STRIKING POINTS IN CHASSIS DESIGN,
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THERE is no doubt that a Show such as that now proceeding in Paris is of great value to British makers in that it provides a somewhat rare opportunity for making a comparison of points in design. Some of these do not appeal to what we may term the British temperament in motor vehicle construction,
but many have an interesting spice of novelty, and in most cases are remarkably neat; we therefore devote a fair amount of space to this feature. Not all the points to which we refer are new, but where old methods have been modified or have proved particularly satisfactory they are dealt with.
A somewhat unusual construction is to be found on the S.P.A. ; in the larger model the transmission brake shoes are anchored to a well-gusseted crossmember, and to the other side of this is fastened the large Pork end of the torque tube, the universal joint of the propeller shaft being carried between the arms of the fork. This model has Westinghouse vacuum-operated brakes. The smaller type has the torque-tube
ball anchored to short extension arms on the gearbox, the loco.-type brake being carried between ball housing and gearbox.
In the 2i-ton Cottin et Desgouttes the propeller shaft is divided and provided with a centre bearing and cardan joint enclosed in a large aluminium case. The rear axle is of the double-reduction type with spur and bevel gearing.
A particularly neat axle is to he seen on the La Lieorne. This has a cast centre with a large inspection plate practically covering the rear and tubes of almost oval section bolted on; this shape gives great strength in the vertical plane.
A combination of double-reduction and dual-type axles is used en the DonnetZedel; the gearing is carried by a double-banjo load-bearing member, and the drive conveyed by enclosed shafts to rack-and-pinion gears in the wheels. Another curious feature in this chassis lies in the propeller shaft, which is in halves, bolted together at the centre, but with no support bearing—presum ably, it facilitates dismantling. .
Wood wheels are still to be found on a; few of the heavy chassis, and included amongst these is the 10-ton Dewald. Recent tests have proved the great superiority of the wood type from the point of view of shock absorption, and this vehicle is designed to carry deadweight in the shape of blocks of stone..
On one of the. medium-sized De Dion chassis the bearing for the rear end of the cardan shaft is supported by a double-banjo .cross-member ; the housing is of a gimbal type, and itself carries the forward end of the torque tube. The hand-brake connections are of curious construction; the lever rocks two crossbars, each of which has one end supported in ball sockets on the frame side-member, and the other connected, through a fork-and-pin cardan joint; to a lever mounted on the front end of the torque tube. Some of the De Dion engines have the fan mounted on the dynamo shaft, both being driven together by a link belt.
Some of the largest Hardy disc joints which are used for commercial vehicles are employed on the heaviest Bet.Bet chassis. Any risk of tearing at the bolt holes is prevented by the use of toothed locking plates under bolt heads and nuts.
Headlamps with two bulbs, to give high and low candle-power, are to be found on a large number of vehicles. Much interest centres in the new 1-ton Fiat chassis, which is shown for the first time. So far as engine and gearbox are concerned, these follow on the lines of the 8-cwt. type, the chief addition being a remarkably neat axle with overhead-worm drive.
The chassis has been simplified almost to the last, degree iii the endeavour to obtain competitive manufacturing cost. The poiver unit is an L-type monobIoC, with detachable:head croSs drive to magneto and centrifugal pump, a directdriven dynamo and a link belt for the fan. Power starting is also -.provided.
Unit construction is employed for engineand gearbox, and fourspeeds are permitted.
The change-speed lever sleeve slides over the brake cross-shaft, and on the latter is mounted a right and left-handthreaded adjuster, which tightens the operating cable. Hardy joints are used on the tubular propeller shaft. The frame is inswept to the front and tapered at each end. Petrol is carried in a dash tank with the filler inside the bonnet. The wheels are Michelin discs carrying twin tyres at the rear.
Underslung rear springs are used on the chain-driven Aries, and above each is a five-leaved buffer spring of almost equal length.
The E. Bernard 2-ton chassis was also shown last year ; it has a fine example of the bevel-and-spur double-reduction axle, use being made of a particularly clean double-banjo casing, belled at the ends to carry the wheel bearings and brake gear. There is also a long torque tube, which is divided at the celitre and provided at this point with a ball bearing, which prevents whip occurring in the propeller shaft; this construction is most unusual. We also noted that the front end of the torque tube is carried on the propeller shaft-a practice which is now being followed by several makers.
On the Salmson is an unusual form of rear suspension, quarter-elliptic springs reach back to the axle, and supplementary three-leaved flat springs stretch forward from rearward extensions of the frame side-members. Long plunger-type pneumatic shock absorbers are also used.
Most S.C.E.M.I.A. chassis such as that employed on the big Paris bus, C33
have dual type axles, but the latest type, as used for .express buses' has a neat double-reduction gear in a double' banjo axle casing.
We referred a little way back to a combination of fan and dynamo drives; this method is also employed on the light Unics, but here the dynamo pulley is at the back, and the two-bladed fan is driven through the armature spindle. In the *ton Unic the rear axle is of the bevel-and-spur double-reduction type, and the main point is that the double-banjo casing is built up instead of being in one piece.
Better road contact for the twin rear tyres is the object achieved in the curious axle adopted on the 4-ton Delahaye. At first sight the drive appears to be by worm, but actually the place of the worm is taken by a skew-gear, the teeth of which are set at a very slight angle; this drives a layshaft, which is slightly out of the straight, and provided with bevel gears for driving the wheel driving shafts, each of which drops a few degrees from the horizontal. A differ ential gear is, of course, incorporated. A simple form of servo motor for obtaining more powerful operation of the brakes is embodied in all Renault chassis for loads of 3 tons to 7 tons. A worm on the mainshaft of the gearbox drives a cross-shaft, on which is mounted a friction clutch, brought into action by the brake pedal, and a chain is used as the medium between this gear and a long lever commanding the brakes.
Another and fairly well-known Renault device is the neat epicyclic reduction gear contained in the rear wheels of the 6-ton and 7-ton machines. This method reduces the size of the whole axle, and considerably reduces the stresses on the axle shafts.
Noshow would be complete without its Ford conversion sets and of these there are several, one in particular consists of a Ford chassis lengthened by inserting an aluminium extension piece between the transmission easing and a cross-member supporting the torquetube ball.