United Kingdom (1945)

Cruiser tank – 1 Built

The officially named ‘Tank, Cruiser, A34, Comet I‘, is widely regarded as the finest tank produced in Britain to see combat in the Second World War. Carrying the 77mm HV (High Velocity) main gun in, basically, an improved Cromwell (A24) chassis, the tank combined mobility with firepower.

The design though was not without its flaws. Despite early hopes, it could not mount the formidable 17 pounder gun and the armor was insufficient at the front to protect against the armor piercing (AP) shell fired from the German Panther. This vehicle was considered a significant enough threat that, whilst the next Cruiser tank was being developed, ideas were considered as to improving the Comet, in particular, the armor, to correct this weakness.

Work had begun on the Comet in 1943 but the first deliveries did not start to arrive until the end of 1944. The Department of Tank Design (DTD) was never entirely happy with the compromises made for the design, and the disappointment is reflected in the War Diary of the 29th Armoured Brigade when they received their first batch of the new A34 Comets in February 1945.

“A total of 100 fit Comets had been issued to the Bde [Brigade] by 20 Feb. Everybody was pleased to get the Comet tank, though there were criticisms. Particular disappointment was expressed at the absence of a sloping front glacis plate; however, everyone felt that this tank is a great improvement on the Sherman, and felt honoured that we were the first armoured brigade to be equipped with these new tks [tanks]”.

– 29th Armoured Brigade War diary, February 1945.

It was indeed an improvement for them over the American made M4 Sherman, as the new gun offered the firepower craved to combat German armor, but having gone from a Sherman with the large sloping glacis to the stepped-front design of the Cromwell was seen as a stepback. The armor over the glacis on the Comet was just 32mm thick, albeit steeply angled back leading up to the driver’s plate which was just 76mm thick and vertical.

The reason this driver’s plate was retained was simply that it offered a port for the driver, a mounting for a forward firing hull mounted machine-gun (although the value of such a machine-gun was already in question) and that to change it required a redesign of the hull. Redesigning the hull would have taken time and this vehicle was effectively just a stop-gap awaiting the new Cruiser, the A41 Centurion, so a redesign was out of the question. The question was, therefore, how to improve the armor to provide increased protection against the German 75mm High-Velocity AP round from the Panther tank.

A conference was held on that question and other potential modifications on 3rd February 1945 at the Headquarters of the 29th Armoured Brigade, with a follow-up meeting held at Farnborough just two weeks later on the 17th. The primary complaint was the lack of a glacis, expressed in the report as:

“Some disappointment was expressed that the hull front still had the vertical visor plate and that the sloping glacis plate of the Panther had not yet been adopted. The opinion was expressed that crew would prefer this even if it means that the driver always had to drive through his periscope and hull gun had to be abandoned. It was even suggested that the space set free by abandonment of the hull gunner should be used for the stowage of additional 77mm ammunition”

The Department of Tank Design, however, did not seem swayed by the demand for a sloping front glacis. The design of the German Panther tank had significantly affected the thoughts of men who had faced them in combat but not yet those at the DTD. Perhaps unwilling to abandon the hull machine-gun, they suggested instead a compromise of adding an additional 1″ (25.4mm) of armor plate to the 3″ (76.2mm) vertical visor plate, bringing it up to 4″ (101.6mm) across that part. The DTD were clearly unhappy with even this compromise though as they demanded further trials to see what difference this additional weight might make on the vehicle.



A24 Cromwell tank front armor. 64mm vertical plate over 25mm sloped glacis.



A34 Comet hull with new 25mm thick sloped glacis.

A34 Gets its Glacis

Adding just another inch of armor to the three the Comet had would leave it with four inches of armor on its vertical plate, which would still not provide the protection from the German gun. The following solution was simpler – do what the soldiers wanted. Remove the hull machine-gun and accept a restricted driver’s view for additional protection. The other advantages of this being the removal of the hull gunner and additional space for ammunition in the front left of the hull. The turret still retained its machinegun, so the loss of the one in the hull was of no significance compared with being able to carry a dozen or more shells for the primary armament and increased armor. The question had therefore become what thickness of a plate was needed.



A34 Comet with 25mm thick plate fastened by bolts to the front of the hull of an existing Comet. The turret is turned backward to avoid damage. Photo: PM Knight

The plan was to use a single 25mm thick plate made from I.T. 80 armor steel (the same as the tank hull’s primary armor) angled at 49 degrees from the horizontal over the front of the Comet from the nose to above the visor. The plate was fixed by means of three steel brackets welded to the old glacis to which the new glacis plate was fastened with 3 rows of 6 bolts each.



The A34* (Star) Comet. Note the added plate at the front of the tank. Illustrated by Alexe Pavel, based on an illustration by David Bocquelet.

Testing

For the purposes of the test, rather than remove the BESA machine-gun mount and plate, it was added over it, as would have to be done if the modification was adopted; the mount was simply left in situ. The test Comet was shot at using the German 7.5 cm KwK 42 L/70 gun as mounted in a captured Panther tank brought to Shoeburyness Ranges. The round fired was the Panzergranate 39/42 Armour Piercing Capped Ballistic Capped (APCBC) shell at 2578 fps (785.8 m/s). The results were perhaps predictably poor, this 25mm plate effectively made no difference. The shell pierced both it and the original visor behind it completely. A second shell penetrated both the new glacis plate and the original glacis plate behind it completely as well.

A 25mm plate angled at 70 degrees should have provided an equivalent of an additional 38mm of armor on the visor plate and an additional 13mm on the glacis and a 45mm thick (32mm + 13mm) glacis should not have been penetrated by the shell traveling below 2700 fps (823 m/s), yet both areas had been penetrated by a shell some 122 fps (37.2 m/s) slower.

The target was then moved 30 degrees to the side to test for oblique impacts. Two shots were fired at the upper part of the new glacis with the original visor behind. The first shot only penetrated the outer plate and did not penetrate the original visor, but a second shot penetrated both layers of armor even at this angle. Two more firings were carried out at the lower section of the new glacis and the results were not good. A firing limit of 2600 fps (792 m/s) equivalent to 1000 yards was established for this area of armor. The improvement of the new glacis was marginal. Head-on against this shell the plate made no difference at all and was completely penetrated at test ranges. When the vehicle was angled 30 degrees to the line of fire from the enemy vehicle this new armor added just 130 fps (40 m/s) equivalent to a range of 200 yards (183 m) to the protection of the vehicle compared to the original armor scheme

In summary, the firing trials determined that:

“Against normal attack from 7.5cm A.P.C.B.C, the additional protection plate is inferior to plates of equivalent thickness in contact with the visor and glacis, but against 30 degree attacks the protected offered to the visor is slightly higher than that given by an equivalent increase in thickness”

The protection plan was simply not as effective as it was thought it would be. The sloping glacis should either have been thicker and uniform comprising the entirety full frontal armor, or the equivalent armor 25mm simply added to a 76mm visor and 32mm glacis by welding it on as applique and retaining the stepped shape. Other than at very oblique angles this would be superior to this unusual spaced-armor glacis arrangement. It would also retain the bow machine-gun and the driver’s port.

Head On

30-Degree Oblique Impact

End

The tests were a failure. The German gun was too powerful even for this temporary fix of a temporary tank. The thinking had been good, but there was to be no substitute for a properly angled plate of the correct thickness in the first instance. For that, the British would have to wait for their A.41 afterall. A tank which became a legend in its own right, albeit, one too late to ever fight the Panther itself.



The solution to the sloping front problem. The Mk.1 Centurion also featured the more powerful 17 pounder gun.

Despite the visor being substantially thicker than the glacis, the tests had shown the vulnerability of the visor plate as it was penetrated by enemy fire from that shell even out to 2650 yards (2423 m). The whole of the frontal hull armor could still be penetrated even when angled at 30 degrees, but with the glacis plate the visor and glacis were only penetrate-able at 1000 yards (914 m) instead. For the Department of Tank Design, the problems with losing a hull machine-gun and obstructing the driver’s view just outweighed any merit. The increased protection demanded could be simply provided by welding on 25mm of applique to the front anyway. The age of the stepped front tank was over.

It was felt by the Army that certain tactical roles, presumably the same sort which required the use of the 95mm howitzer like the C.S. (Close Support) role, would benefit enormously from this increased level of protection but the DTD were not to be swayed. The testing had not shown the benefits to outweigh the drawbacks and the project was nixxed and forgotten about. The A41 provided a single glacis thicker and stronger than this attempt and Comets were replaced in service as Centurion were delivered.

Note

Although the article refers to this vehicle as ‘A34*’ there is no information available as to what any official name for this vehicle would have been had she entered service although an asterix is a common British addition to a name to denote a technical modification.

Specifications Dimensions

L x W x H 6.55 m x 3.04 m x 2.67 m

(21ft 6in x 10ft 1in x 8ft 6in) Total weight, battle ready 33.53 tonnes (32.7 long tons) Crew 5 (commander, driver, gunner, loader/radio op, hull machine gunner) Propulsion Rolls Royce Meteor Mk.III V12 Petrol/gasoline engine, 600 hp (447 kW) Suspension Christie system Top speed 32 mph (51 km/h) Range (road) 155 miles (250 km) Armament 77 mm (3.03 in) High Velocity gun, 61 rounds

2x 7.92 mm (0.31 in) BESA machine guns, 5,175 rounds Armor From 32 to 102 mm (1.26-4.02 in) + 25mm (0.9 in) glacis plate Total production 1,186

Links & Resources

A.34 Comet – A Technical History, PM Knight

29th Armoured Brigade War diary

Report from a meeting at the Headquarters of the 29th Armoured Brigade, 17th February 1945