Comet tank development

[Petrus]

1.

In the "British Cruiser Tank A34 Comet" (Armor Photogallery No. 20) book its authors Dick Taylor and Chris Hughes make two interesting remarks on how the Comet tank would have looked like:

When the Comet was designed the intention was to make it as similar in construction to the in-service Cromwell as possible, to avoid disruption when switching production to the new type. Because of this, the opportunity was missed to give the Comet a sloped glacis plate in the style of the Panther or T-34, which would have increased its frontal armor protection. It would also have allowed the fifth crew member (the co-driver/bow machine gunner) to be removed and thus created much more space for main armament ammunition to be stowed.

Because of the direct link between the Cromwell and the new tank, and the need to be able to implement A34 production without discrupting existing manufacturing, a sloped glacis plate was not adopted, although this came in for later critisism. Many RAC soldiers and officers wanted a sloped glacis for increased protection, as well as the elimination of the co-driver and his BESA to allow more main armament ammunition to be carried.

Do you have any idea if any sketches (drawings) of such a variant of the Comet actually exist? Perhaps you have heard of this variation of the project and have further info. If so please let us know.

2. Another question.

In lists of British tank designs of WW2 you may find A44 project. Usually it's being described as "Projected Comet with 17pdr and larger turret ring" or "Project for "Comet" with larger turret ring to take 17pdr gun. Cancelled". One website states that its turret ring was to have a diameter of 57.2in (fifty seven point two inches), which seems rather unlikely as the Comet's turret ring was 64in (sixty four inches) so "larger turret ring" should have had more than this, don't you think?

Unfortunately I could not find any further information on A44 project. How about you? I would be grateful for any information, including pictures of course.

Thank you in advance for your help.

Best regards,
Piotr

 

[Rickshaw]

I doubt a larger turret ring was absolutly necessary. However, a larger turret may have been, considering the difference in length between a 17 pdr and a 77mm round.

 

[Petrus]

I am afraid that making the turret ring wider was essential so as a bigger gun can be mounted in the turret.

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)

The 17pdr used 76.2 x 583 cartridges while the 77mm gun, which armed the Comet - 76.2 x 420 (I haven't info on the cartridges' overall length), the former's breech must have been proportionally longer as well as its recoil distance bigger, so the 17pdr required more space within the tank's turret.

Best regards,
Piotr

EDIT:
* The Sherman, naturally, was a British tank in the sense it was being used by the British army.

 

[JohnR]

If Challengers turret diameter was 70", an inch wider that the Sherman, then why was it necessary to have the large and cumbersome turret?

 

[Petrus]

If I am not mistaken the Challenger was armed with 17pdr Mark II gun while the Sherman had a specially modified version, according to some sources designated as Mark IV, that could be squeezed into its turret.

This is what Wikipedia says on the issue:

It was W.G.K. Kilbourn, at the time working for the Department of Tank Design, who would transform the prototype into the tank that would serve the British forces from D-day onwards. The first thing Kilbourn had to fix was the lack of a workable recoil system for the 17 pounder. The 17 pounder would travel 40 inches back as it absorbed the recoil of the blast. This was too long for the Sherman turret. Kilbourn solved this problem by redesigning the recoil system completely rather than modifying it. The recoil cylinders were shortened to allow the turret to take the gun and its recoil, and the new cylinders were placed on both sides of the gun to take advantage of the width of the Sherman's turret rather than be hindered by its height. The gun itself was also rotated 90 degrees to allow for left handed loading.

The next problem encountered by Kilbourn was that the gun cradle, the metal block the gun sits on, had to be shortened to allow the gun to fit into the Firefly, and thus the gun itself was not very stable. Kilbourn had a new barrel designed for the 17 pounder that was wider at the base, which helped solve the stability problem. A new mantlet was designed to house the new gun and accept the modified cradle. Thus, while the 17 pounder for the Firefly was a modified variant, it would have to be factory built specifically for it.

As I understand it the Challenger's turret was still too narrow, so it must have been quite high to accomodate all the 17-pdr's mechanism (esp. recoil brakes).

Piotr

 

[JohnR]

Slightly off topic, but what was the turret ring diameter of the Centurion?

 

[Petrus]

The Centurion's turret ring was 74in (1880mm) wide. I am sure it regards the early marks, but the later, if I'm not mistaken, retained this without change.

Piotr

 

[merlin]

Going back to the first post - if a 'sloped' front had been adopted, there is a danger because of the difference to the Cromwell, it may delay production - so that like the Centurion it is too late to see service!

 

[kaiserbill]

Some further info at the potential of modifying the Comet glacis I stumbled upon.

http://www.tanks-encyclopedia.com/coldwar-uk-comet-cruiser-tank-a34-star/

 

[Foo Fighter]

Hmmm, talk about prejudice, did you read the post by the moderator' talking about sloped armour and less space? I have to say that is an "Ahhh bless" moment.