Wheeled War Vehith
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Vith a "Go-anywhere" .Performance Non Track-laying Machines Demonstrate their Remarkable Ability to Negoti-ate Very Difficult Terrain. A Triumph for Fourwheel Drive and Independent Suspension NE a surface consisting of innumerable smalland irregular . mounds of. Soil, each 2 ft. or 3 ft.
high. Here and there picture some larger mounds with an occasional small ravine and a .low-lying patch, .,wathrlogged. Not an ideal site for wheeled Vehicles! That, of course, was why it was chosen to demonstrate recently some of the remarkable qualities of a small fleet of Daimler armoured cars. Two types were represented 'by some half-dozen examples of each. The " Armoured Car, Daimler Mk. I," to quote its official title, and the " Car .Stout, Daimler II," are by no means the latest products of this famous company, but they have the merit Worn a journalistic viewpoint) of being no longer on the secret list. The former weighs about 74 tons and the latter some 3 tons, but each travels on four pneumatic tyres placed conventionally " One at each corner," ..
The engines, too, 'are virtually standard Daimler six-cvlindered jobs of 27 h.p. and 18 h.p. -.R.A.C. rating. with Fluid .Flywheels and preselector gearboxes. Thereabouts. the likeness to a peace-time vehicle ends.
• As may be gathered from the open, ing paragraph, the terrain was , quite the most impressive on which we have
yet seen L.Irty_demonstration of wheeled vehicles. Yet all these Daimlers clambered surely over it. Some drivers preferred a slOw-but-sure technique, whilst others tackled it at some speed and were equally sure.
Not one of these vehicles stopped from wheel-spin, or grounding, or any other involuntary cause.' All of them continued to make forward progress with one wheel in mid-air. • Later, there was an exhibition Of sheer wheel grip iri the ascent and, perhaps more difficult, the descent of a turfy hill with a gradient Of the 1-in-2 variety. Earlier, there had been shown the fine controllability of these ,. machines, forwards or backwards, on a sodden field.
In either. direction they could be comeMd sharply, .put into a broadside, if wished, and al easily pulled out of the slide again. When travelling forwards at some 40 m.p.h. they could be stopped promptly and taken aWay in reverse, with barely a stationary , pause; to accelerate rapidly to as high a speed backwards as was attained in the normal direction.
Two design • features are mainly responsible for the remarkable performance of these Daimlers. One is the transmission arrangement and the other is the suspension.
As to the transmission, the outstanding fact is that so-called " diagonal spin " cannot occur to these machines. They drive on all four wheels, of course. That is virtually standard practice for all heavy cross-country military vehicles, but there is more in the Daimler scheme than that.
If each driving axle has its own differential and the vehicle traverses uneven ground, Circumstances will eventually arise in which two diagonally opposite Wheels are on ground higher than that carrying the other two wheels. The latter, therefore, will be only lightly loaded, although subject to just the same driving torque as their mates. Consequently, they May spin, The Daimler arrangement has only one differential, placed amidships. From one side of it, power is taken to both wheels on that side of the vehicle, the other two wheels being • driven similarly from the other halt of the differential.
Thus, no wheel can spin unless the other wheel on the same side alsb-spins. As, short of actual grounding, no normal conditions can lift the lead from both wheels on one side at the. same time, this scheme results in the practical elimination of wheel-spin. • Admittedly, when • travelling along the side of a hill some weight is transferred from the upper wheels .tothe lower ones. This, however, is not a very practical argument against the Daimler scheme, particularly in view of the weight distribution of these vehicles. The smaller one can be tilted to 60 degrees and the larger to 50 degrees from the vertical without f:ausing it to -.capsize: Any usual inclination therefore ivill transfer very little 'weight from one side" to the other.
Turning to the -suspension system, each wheel is independent of the•other and has a remarkable range of movement. In the Armoured 'Car this, is, actually, 16 ins, and in the Scout it is half as much. Both types use heavy helical springs, with a comparatively low rate. These features undoubtedly account for the Daimler ability to deal with such highly irregular surfaces as those used for the demonstration.
A brief outline of the general design of both vehicles will be of interest. The engine of the Scout develops over 70 b.h.p. and, with Fluid Flywheel and five-speed epicyclic gearbox, is loCated at the back. It drives a central transfer box, which has a forward and reverse gear and a differential. All five ratios, therefore, are available in both directions of travel. From the differential, the driVe is taken to each side of the vehicle, as already stated.
A similar specification applies to the
Artnoured Car, except that its larger . engine develops .100 b.h.p., and an 'additional steering wheel, with certain other duplicated -controls, is plated at the back of the vehicle, so that the commander can take over without delay when it is necessary to drive the vehicle backwards quickly.
In this medel, too, there isan epicyclic reduction gear in each 'hub to relieve the main transmission components of the heavy torque 'required' at the wheels,. Ground clearance under the Armoured Cal' iS 16"ins.and
under the Scout is1Ojis.• From what has been written, it will be understood that both of these-machines were designed specifically for
their military purpose. This .was emphasized, after the demonstration, by Sir Bernard Docker, chairman of the company, who explained that the desire had been to provide, with -the least possible delay, somethingthat would he a real help to win the war, and without regard to its ' possible utility in peace-time.
Actually the -early history of -thig enterprise may sdrprise those who know how many years commonly elapsed in normal times between the initiation of a scheme and the prodl1Ction of the resulting model. The speed of ,the Daimler development is all the more remarkable when it is realized that this company had no background of experience with such vehicles as were proposed.
The following are the principal dates. After the preparation of preliminary schemes for consideration. hy the authorities, design work started in
June, 1988. Four months later, in October, the first vehicle took part in Army trials in Wales. By December of the same year, this same vehicle had" covered 10,000 miles on roads and across country in the hands of War Department testers, As a result, there were some detailed revisions, mainly to the armoured. hull, to improve the fighting efficiency. They added to the total" weight and thus necessitated more power and stronger suspension.
• In the middle of May, 1939, a small order was placed for the revised vehicle and the first batch was delivered to the Army in the _following December.: From then onwards production
was tontinhous. • • • • • This early success suggested a larger fighting yehicle • with a two-pounder gun-in a rotating turret; similar to 'the light Tanks of thelke .days. Design for this model started in April, 1939; and-. 'the first machine wasrunding by the' en,d of, the year. Testing. again led to' some re-Vision, -including a stronger, transmission system, and the first production vehicles of the final type "came
off the line in April; 1941. " In both cases, "encouragement and expert advice were given :by the authorities and, for the Armoured Car,
• Vickers. .Armstrongs, Ltd., supplied -drawings of an existing Tank turret' design.. Even so, the Daimler achieve-, melit was a; fine one .. and illustrates. again the inestimable value of the motor industry-to this Nation.