Cromwell tank

Tank, Cruiser, Mk VIII, Cromwell (A27M)

Cromwell Mk IVd in the Kubinka Tank Museum
Type Cruiser tank
Place of origin United Kingdom
Service history
In service 1944–1955
Used by British Army, Israeli Army, Greek Army, Portuguese Army
Wars World War II, 1948 Arab–Israeli War, Korean War
Production history
Designer Leyland, then Birmingham Railway Carriage and Wagon Company from 1942[1]
Manufacturer Nuffield Mechanisation and Aero
Number built 4,016
Specifications
Weight 27.6 long tons (28.0 t)
Length 20 ft 10 in (6.35 m)
Width 9 ft 6 1⁄2 in (2.908 m)
Height 8 ft 2 in (2.49 m)
Crew 5 (Commander, gunner, loader/radio operator, driver, front gunner)
Armour 3 inches (76 mm) on Mk.IV, 4 inches (100 mm) on Mk.V
Main
armament
 Ordnance QF 75 mm
with 64 rounds
Secondary
armament
 2 x 7.92 mm Besa machine gun
with 4,950 rounds
Engine Rolls-Royce Meteor V12 petrol
600 hp (450 kW)
Power/weight 21.4 hp/tonne
Transmission Merritt-Brown Z.5 gearbox (five forward and one reverse gear) driving rear sprockets
Suspension Improved Christie
Ground clearance 16 inches (410 mm)
Fuel capacity 110 imp gal (500 l) + optional 30 imp gal (140 l) auxiliary
Operational
range
 170 miles (270 km) on roads, 80 mi (130 km) cross country[2]
Speed 40 mph (64 km/h) with 3.7:1 final reduction drive

The Cromwell tank was one of the most successful of the series of cruiser tanks fielded by Britain in the Second World War. Named after the English Civil War leader Oliver Cromwell, the Cromwell was the first tank put into service by the British to combine a dual-purpose gun, high speed from the powerful and reliable Meteor engine, and reasonable armour, in a balanced package. Its design formed the basis of the Comet tank. The Centaur tank was a vehicle closely related to the Cromwell, both vehicles being externally of very similar appearance.

Officially known as the Tank, Cruiser, Mk VIII, Cromwell (A27M),[lower-alpha 1] and Tank, Cruiser, Mk VIII, Centaur (A27L) the Cromwell and Centaur differed in the engine used. While the Centaur had the 340 hp Liberty engine of the preceding cruiser tank, the Crusader (and the interim A24 Cavalier), the Cromwell had the significantly more powerful 600 hp Meteor. Apart from the engine and associated transmission differences, the two tanks were the same and many Centaurs were later fitted with the Meteor to make them Cromwells.

The Cromwell first saw action in the Battle of Normandy in June 1944. The tank equipped the armoured reconnaissance regiments of the Royal Armoured Corps, in the 7th Armoured Division, 11th Armoured Division and the Guards Armoured Division. While the armoured regiments of the latter two divisions were equipped with M4 Shermans, the armoured regiments of the 7th Armoured Division were equipped with Cromwell tanks. The Centaurs were not used in combat except for those fitted with a 95mm howitzer, which were used in support of the Royal Marines during the invasion of Normandy.

Development

Initial designs

Development of the Cromwell and Centaur dates to 1940, as the Crusader tank was being readied for service. The General Staff was aware that the Crusader would become obsolete, and in late 1940 they set out the specifications for the new tank to replace it. The tank was to be fitted with the QF 6 pounder gun and was expected to enter service in 1942.

Vauxhall responded with the A23, a scaled down version of their A22 Churchill infantry tank. This would have had 75 mm of frontal armour, used a 12-cylinder Bedford engine, carried a crew of five and would have the same suspension as the A22.

Nuffield submitted the A24, heavily based on its Crusader design and powered by its version of the Liberty engine, a V-12 design dating the late days of World War I and now thoroughly outdated. Nevertheless, as the design was based on the Crusader, it was expected it could be put into production rapidly.

The final entry was from Leyland and Birmingham Railway Carriage & Wagon (BRC&W). Their design[lower-alpha 2] was similar to the Nuffield, but with different suspension and tracks.[3]

The designs were received and examined in January 1941, with Nuffield's A24 being declared the winner on 17 January. Six prototypes of the Cromwell I were ordered for the spring of 1942. These arrived four months late and by this time the design was already outdated. It was put into production anyway, but in service it proved entirely underpowered and only a small number were built.

Delays in the A24 program led to demands to get the QF 6 pounder into service earlier. This led to a series of up-gunned Crusaders mounting the 6-pounder.[4]

A27

With the start of the war, Rolls-Royce ended car production and set up a design team looking for other ways to use their production capacity. The team formed under the direction of Roy Robotham at Clan Foundry near Belper, north of Derby. In October 1940 Robotham met with Henry Spurrier of Leyland Motors to discuss British tank design. They decided to attempt to fit a Rolls-Royce Merlin engine to a Leyland tank for testing. They removed the supercharger from a Merlin Mk. III and fitted it to a Leyland-built Crusader. Delivered to Aldershot on 6 April 1941, the test team had trouble timing its runs because it was so fast, estimating it reached 50 miles per hour (80 km/h).

Everyone was so impressed by this display that Leyland arranged to start production of 1,000 examples of the engine as the Meteor. They planned to fit this to BRC&W-built versions of their original A24 submission. However, in mid-1941, Leyland changed its mind, concerned about cooling problems. They instead suggested using a diesel engine of their own design, although this would produce only 350 horsepower (260 kW) compared to over 500 from the Rolls design. The Tank Board then placed an order directly with Rolls for the Meteor. The resulting design was ordered as the A27. When Leyland suggested that the tank be designed to fit either the Meteor or the Liberty, the two versions were given the General staff numbers A27M and A27L, respectively, and the names Cromwell III and Cromwell II. The diesel concept was abandoned.

The first prototype of a Meteor-powered Cromwell III was delivered in January 1942, several months before the A24 that was supposed to precede it. With nearly 600 hp (450 kW) it proved to be exceptionally mobile when tested. Orders were placed for both versions, as there were concerns about the production rate of the Meteor. Even when assigned reduced production quotas, BRC&W proved unable to meet demand, and Leyland eventually took over production of both versions.

Rover enters

Rolls was at this time having trouble meeting demand for the Merlin, let alone the Meteor. Meanwhile, Rover was having troubles developing Frank Whittle's Power Jets W.2 jet engine design due to increasing animosity between the engineers at Power Jets and Rover. Things became particularly heated when Whittle learned that Rover had set up a secret lab to develop their own versions of the design. Whittle had, during the same period, contacted Rolls for help delivering some of the required parts that Rover proved unable to produce.

A solution to both their problems was offered by Ernest Hives, a Rolls board member, who had met Whittle and was fascinated by the jet engine. Hives called a meeting with his counterpart at Rover, Spencer Wilks, and the two met late in 1942 at the Swan and Royal pub in Clitheroe. Hives offered to trade the Meteor for the W.2, an offer Wilks jumped at. The official handover took place on 1 January 1943. Rover set up production at their Tyseley factory, and an additional line was set up by Morris Motors in Coventry.

Production began in November 1942. That month, new names were given to all three designs; the original A24 Cromwell I became the Cavalier, the Liberty powered A27L Cromwell II became Centaur, and the Meteor powered A27M kept the name Cromwell. It would take considerable time for Rover to make ready production lines for the Meteor, and it was not until a few months later, in January 1943, that sufficient Meteor engines were available and the A27M Cromwell began production. The Centaur production design allowed for the later conversion to the Meteor engine and many Centaurs were converted to Cromwells before use.

Final changes

The first real field test of the design was carried out in August–September 1943, when examples of the Centaur, Cromwell, Sherman M4A2 (diesel engine) and Sherman M4A4 (multi-bank petrol engine) were all tested in Exercise Dracula, a 2,000 mile long trip around Britain. The Shermans proved to be the most reliable, by far, requiring 420 hours of specialist fitter attention over a total distance travelled of 13,986 miles (22,508 km). This corresponds to 0.03 hours per mile. In comparison, the Cromwells drove 11,582 miles (18,639 km) and required 814 hours, or 0.07 hours per mile. The Centaur managed only 8,492 miles (13,667 km) due to constant breakdown, and required 742 hours, or 0.087 hours per mile.[5]

The Cromwell and Centaur were given additional time to work out these problems. The Cromwell's problems were mostly related to oil leaks and brake and clutch failures, an observer noting that these were well-known and should already have been corrected. The crews, however, expressed their love for the design, and especially its speed and handling. The Centaur was largely dismissed, with one observer expressing his hope that units were being equipped with it only for training purposes. The same reviewers unanimously supported the Sherman.[5] A similar test in November demonstrated the Cromwell was improving, while the underpowered Centaur fared no better than the first test.

The production model design was finalised on 2 February 1944 when Leyland released specifications for what they called the "Battle Cromwell". This included a number of minor changes to the basic design, including 6 millimetres (0.24 in) of extra armour below the crew compartment, seam welding all joints to waterproof and strengthen the tank, and standardizing on the Meteor engine and Merritt Brown transmission.

Production

Total A27 production consisted of 4,016 tanks, 950 of which were Centaurs and 3,066 Cromwells. In addition, 375 Centaur hulls were built to be fitted with an anti-aircraft gun turret; only 95 of these were completed. Several British firms besides Leyland contributed to production of the Cromwell and Centaur, including LMS Railway, Morris Motors, Metro-Cammell, Birmingham Railway Carriage and Wagon Company and English Electric.[2]

Design

Silhouettes of M4 Sherman (top) and Cromwell (bottom) together

The frame was of riveted construction, though welding was used later. The armour plate was then bolted to the frame; large bosses on the outside of the plate were used on the turret.

The suspension was of the Christie type, with long helical springs (in tension) angled back to keep the hull sides low. Of the five road wheels each side, four had shock absorbers. The tracks were driven by sprocketed wheels at the rear and tension adjusted at the front idler, this being standard British practice. Some variants were produced with 14-inch-wide (360 mm) tracks; later, 15.5-inch tracks were used. As with previous Christie-suspension cruiser tanks, there were no track return rollers, the track being supported instead on the tops of the road wheels, known as the "slack-track" design. The side of the hull was made up of two spaced plates, the suspension units between them, and the outer plate having cutouts for the movement of the road-wheel axles.

The gearbox had five forward and one reverse gears. The first gear was for "confined spaces, on steep inclines or...sharp turns". The transmission was the new Merrit-Brown Z.5, which offered differential steering without clutching or breaking, a major advance on previous designs. It gave the Cromwell superb maneuverability, with only the German Tiger I, using a similar design, able to match it. The Meteor engine delivered 540 hp at 2,250 rpm. This was the maximum rpm, which was limited by governors built into the magnetos. Fuel consumption on "pool" petrol (67 octane) was between 0.5 and 1.5 miles per gallon depending on terrain.

The driver sat on the right in the front of the hull, with the hull gunner on the left, separated by a bulkhead. The driver had two periscopes and a visor in the hull front. The visor could be opened fully or a small "gate" in it opened; in the latter case a thick glass block protected the driver. A bulkhead with access holes separated the driver and hull gunner from the fighting compartment. A further bulkhead separated the fighting compartment from the engine and transmission bay. The engine compartment drew cooling air in through the top of each side and the roof and exhausted it to the rear. To allow fording through up to 4 ft (1.2 m) deep water, a flap could be moved to cover the lowermost air outlet.[6] Air for the engine could be drawn from the fighting compartment or the exterior; it was then passed through oil bath cleaners. It was modified so that the exhaust fumes were redirected so that they were not drawn into the fighting compartment, a problem found when tanks were drawn up together, preparing to advance.[7]

The Cromwell had revisions to make before service, changing from the QF 6-pounder (57 mm) to the ROQF 75 mm gun, which was an adaptation of the 6-pounder design to fire the ammunition of the US M3 75 mm gun, which gave it a better HE round to use in infantry support. This meant that the 75 mm used the same mounting as the 6 pounder. In June 1944, the Cromwell saw action during Operation Overlord, the Allied invasion of Normandy. It had a mixed reception by crews, being faster, with a lower profile than the Sherman tank and thicker frontal armour plate 3 in (76 mm) as against the 2 in (51 mm) on the glacis of the early Shermans, though it was unsloped and hence less effective.[8] On later Cromwells this was increased, first to 3 1⁄4 in (83 mm), then to 4 in (100 mm). The 75 mm gun, though able to fire a useful HE shell, was not as effective against armour as the 6-pounder or the Ordnance QF 17 pounder gun. A derivative of the Cromwell, the Cruiser Mk VIII Challenger, was built to take the 17-pounder; but only a small number were built. Most 17-pounder armed tanks to see service in the war were the Sherman Firefly variant of the Sherman.

There was a 7.92 mm Besa machine gun mounted co-axially to the main armament, operated by the gunner. A second was "gimbal" mounted in the front of the hull, with 45 degrees horizontal and 25 degrees vertical movement. Sighting was by a No. 35 telescope, which was connected through a linkage to the mounting. In the top of the turret was a 2 inch "bombthrower" angled to fire forward and thirty smoke grenades were carried for it.

Performance

A King's Royal Hussars Cromwell of the 11th armoured division advances through Uedem, Germany, 28 February 1945

The Cromwell was the fastest British tank to serve in the Second World War , with a top (ungoverned) speed of 40 mph (64 km/h). However, this speed proved too much for even the Christie suspension and the engine was governed to give a top speed of 32 mph (51 km/h), which was still fast for its time. Thanks to its excellent engine power and Christie parentage the Cromwell was very agile on the battlefield. The dual purpose 75 mm main gun fired the same ammunition as the US 75 mm gun and therefore it had around the same HE and armour-piercing capabilities as the 75 mm equipped Sherman tank. The armour on the Cromwell ranged from 8 mm up to 76 mm thick overall. However, on all-welded vehicles built by BRCW Co. Ltd, the weight saved by the welding allowed for the fitting of appliqué armour plates on the nose, vertical drivers' plate and turret front, increasing the maximum thickness to 102 mm. These vehicles are identified by their War Department numbers carrying the suffix W, e.g. T121710W. This armour compared well with that of the Sherman, although the Cromwell did not share the Sherman’s sloped glacis plate. The Cromwell crews in North-West Europe succeeded in outflanking the heavier and more sluggish German tanks with superior speed, manoeuvrability and reliability. However, the Cromwell was still not a match for the best German armour and British tank design would go through another stage, the interim Comet tank, before developing the Centurion tank.

Combat service

Wounded German soldiers being ferried to an aid post on the hull of a Cromwell tank

The Centaur was chiefly used for training; only those in specialist roles saw action. The Close Support version of the Centaur with a 95 mm howitzer saw service in small numbers as part of the Royal Marine Armoured Support Group on D-Day and a number were used as the chassis for combat engineering vehicles, such as an armoured bulldozer.

The Sherman remained the most common tank in British and other Commonwealth armoured units in Europe. Cromwells were used as the main tank in the armoured brigades of only the 7th Armoured Division, although the Cromwell was used in the armoured reconnaissance regiments of the other British armoured divisions (Guards Armoured Division and 11th Armoured Division) in North-west Europe, because of its speed and relatively low profile.[9] The Cromwell, in turn, was succeeded by small numbers of the Comet tank, which was similar to the Cromwell, being based on it and shared some components but had a superior gun in the 77 mm gun (a version of the 17 pounder with different ammunition).[10]

The Cromwell was found to be very reliable with excellent speed and manoeuvrability, though it required more maintenance than the Sherman. In northern Europe, the Cromwell was used by Allied units of the 1st Polish Armoured Division (10th Mounted Rifle Regiment) and 1st Czechoslovak Armoured Brigade.[11] After the war, the Cromwell remained in British service, and saw service in the Korean War with the 7th Royal Tank Regiment and the 8th King's Royal Irish Hussars.

The Cromwell/Centaur had the distinction of being the first tank to go into service with the Greek Army during the re-formation following the Second World War. Fifty-two Centaur I tanks were donated early in 1946, during the opening stages of the Greek Civil War but they were kept in storage due to the lack of trained personnel. In 1947, the first Greek officers returned from training courses in the United Kingdom and training of tank crews began. The Centaur saw limited service in the civil war as in 1949 battles were fought on mountains. Centaurs formed the core of the Greek Armour Corps during the 1950s and were retired in 1962, having been replaced by US-built M47s. Finland used the Charioteer version of the Cromwell post war.

Operators

Czechoslovak soldiers on a Cromwell tank near Dunkerque in 1945.


Variants

Centaur IV with 95mm howitzer, Royal Marine Armoured Support Group, Normandy 13 June 1944

The modifications and developments of the Cromwell were classified under "Type" and "Mark". A single Mark could cover up to four Types and a Type up to six Marks making classification complex.[12]

The Types ran from A (the earliest Cavaliers, Centaurs and Cromwells) to F (a late model Cromwell with driver's side escape hatch).

A Cromwell Mk IV of the Welsh Guards displays its speed at Pickering in Yorkshire, 31 March 1944
Centaur I
First draft. Armed with the Royal Ordnance QF 6 pounder (57 mm) gun (with 64 rounds of ammunition). It was used only for training. 1,059 produced.
Centaur II
Mark I with wider tracks and no hull machine gun. Experimental only.
Centaur III
Centaur armed with the 75 mm ROQF Mk V gun. In 1943, most Centaur I were converted to IIIs, but a few remained as such. 233 produced.
Cromwell VI
Centaur IV
Centaur armed with a 95 mm howitzer (with 51 rounds of ammunition). This is the only version of the Centaur known to have seen combat, in service with the Royal Marines Armoured Support Group. The vehicles were fitted with wading gear to get them ashore. Trunking waterproofed the engine inlets and covers were fitted to the guns. 114 produced.[13]
Centaur, AA Mk I
Used a Crusader III, Anti-Aircraft Mk II turret fitted with twin 20 mm Polsten guns. Were originally deployed in Normandy, but withdrawn as unnecessary due to Allied air superiority. 95 were produced.
Centaur, AA Mk II
Used a Crusader III, AA Mk III turret with twin 20 mm Polsten AA guns.
Cromwell VIIw
Cromwell I
Exactly the same as the Centaur I, but using the Meteor engine. Only 357 produced due to the switch from the 6 pounder (57 mm) to the 75 mm gun.
Cromwell II
Increased track width and removal of the hull machine gun to increase stowage. None produced.
Cromwell III
Centaur I upgraded with Meteor V12 engine. Only ~ 200 produced due to scarcity of Centaur I's.
Cromwell IV
Centaur I or III upgraded with Meteor engine, or built as such. The most numerous variant with over 1,935 units produced.
Cromwell IVw
Meteor engine, and all welded hull
Cromwell Vw
Cromwell built from the start with the 75 mm gun and a welded instead of riveted hull, upgraded with additional armour (102 mm) to hull and turret front.
Cromwell VI
Cromwell armed with 95 mm howitzer. 341 produced.
Cromwell VII
Cromwell IV and V , fitted with Type F hull, wider (15.5 inch) tracks, and additional gearbox. These were introduced very late in the war and did not see much in the way of combat. ~ 1,500 produced, Some saw combat in the Korean War and many were later converted to the Charioteer self-propelled anti-tank gun.
Cromwell VIIw
Cromwell Vw reworked to Cromwell VII standard, or built as new to that standard
Cromwell VIII
Cromwell VI reworked with same upgrades as VII.

Vehicles based on chassis

Centaur Dozer with hydraulic operated blade
Tank, Cruiser, Challenger (A30)
The design combined a lengthened Cromwell chassis with widened superstructure to mount the 17-pounder gun in a new turret.
SP 17pdr, A30 (Avenger)
A version of the Challenger using a lighter open-topped turret.
Centaur Dozer
A Centaur with the turret removed and given a simple dozer blade operated by a winch. Since the winch passed over the top of the hull it was not possible to retain the turret. One of "Hobart's Funnies". 250 produced.
Centaur Observation Post (OP)
A Centaur with a dummy main gun, and extra radio communications.
Centaur Kangaroo
A Centaur with turret removed to make space for passengers. (Few produced)
Centaur Armoured Recovery Vehicle (ARV)
A Centaur with turret removed, and replaced with winch fitted instead, and an optional A-frame.
Cromwell Command
The main gun was removed and it carried one No. 19 (Low Power) and one No. 19 (High Power) Wireless sets. These were used by brigade and divisional headquarters.[14]
Cromwell Observation Post
Cromwell IV, Cromwell VI, or Cromwell VIII fitted with extra radio equipment; 2 x No. 19 and 2 x No. 38 (portable) radios. The main gun was retained.[14]
Cromwell Control
Two No. 19 Low Power radio. Main armament kept. Used by regimental headquarters[14]
Excelsior tank
experimental design with elements of Infantry tank as a possible replacement for Churchill tank
FV 4101 Charioteer
Cromwell hull with a QF 20 pounder gun in a tall turret, designed in the 1950s to give more fire support. 200 produced.

Surviving vehicles

Cromwell IV memorial to the 7th Armoured Division (Desert Rats) Ickburgh in Norfolk

Around 56 Centaur and Cromwell tanks survive, ranging from scrapyard wrecks to fully restored museum vehicles.

Cromwell tanks

Around 26 Cromwell tanks exist in various states.

Centaur tanks

Around 17 Centaurs and 9 Centaur Dozers exist in various states.

Other examples include:

See also

Tanks of comparable role, performance, and era

Notes

  1. ↑ The designation as the eighth Cruiser tank design, its name given for ease of reference and its General Staff specification number respectively.
  2. ↑ It is unclear if it was granted its own number or also referred to as the A24.

Notes

Citations
  1. ↑ WWII Vehicles
  2. 1 2 "The A27M Cromwell tank".
  3. ↑ Crawford, Steve. Tanks of World War II, pg. 46
  4. ↑ Fletcher The Great Tank Scandal pp. 65–66
  5. 1 2 "The Chieftain's Hatch: Exercise Dracula". world of tanks. 05/07/2014. Check date values in: |date= (help)
  6. ↑ User Manual
  7. ↑ Fletcher, p. 100
  8. ↑ Jentz, Thomas; Doyle, Hilary (1993). Tiger 1 Heavy Tank 1942-45. Osprey Publishing. p. 20. ISBN 1855323370.
  9. ↑ Bingham p. 28
  10. ↑ Bingham AFV Profile 25 pp. 34–35
  11. ↑ Bingham p. 30
  12. ↑ Cromwell Tank p.xiii
  13. ↑ Ness, Leland. Jane's World War Two Tanks and Fighting Vehicles. p. 22.
  14. 1 2 3 David Fletcher, Richard C. Harley, Peter Sarson. Cromwell Cruiser tank 1942–1950 (New Vanguard series). Osprey Publishing. p. 34.
  15. ↑ http://preservedtanks.com/Profile.aspx?UniqueID=1573
  16. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 http://the.shadock.free.fr/Surviving_Cruiser_Tanks.pdf
  17. ↑ "Desert Rat Walk". Forestry Commission. Retrieved 8 November 2010.
  18. ↑ "Cromwell Tank - Antwerpen". TracesOfWar. Retrieved 23 December 2014.
  19. ↑ http://preservedtanks.com/Profile.aspx?UniqueID=545
  20. ↑ "Benouville and St-Aubin-d'Arquenay". 1944 The Battle of Normandy The Memory. Normandie44lamemoire.com. Retrieved 2 October 2013.
  21. ↑ "Hermanville-s-M. and La Brèche d'Herm.". 1944 The Battle of Normandy The Memory. Normandie44lamemoire.com. Retrieved 2 October 2013.
  22. 1 2 http://www.dailymail.co.uk/news/article-1041825/Revealed-The-astonishing-D-Day-tanks-the-English-Channel.html
  23. 1 2 "Discovery in the Solent". FBBC. 28 July 2011. Retrieved 29 July 2011.
  24. ↑ http://hmvf.co.uk/forumvb/showthread.php?35747-Centaur-Gun-Tank-Ressurection!
  25. ↑ "Centaur Dozer Mark 1 (E1985.32)". The Tank Museum. Retrieved 2 October 2013.
  26. ↑ http://preservedtanks.com/Profile.aspx?UniqueID=2300
  27. ↑ http://preservedtanks.com/Profile.aspx?UniqueID=2310

References

External links

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