Tank, Cruiser Mk.VIII 'Challenger'
UK (1943) - Tank Hunter - 200 built
The British stopgap tank killer
Stuck between the Cromwell and the Comet, this 1942 program, headed by Roy Robotham, was meant to carry the long 17-pdr gun. On paper, this was quite a formidable anti-tank gun, but incompatible with the turrets of the Crusader and Cromwell series. It was realized that the new tanks (Comet and later Centurion) would need at least two more years of development, so an interim solution was chosen with the modification of a Cromwell tailored to carry a larger turret ring for the 17-pdr.
This resulted into the A30 design, basically a stretched-out Cromwell with an extra pair of roadwheels and many other modifications, including the removal of the bow machine gun to free space for the bigger rounds. The new turret was taller and, due to the strain added, compromise led to it having thinner armor than actually found on the Cromwell.
A30 official presentation
After production started in February 1943, with 200 Challengers built by Birmingham Railway Carriage and Wagon Company, the General Staff declined any further order and canceled the project in November of that year. The few Challengers built acted as tank hunters until the end of the war. They arived in operations in August 1944 in Normandy, then northern France and the Low Countries. Many served with the 1st Czechoslovak Armoured Brigade and 22 were found in service in the Czechoslovak army until 1951 when provisions of Soviet-built tanks made it obsolete.
Development of the Challenger
The man behind the whole concept was W. A. Robotham. A Rolls-Royce executive in the car division he was responsible for the powerplant that produced two legendary mechanics, the Rolls-Royce Merlin and the Meteor. The first was used on two war-winning allied fighters, the Spitfire and the Mustang, the other on fast British tanks such as the Cromwell. Powerful and reliable engine, it gave the Cromwell an advantage over the Sherman and was arguably the best British tank until the arrival of the Comet at the end. It also gave Robotham a promotion as Ministry of Supply in the tank board. He can push on for whatever type of tank he wanted.
After the North African Campaign in early 1943, the General Staff drafted the specification A29, asking for the development of a 45 ton, 17 pounder armed cruiser tank. That was the next logical step, expected to carry the famous 17-pdr. At the ame time the campaign of Tunisia was drawing to an end, it was generally accepted that the 6-pdr QF was longer up to the task against the latest German hardware, and a provisional mount for the brand new Royal Ordnance gun, called "Pheasant". The barrel was simply mounted into the existing 25-pounder gun-howitzers carriage.
The first 100 saw action in February 1943 and proved their immense superiority over previous guns. But the baptism of fire really came out during the Italian campaign. Wherever it was available, the 17-pdr (76.2 mm) was found able to penetrate frontally any German tank, more than 100 and up to 275 mm depending on the ammunitions, to ranges up to 3000 m. This was the piece needed in future battle tanks as soon as possible.
The 17 Pdr was so promising it was pressed into a variety of platforms that were in many cases buuilt around it, the time for designers to create a more manageable recoil and breechblock to fit inside a turret. Meanwhile, the 17-Pdr found its way into the Valentine/Archer tank hunter (fixed), of which 600+ were delivered until the end of the war, and conversions of existing tanks such as the famous Sherman Firefly (more than 2,000), 17pdr SP Achilles based on the M10 GMC, or experiments such as the Black Prince (A43), TOG-2 and Australian Cruiser tank Mk IV (which was the first to test it).
The next cruiser type (VIII) was therefore to carry it as well. However the 45 tons weight was considered too heavy and unmanageable for a medium, and specifications were revised down to 35 tons. The new project was named A30. To gain time in 1942, the Birmingham Railway Carriage and Wagon Company, in charge already of the future Comwell, was contacted to deliver a prototype using existing resources, notably reusing as much Cromwell components as possible. The first step of the company was to elongate the Cromwell chassis, integrating an extra axle. Meanwhile, design and construction of the turret and gun mounting was given to Stothert & Pitt.
The latter were renown dock cranes manufacturer and already well experienced in casting, welding and heavy metal structures, but never went into tank production. They will have their hands also on the Avenger, an attempt to devise a lighter, lower turret, and the TOG-2 turret. However the program advanced slowly. Meawnhile it was expected the Cromwell could be upgraded to the 17-pdr.
However by May 1943, all attempts to cram the new gun into the existing turret failed. With the gun reported to a possible successor in line to the Crowell, the A30 project received traction again and the team was pressed on to complete a prototype. Despite the best efforts, the Vickers 75 mm L/50 already never fit into the turret, as its ring was too small, but the turret ring on the new A30 chassis was larger and it became a stopgap project waiting for the next A34. However at this point British resources were quite limited.
Criticisms about the turret went on unabashed in reports during tests of the three prototypes delivered in May 1942: The first was inspected by the Tank Board (Farnborough, 13 August), the second much later at Lulworth (21 January 1943). The turret was shown difficult to traverse when the hull was tilted across a slope. Chief Inspector at Lulworth considered the entire project "a pointless waste of effort". That view was shared by many officers which were concerned about the weakly protected turret, tall sihouette and large dimensions. But also because the future course of German tank design was unknown at that time. Conclusions were ignored as it was too late already to redesign the turret and in February 1943, 200 were ordered.
At the time of D-Day, this batch was ready since a whilen training whenever possible in the British countryside. It was already found the conversion of existing Shermans save a lot of time and resources and decided to terminate the A30 program. This way, both companies could concentrate on improving the Crowmell instead.
Development of the Challenger
The major design headache of the project headed by Robotham was the lenght of the new 17-pdr rounds, almost twice as heavy than 6-Pdr QF rounds, or even longer than regular 75 mm Sherman ammunition. Space had to be found inside the turret, and for this the Tank Board agreed to sacrifice the coaxial machine-gun. The Tank would defend itself with its ball-mounted hull machine-gun. Another problem soon emerged, the rounds were two-pieces, with a separate propellant charge. So it required two loaders instead of one, that had to be inside the same turret. It could no longer be a three-man model. Thefeore the turret design became bloated, with nothing in common with the Centaur/Cavalier/Cowmell standard model.
The turret not only had a larger turret ring, but it was shaped in a lozenge, with a vertical opening for the gun mantlet, which was internal. The turret sides were entirely cast, with a flat roof welded on top. The opening allowed an elevation which was quickly reached when the Breech block reached the latest security distance deep inside the turret basket. The base of the turret was unprotected, and it was expected to clear jams with a semi-automated system. Protection of the turret was minimal as the weight was controlled. Walls therefore were vertical, but the front section was reduced and rounded. The sides were flat, and to keep the weight down the rear section was cut into a narrow end. The back wall was opened in the middle for a gun ejector hatch, to evacuate spent casings and reload supply.
On the turret roof there were three periscopes, a commander cirtcular two-piece hatch on the right and gunner's rectangular two-piece hatch right. There also behind both hatched two episcopes and two "mushrooms" gas extractors. The antenna was welded on the rear-left corner plate. The hatches were about the same, as much as the rest of the equipment, as on the Cromwell turret to simplify production. But the turret height was about 40% higher compared the latter.
It offered a conspicuous target to the enemy, placing it on par with the Sherman. But the prize was an Ordnance QF 17 pounder (76 mm) supplied with 42 rounds of various types. In 1944, the APDS was by far the faster and longer range. It was an early "arrow" design with discarded sabot, able to pierce through 120 mm of hardened steel at 3000 m. This placed it on equal foot to the Panther and Tiger.
Hull and Mobility
The hull was quite similar to the Cromwell, except for an extra wheel station and Christie suspension arm in the section under the turret ring. Another difference was some space was gained in front of the ring, allowing to use larger hatches compared to the Cromwell, and better clearing space for the driver and co-driver, giving them surviving chances. The problem with lenghtening the hull with the same engine was not much a loss in performances, as the chassis was as fast as on the Cromwell (with the same engine) at 25 mph. But rather an agility problem.
The tank was turning on a greater distance and more slowly. The engine compartment housed the same standard Rolls-Royce Meteor V-12 petrol engine, rated for 600 hp (450 kW), 18.8 hp (14 kW)/tonne ratio, a top speed of 32 mph (51 km/h) and a range of 105 mi (169 km).
Measures were taken to keep some mobility: The weight of the turret was such that heavy strain was put on the engine, and accelerations and torque were comparatively lower. It was decided that the additional weight in the turret could not be lifted of the hull because of strength concerns, and there was only one way: Decreasing protection of the turret. This was done by having thinner walls, 63 mm (2.5 in) on the front (75 mm (3.0 in) on Cromwell), and 40 mm (1.6 in) on the sides (60 mm on the Cromwell).
The Challenger in action
The first concern about the arrival of the much-needed 17-pdr carrying tank was the"floating" in communication within Robotham's offices as well as between him and the hierarchy. Much of it was due to the prolongated development of the A29, and its lack of progress eventually spurred the development of the A30 which was rushed to production. To the confession of Robotham hismelf he was unaware or unsure what priority was given to the project, since discussions were still going on with the Americans, now supplying in large quantities the Sherman, an artillery tank capable of anti-tank duties rather than the contrary.
British tanks were often given that anti-tank role. Another difficulty was that the Challenger was produced at the same time and place as the Cromwell, and it was envisioned that the latter would adopt the same American versatile 75 mm. Eventually the development of the Firefly cared for this much needed task and the Challenger was caught in between and when news of deployments of the converted Sherman reached the general staff, the Ghallenger wwas terminated: The Firefly was a much better suited platform as a stopgap tank killer, waiting for the Comet to arrive. But this gap was resented by British crews which felt they were sacrificed with woefully inadequate tanks, with the exception of the Churchill and Matilda, which could survive many hits. In this area, the Firefly fared no better than regular Shermans, and this was the policy of "see first, hit first".
Entry into service
Production records showed the vehicles were delivered late 1943 (and the information came in November that no more would be ordered), time for tooling up after the initial order, entering service in early 1944, disturbed by the production rythm of the Crowmwell, both model sharing many components. When delivered, they joined training units in Uk, preparing already for D-Day. However in May already, it was known they lacked deep wading equipments and there was no time left for their modification. In June, they stayed home, waiting for the Mulberries to be built. Meanwhile, the Firefly was already rampaging the bocage. Organically, they were distributed among Cromwell tanks units, to ease maintenance and supply, and comparatively the same numbers of Firefly tank hunters went with the more numerous Sherman-equipped units, for the same reasons.
A contest of tank hunters
When the Challengers arrived on the front at last, two years had passed since the idea of a 17-pdr tank was first drafted. Despite its obvious shortcomings, the Challenger was more appreciated overtime by the crews, which had at least a fighting chance. The Challengers's performances were about the same as the Firefly; They could engage victoriously head one Tiger I and Panther tanks, and were pressed to do so whenever these particular tanks were spotted. On the other hand, they were faster than the Panzer-IV, and STUGs, not mentioning the lumbering Tiger, faster even than the Firefly, the gun had twice its depression, and a lower hull, less easy to pickup. However what the crew did not liked, outside the light and tall turret, was the propension of the tank to throw its tracks when turning at high speed.
However, suspensions were more modern, and the Rolls-Royce Meteor engine generally more reliable than the venerable Continental of the Sherman-based Firefly. All in all it seems the crew preferred it over the Firefly. But despite of this, we have little records of action, and number of kills. The tanks were constantly at work with Cromwells whenever they were deployed, such as the Falaise pocket, and later the Rhine, the Belgian coast and Holland.
Nevertheless, in upper circles, the Challenger was considered almost as a bit of embarassment, and after the crossing of the Rhine and a first batch was sent to the 1st Czechoslovak Armoured Brigade, which used it during the siege of Dunkirk (late 1944) and about April-May 1945, others went to the Polish 1st Armoured Division. By that time the Comet had replaced both the Cromwell and Challenger, and there was no use for it. Eventually the A30 became war surplus and was stockpiled after the war, waiting for disposal and long term scrapping. However, 22 Challengers were purchased from the brigade inventory, by the new Czechoslovak army: They equipped the 11th tank brigade, and later the 23rd Tank Brigade, to end with the 13th Independent Tank Battalion, discarded in 1951. They only left the reserve to be scrapped in 1959. As a stopgap model, there was no use for them in the cold war...
The Avenger (1945)
The main criticism about the A30, the turret, did not fell into deaf ears. It was soon thought that it could be lowered in some way, and made it better protected. This was to give a modified variant called the SP 17pdr, A30 (Avenger). Officially it was a self-propelled gun, belonging to the same category as the Archer. This meant that the engineers only solution was to provide a new simplified turret, driven by the main engine, solving much technical issues.
The second loader's position was eliminated, an additional stowage bin fitted on the glacis plate with a camo net for ambushes, and additional return rollers were fitted. The turret was basically the same, but halved, leaving an open top, which provided, just lke the American tanks hunters such as the M10 and British Achilles, an excellent 360° vision. To protect them and the compartment from the elements, a hard metallic canopy incorporating hatches was welded above the opening. Also the weight spared could be redistributed in protection, making the turret front and sides much tougher.
The new tank hunter was hastily completed, the first pilot ready in late 1944 and 500 ordered, which apparently went down to 230 to BRC&W, and in mid-1945 it was reduced to 80 eventually. Production figures are difficult to establish as official records placed its numbers delivered mixed with Archers and Alecto self-propelled guns, noted as SP2. Perhaps two dozens were manufactured, or less, according to the rare photos found.
According to Mitch Williamson, the order of 230 vehicles was fulfilled in 1946 and they equipped two Self-Propelled artillery battalions after the war. Trials went up to 1950. Winter trials in particular, showed that moving the turret by using the engine took a toll on the later but was overall noisy, contradicting any attempt of concealment. In the end trials were not succesful and the model was never pressed into service. They were all scrapped, as none survived.
This is not the case for the Challenger, with two preserved, restored, one in Holland, at Overloon museum, and the other in the Isle of Wight Military Museum, prending restoration before joining the Bovington collection.
First British operational unit training in UK, may 1944
1st Armoured Division, 10th Mounted Rifle Regiment Strzelcow Konnych, Feb-March 1945.
Czechoslovak Independent Armored Brigade (CIAB), 1st Armoured Batallion, Prague, May 1945.
CIAB 1st armoured batallion Prague May, 30, 1945
A30 'Avenger', December 1944.