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SOME IDEAS FROM AMERICA.

26th August 1919, Page 14
26th August 1919
Page 14
Page 15
Page 14, 26th August 1919 — SOME IDEAS FROM AMERICA.
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AMERMAN designers of commercial motors seem to be indulging largely in their inventive genius, and some quite original ideas are the result. Whether all of the constructions exemplified will stand the test of time remains, of course,

to be seen. It should be borne in mind that the American " truck " industry, as they call it, is much younger than our own, and all mechanical Contrivances have at some time or. other to pus through witat is called the freak stage, which_ only really useful devices survive.

The idea of fitting springs between the main frame and engine sub-frame is not a new one. A chassis embodying this feature ivas described in this journal a year or so ago. In that case, ton, the 'design emanated from the States. We do not recollect, however, to have seen the idea carried so far as it is in the Forschler truck, in which the whole of the engine and transmission gear is carried on a separate Irani; independently sprung, the springs being applied direct to the vehicle axles. For this purpose, a light rectangular frame, built of channel section, is carried from the front axle upon a pair of double elliptic springs. To its rear is attached a pair of quarter ellipties, the rear ends of which are secured to shackles an the rear axle. The main frame is suspended in the usual' way on two pairs of semi-elliptics. The idea at the back of this arrangement is that in ordinary design the springing of a commercial vehicle is. more or less effective according to the load which it may be carrying. Ineffectiveness of the springing reflects upon the durability of

the power unit and transmission geae. With this special design, the mechanism of the chassis is uniformly sprung no matter what may be the paying load on the vehicle.

i'r7ire.other eha.ssis, the Old Hickory, a certain amount of interest attaches to the suspension of the radiator. A stiff channel, broad side up,"is bolted beneath the main frame. The base of the radiates.' is secured to this by studs, but prevented barn making actual contact by

means of coil springs. Tem pairs of springs are used in the assembly, one above and one below the cross member, and owing to a difference in their periodicity, vibration, it is claimed, is successfully damped out. Another feature of this chassis, one which we regard as of douhtful utility, is the regulation of the fan speed from the dash. Greater extremes of temperature are naturally encountered in the States than here, but to counteract this by varying the tension on the fan belt and causing it to slip in cold weather, which is the device adopted on this chassis, hardly seems expedient. Shackles are eliminated from the rear springs of this chassis. The forward ends are secured to 'brackets upon the frame, and the springs, apparently, serve as radius and torque rods. The rear ends slide within brackets of speeded design, and hear against wearing pieces of soft steel which are readily and cheaply renewable. Lubrication, as may be gathered by a glance at our illustration, is effected by a substantial grease cup. In order to avoid drilling the flanges of the frame for the rear spring brackets, and yet at the same time to provide means of securing these brackets in a manner which is essential having ire mind the important duties which they have to perform; special hook bolts are ved, which pass beneath the frame, take hold of the flange at its near edge, and are nutted up on the outside face of the bracket.

Cleanliness of appearance is certainly one feature of the Atlas internal-geardrive axle. The driving pinions, cressshaft and differential are arranged vertically above the -wheel centres instead of, as is usual, forward of them. This gives considerably more road clearance, as is apparent from the illustration, and aleo allows of more convenient layout of engine and gearbox, whilst at the same tithe maintaining the normal position of the propeller shaft in line with the rest of the transmission. The one-piece differential and cross-shaft ease also serves to carry the weight of the chassis, which

is a novel feature for this type of axle. We understand that. this axle is to be fitted to future models of the Alterbury ohassis, for which we believe Mann and Overton are the agents in this rouetry.

The worm drive jumped very quickly to favour in the States for commercial vehicles, in which characteristic the heavy vehicle over there differs markedly irons the touring car, wherein the worm and wheel as a final drive is practically non-existent. There are, however, -striking -signs that all is not as, it should he in this regard, for activity, at least as concerns the design of internal gear rear axles, is useticalarly strong. The Parker lias many ingenious features. Lie the 'first place, there is a very slight rerlue, don only in the bevel pair, practically all the ratio as between engine and rear wheel speed 'beingeffected in the in

. ternal gears. One natural consequence . of this is that the differential and driving axles are kept to a minimum as regards Weight and size. A strong. point has • been made of accessibility. It is claimed that the bulk of the mechanism can be diaserribled in a few minutes. The live

axles are withdrawn between the spokes a the road wheels through a specially provided opening in the driving gear casing.

The outstanding feature of this axle, however, is undoubtedly the brake. This is carried in the differential casing, and

is designed on the Same principle as e

multi-disc clutch. One set of dises carried on splines on a sleeve on the differential shafts. The other discs, alternating with these, are prevented from rotating by being _slotted so is to engage with projections on the inside of a stationary drum. The discs are pressed together by means of a sleeve fitting, loosely upon the differential shafts, and operated through special toggle gearing.

They are separated in an ingenious manner. Alternate discs are corrugated, so that as the pressure tending to force them together is released, the spring in the corrugated discs forces those on each side of it apart and away.

Lubrication is another interesting feature. The lubricant is lifted by the main internal gears from the bases of the casing on the rear wheels It is delivered into radial boles in the splined shaft, and the oil is drawn through these

A by centrifugal action through the spaces in the corrugated discs in the brake gear. It is thrown thence to the outside of the casing, draining back to the reservoir.

The axle is made in three sizes, for 2, 3i and 5-ton chassis, and may be arranged so that the cross shaft is either above or in front of the load-carrying axle, or it may be at some intermediate point between these two extreme positions.

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