachment 668435
View attachment 668436
+ bonus. The Russians wanted to install the 85mm S-53 cannon on the Valentine. Why not? Why didn't the British immediately figure out to use the 17-pounder in Valentine and Matilda II? :)
View attachment 668438
Sherman Firefly had an awkward, cramped configuration that required several modifications to the basic 17-pounder gun.
I doubt if a 17-pounder gun could be crammed into a Valentine turret, even the later 3-man turret. Late in the process, some Valentines were built with 75 mm QF guns which shared the same external dimensions and ammo ad the American 75 mm tank gun.
OTOH The Valentine Archer was successful as a 17-pounder, self-propelled anti-tank gun that fought in Italy and Northern Europe (Holland and Northern Germany). The 17-pounder gun was so long that it fired over the engine deck. The crew operated form an open-topped compartment in the front of the hull. Archer could rapidly retreat from an ambush position because the driver was already facing forward.
 

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A39 Tortoise, anyone? More technically a self-propelled gun, but designed for the same requirement that produced the T14 and A33 Excelsior. Weighing in at 80 tons and packing an Ordnance QF 32pdr gun based on the QF 3.7-inch AA gun that (using APDS shot that's not very well documented from what I can find) could credibly take on a Tiger II or even a Jagdtiger. A slightly more practical cousin to the American T28/T95 Superheavy Tank, the war ended before any were delivered, though six were built and tested afterwards. Also featured a rather interesting mini-turret with a pair of Besa machine guns on the top right of the casemate.

Bovington_146_Tortoise_1.jpg post-1_image0-338.jpg
LwLOp5b.png
 

Nik

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Looking at the twin-tracked beasts, I'm reminded of the surviving US behemoth T28 / T95 GMC with its outer tracks in removable sponsons.

Which, IIRC, could be linked side-by-side and towed...
 

0t4n1z3r2020

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I kinda like the design of the US T14 Assault Tank.

Sadly, the Sherman Jumbo is already a working concept despite only an up-armored Sherman.
 

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