WW II, a British focus  



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Preliminary Report No. 12



School of Tank Technology

May 1943


The car arrived in this country in good condition. This is accounted for by the comparatively small mileage covered, and by the considerable trouble taken to protect components from corrosion or damage during transit. After a few minor adjustments the car was made a runner, and mechanically it appeared to be fairly sound with the exception of the steering which needs some attention. Our observations on the performance are in no way intended to constitute a field trial as this is to be carried out by F.V.P.E. at a later date. However, as the result of a brief run, a few observations with regard to the handling and performance of the car are given later in this foreword.

Mechanically the car has many interesting and certain commendable features. The distributed drive to all four wheels and the four wheel steering, make it possible to use a single differential at the expense however of a very large number of bevel gears. The effect of variations in angular velocity of the wheel, due to the cross-pin type universal joint, is very considerably minimised by the hub reduction gear, and further by the four wheel steering which allows a reasonable turning circle to be obtained with a small angular wheel movement. If one can assume that this arrangement is satisfactory, the absence of four constant velocity universal joints constitutes a very considerable economy in manufacture. The five speed gearbox and overdrive gear, giving six forward speeds, gives a wider range than is usual in Armoured Car practice. A directional control lever reverses the whole transmission and allows the rear driver to use the first four speeds. Thus the car may be driven in either direction.

The wheels are not easily removable but detachable rims are fitted. Two spare rims are carried on either side of the hull and are mounted on hubs which are free to revolve. The tyres on the spare rims are therefore able to take the weight of the car to avoid bellying over very rough country.

Of the engine very little can be said, as in the interests of time, and in view of the forthcoming running trials it was not considered advisable to dismantle this unit. Externally it appears to be fairly orthodox and the estimated power given on page 11 should be taken as being very approximate, as neither the capacity nor speed range are Known. Access to the engine is difficult, and the tubular chassis cross member which passes over it would appear to be decidedly inconvenient when removing or replacing the unit.

While the general mechanical layout appears to have been well thought out and designed specifically for the job, the mechanical details in certain cases contrast strikingly in their inadequacy or shoddiness. The whole construction and layout of the rear driver's section savours of modification or after-thought. The main petrol tank under the floor is only protected by a light gauge tray and is extremely inaccessible. The forward tank feeds into the main tank by gravity and no stop cock is provided in the line. There are other similar examples of bad design.

The electrical equipment is generally of good quality. The inter-communication equipment appears to be an aircraft installation, the various units being marked "REGIA AERONAUTICA." The dynamo seems to be much smaller than would be required for the size of batteries carried, and may not be the original. No fuses could be found and it is assumed that the circuits are unprotected, which is rather surprising.

With regard to the armament and armour, it is noticeable that again the lack of attention paid to detail design considerably reduces the potency of the car as a fighting vehicle. The one man turret does not conform to the latest British requirement for a three man turret. The exposed traverse gears, the awkward position of the 2 cm. cocking handle and the limited observation in the turret are in our opinion decidedly undesirable features. There is no electrical equipment in the turret and consequently no rotary base junction. The commander is therefore faced with the problem of what to do with his headphone and microphone leads when traversing the turret.

It is impossible to sight the rear hull gun when it is fully depressed and extremely difficult to do so at any angle under zero. The gunners seat is not in line with the gun and he must lean awkwardly in order to sight when the gun is traversed left. His back is fouled by the turret gunners seat when the turret is straight ahead or traversed left. These points and the improvised appearance of the gun mounting suggest the possibility that the rear hull gun was added as an afterthought. The wooden ammunition racks are very roughly constructed. In general, splash protection is noticeable by its absence. A desirable feature on the other hand is the clean belly of the car and for this reason it is thought that its ability to cross wire obstacles may be good.

As the result of a brief cross country and road run the following points were noted with regard to the handling and performance. Owing to the defective steering which caused very severe "shimmying" at speeds over about 20 m.p.h. it was not possible to drive above this speed.

The engine pulled fairly well at slow speeds and from the front driving position was mechanically quiet especially in view off the fact that no bulkhead is fitted. Engine fumes were barely noticeable in the fighting compartment when driving forward, but were decidedly objectionable when in rear control. There did not appear to be any tendency for the engine to overheat in rear control although very little running was done in this direction.

The first four gears are noisy and the change is extremely slow. The absence of a clutch stop makes upward changes on rising ground difficult. The direct and overdrive gears, fifth and sixth, being of constant mesh, are much quieter and the change is, of course, is much quicker. The change from front to rear control is simple to effect from the front driving position and if the normal gear lever is in neutral, the clutch need not be used. From the rear driving position, however, the directional control lever is so situated that it is almost impossible to operate it.

At low speeds the steering was reasonably light by virtue of the fact that it is extremely low geared. As there is absolutely no self-centring action when driving in either direction, it is assumed that there is no castor angle. At about 15 mph there was a tendency to "shimmying" which increased in violence unit at about 20 m.p.h. the car was almost uncontrollable. It is considered that, although this defect is obviously an abnormal state of affairs, the apparent lack of castor angle may aggravate this tendency.

The hydraulic brakes were quite light to operate, but not very positive.

The independent suspension was excellent over both road and cross country and although extremely soft it did not appear to cause any undue degree of rolling or pitching at the fairly slow speeds which were attained.

The front driving position is quite comfortable, but the rear driving position is impossibly cramped for a tall man. The lack of any side vision is a decided disadvantage.

The car was driven into a small muddy depression of clay and became completely bogged even though the differential was locked. There was no question of clutch slip or of insufficient engine power as all four wheels were turning. It is not considered that most other four wheel drive vehicles would have become bogged under similar conditions, and the fact that the car was shod with comparatively smooth "Libia" tyres may have been partly responsible for this rather surprising failure.

In conclusion it may be said that the general impression is that the basic design has been well thought out with a view to producing a manoeuvrable high speed fighting vehicle, but that certain detail design features particularly with regard to the fighting arrangements have received such scant attention that the potential possibilities have not been fully realised.