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A21 Infantry Support Tank - A British StuG Story

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tankmodeler:

--- Quote from: apophenia on April 03, 2020, 12:04:35 PM ---On the radiators, I've read conflicting reports. Some sources say that they were successfully targeted by German 3.7 cm Pak 36s. Others claim that the louvres offered protection equivalent to 60 mm of armour plate. But which version is correct?
--- End quote ---
I've seen a number of dead Char Bs with holes in the louvres. The louvre itself was relatively thick, but there was a reasonable path from it through to the radiator for splinters and high velocity remnants making the radiators quite vulnerable.


--- Quote ---Another curiosity is the appareil Naeder at the stern which was almost as long the Renault engine. So, first chance I got, that hydrostatic system got junked. My British HO12 engine would need to be mounted fairly high up to meet its new transmission. I had a vague notion that this boxer engine could sit above a fuel tank ... not sure if that's ever been done or even if it would be practical.  ???

--- End quote ---
If the breech can be raised up enough that you can junk the French precision tranny, that is a key improvement, for sure. Using the later German experience, if you can manage +-15 deg traverse from the longitudinal axis, you are probably viable as a panzerjaeger.

By junking the tranny and simplifying the rear end you probably gain at least the capability to repackage things to bring the radiator trunking inboard and put the intake and exhaust up on the engine deck even if the radiators themselves are in about the same place in the sponsons.

Paul

robunos:

Interesting stuff !! 
Apposite, too, as A, I'm currently building the Matchbox Char B for a GB on another Forum, and B, I've been working on some Early / Mid-War British AFV Whiffery myself . . . more in due course . . .


cheers,
Robin.

apophenia:
Paul: Many thanks for those details! I hadn't thought of leaving the radiators where they were and just moving the trunking. Good thinking  :smiley:

Robin: Cheers. Hopefully, the next post provides some more grist for your mill ...

Alaric VI - A21 meets A12 'Matilda Senior'

Obviously, the calamitous fall of France ended the supply of French-made suspension parts for the Alaric programme. By June 1940, Dr. Merritt had already issued specifications for a replacement design - the A22 Infantry Tank (which would also eclipse the now-obsolete A20). But, as German troops lined the English Channel, the A22 was at least a year away from production. With an invasion threat building, it was critical that partially-completed Alarics be finished. An ad hoc solution was fitting Alaric hulls with the suspension of the pending A12 Infantry Tank - the so-called 'Matilda Senior'. The A12 was a Matilda I replacement but with an astonishingly thick armour. The result was a mass of 25 tons - just 2.5 tons short of the Alaric. Work began at once on adapting the A12's coil-spring suspension to the larger A21 hull.

Fortunately, production of the A12 suspension was well ahead of anticipated delivery to the tank's complex and largely cast hulls. Beyond the usual drive sprocket and idler, the suspension for the 'Matilda Senior' consisted of five paired bogie assemblies and a forward 'jockey wheel' which came into contact with the ground only when the bogie wheels were under load. Although the Alaric hull was longer than the A12, there was not sufficient space to install an additional bogie pair. Instead, a rear jockey wheel was added to each side. This 'fix' got Alaric assembly rolling again but the A12 suspension was somewhat overtaxed by the Support Tank's greater weight. In light of the times, this compromise was considered fully acceptable.

Top An Alaric VI prototype fitted with A12 'Matilda Senior' suspension units. This vehicle was part of the Dorset coastal defence force based at Lulworth in July 1940. The tank was actually assigned to the 52nd Training Regiment, Armoured Fighting Vehicles School - specifically, the Gunnery School at Lulworth, close to the Dorset coast.

The Alaric VI prototype's commander was A/Maj E.F. Offord (a South African who was an Assistant Instructor at the Gunnery School). Here, Acting Major Offord sits in his commander's hatch with access to a pintle-mounted Lewis gun. Since arriving at Lulworth, this Alaric VI has been fitted with an experimental 'pepper-pot' muzzle brake (likely to trial the effects of large numbers of firings).

Note the truncated, Alaric IIA-style cooling louvres (explaining why the tank's rooftop cooling 'mushroom' is fixed in the fully-open position). This prototype has a non-standard wireless arrangement and is also missing its lower suspension-covering skirts. For security reasons, the individual vehicle number has been painted out (although why that was thought necessary is unclear). It seems that this tank never received an individual vehicle name (which was not that strange for a prototype).

Into Active Service - the Operational Alaric VIA Infantry Support Tank

Two Alaric VI prototype conversions [1] were completed and both suffered cooling problems. The production model Alaric VIA introduced enlarged hull-side cooling louvres to address the issue. The extended louvres helped but - especially in Summer months - it was not unusual to see Alaric VIAs with their hull-top cooling 'mushrooms' gaping. Other than its suspension and cooling 'mods', the VIA was indistinguishable from the preceding Alaric V.

A total of 32 Alaric VIAs were completed and all were issued to the 141st Battalion, RAC (making up three squadrons of this newly-formed unit). [2] The Alaric VIA did what was required of it during the Summer of 1940. As feared, the under-strength suspension proved to be the Achille's heel of the  Alaric VIAs. Within a year, the type had been withdrawn from active service (other than some retained for crew training at Bovington).

Bottom An Alaric VIA of the 141st Bn, RAC, near Folkestone, Kent, in August 1940. This is a near-new vehicle. Note the Alaric VIA's enlarged cooling louvres and full lower skirts. A3864 has been fitted with a fixed machine gun shield armed with a Lewis gun.

(To be continued ...)

_______________________________

[1] The first Alaric VI prototype conversion was made to an Alaric I - one of the original French Char B1s supplied as demonstrators. In May 1940, this vehicle had suffered a failure of its Naeder hydrostatic system and was awaiting a replacement from France. (The other three Alaric Is went overseas with the British Expeditionary Force as support vehicles for the Alaric IA force. All three deployed Alaric Is were lost in France.) In June 1940, the remaining Alaric I had been stripped of its suspension in order to complete another Alaric IIA hull.

[2] 141 Bn formed as the 7th Battalion, Buffs (Royal East Kent Regiment) which was to be assigned to the 209th Independent Infantry Brigade (Home). Instead, the nascent unit was transferred to the Royal Armoured Corps. Members of 141 Regt wore The Buffs' cap badge on their black RAC berets (as did all such transformed former infantry regiments).

apophenia:
An Adversarial Relationship - DTD/MEE and the A23 Adversary

Other than some experimental conversion test-beds, the Alaric VIA was the end of the line for the Char B-based A21 series. However, it is also worth mention one further vehicle type - albeit, one with only a conceptual relationship to the A21. When seeking out suspension units with which to complete the unfinished Alaric V hulls, brief consideration was given to the vertical volute spring suspension (VVSS) of the then-experimental American M2 Medium Tank.

The reason for interest in the M2 suspension sprang from plans to build a new cruiser tank in Canada to British standards but based upon the M2 hull. For study purposes, an incomplete set of M2 drivetrain components was procured from the US Army's Rock Island Arsenal in late 1939. After examination by the Mechanisation Experimental Establishment (MEE) at Farnborough, the trial components were turned over to Dr. Merritt's Design Department at the Royal Arsenal, Woolwich. Although rejected as insufficiently strong for the Alaric, the VVSS units prompted the detail design of a lighter-weight future Tank, Infantry Support (a concept already being advanced by the Mechanisation Board).

As a 'clean sheet' design, the new vehicle could better represent the vision of the Mechanisation Board. This meant an 'assault focus' - defined as being well-armoured enough for head-on attacks against dug in positions including bunkers. The fighting compartment was designed around the '3-inch-36' gun. The gunner was ideally placed on the portside of the gun (with the vehicle's driver located on the vehicle's starboard side). Suspension units would be common with those of the forthcoming Canadian-made cruiser tank but propulsion would be by the Mechanisation Board's preferred high-speed diesel engine. Indeed, the diesel powerplant was one of the reasons that the vehicle's size could be greatly reduced compared with the Alaric series.

The engine chosen for what became the A23 Mk II Adversary, [1] was a 420 hp HLW D.4-5M 4-cylinder high-speed diesel. This prototype engine was made by the Hawthorn-Leslie-Werkspoor Diesel Engine Works (HLW Diesel) division of R. and W. Hawthorn, Leslie and Company of St. Peter's, Newcastle-upon-Tyne. The form of the engine was unusual for diesel engines of its time. In layout, the D.4-5M was a compact V-6 engine with cylinder rows arranged in a 30° Vee. On the centreline between the two banks of cylinders were an air compressor (in front) on centreline and, a scavenger pump (towards the rear). The end result was a very tall engine but one that was otherwise quite compact. [2]

The Adversary began as a cooperative project between the Woolwich Design Department and W.G. Allen & Sons. However, prototype construction was actually undertaken in works rented from another Tipton engineering firm, Horseley Bridge and Thomas Piggott. Considering the times, work proceeded quite quickly with the armed prototype A23 Mk II running under its own power by early September 1940. Problems were revealed immediately with the powerplant. [3] Since both David Brown transaxle and HLW Diesel engine were effectively prototypes themselves, teething troubles were expected. However, such were the exigencies of the Summer of 1940 that little engineering effort could be spared to work out the bugs. The prototype Adversary would later be used to test the 2.24 inch tank gun [4] but no further A23 Mk IIs would be built.

Our American Cousins - The US Grant Infantry Support Tank

After work on the A23 Mk II Adversary was abandoned, design attention turned to an Alaric replacement based directly on pending US M3 Medium Tank hull. Since the story of the Grant tank and its infantry support variant are well-known, they won't be described in detail here. The Grant Infantry Support Tank (GIST) was created specifically to address British requirements for an A21 Alaric replacement. Due to its urgency, the GIST was little more than a turretless Grant. However, that proved not to a major disadvantage since GISTs were generally operated in mixed formations with turreted Grants.

Bottom Grant Infantry Support Tank, 3rd Tank Regiment, Battle of Gazala, Cyrenaica, 27 May 1941. T20046 was a Pullman Standard-built GIST of the 3rd Tank Regiment during the Battle of Gazala. This GIST was abandoned when it hit a landmine at Bur el Harma on 27 May 1941.

Although the lack of a rotating turret could be critical, tactically, the GIST did have some major advantages in desert fighting. Obviously its profile was lower than that of the turreted Grant. The resulting weight reduction meant less ground pressure, giving the GIST superior mobility on dry, loose sand. More important still was simple availability. In the absense of any other infantry support tank, the Grant Infantry Support Tank proved vital to the Western Desert war.

(To be continued ...)

____________________________

[1] The unbuilt A23 Mk I was unrelated to the Adversary, being a projected lightened version of A21 Alaric VI. Quite rightly, the latter type was judged to be past its time for further development. Funds set aside for the aborted Mk I were reallocated towards the entirely different A23 Mk II Adversary.

[2] Two potential engine candidates were rejected - both lengthier inline diesels. One was the 420 hp 'Economy' inline 4-cylinder high-speed diesel submitted by William Doxford and Son (with a central scavenge pump dividing pairs of cylinders). The other was a more developed 6-cylinder diesel by North British Diesel Engine Works (NBDEW) - the LB-6M or 'Long Bore 6-cylinder, Military' -  based on a simplified cylinder design by engineer, J.C.M. MacLagan. In part, British Army technical people found difficulties in dealing with engine making firms with exclusively maritime backgrounds.

[3] Wags at Bovington would joke that the Adversary's diesel engine provided its own smokescreen - whether required or not.

[4] The 2.24 inch gun was another adaptation of ex-US M1897A2/M1897A4 tubes. In this case, worn barrels were bored out and a liner inserted. This liner and a 2 foot barrel extension were bored to 57 mm to take a new 'wildcat' round - necking down the US 75 mm casing to accept a driving band for a projectile from the pending Ordnance QF 6-pounder anti-tank gun.

robunos:
Again, good stuff, and another mention of my town . . .   ;D
I've read somewhere,but of course can't find it now, that some M3s were operated without their top turrets, to allow them to fit it into LSTs, so I'm thinking the Sicily campaign . . .


cheers,
Robin.

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