S.L.M.
Page 32
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MHE • exhibits on this stand are of
exceptionally interesting character, owing to the fact that a very low frame level has been obtained with the assistance of a front-wheel drive system. This arrahgement leads to considerable overhang at the front end, owing to the fact that the gearbox, from which the drive is taken to the front Wheels, ig placed behind the engine, but this overhang is in itself an advantage for bus work, as it permits of the provision of a very adequate lifeguard.
A very interesting feature of the chassis is found in the fact that the constant-mesh gears in the gearbox are selected by a series of internal-expanding hydraulically operated clutch. Oil is supplied to the gear shafts under pressure, and its distribution is easily controlled by a valve operated by a quadrant gear lever on the steering column, movements of which result ;n oil pressure expanding the appropriate clutch, and thereby selecting the desired gear ; this system works very well in practice, gear-changing calling for no particular skill on the part of the driver.
The method of front-wheel driving should be closely examined, as this is designed on highly efficient and practical lines, from each side of the gearbox cardin shafts extend to housings mounted above each stub axle; here a pair of bevel gears transmits the drive to a vertical shaft running through the hollow stub axle and terminating in another bevel pinion at the bottom. This last-named pinion meshes with a large ring gear secured to the front wheel and turning therewith when the vehicle is steered ; in °that words, the ring gears roll round the bevel pinia to accommodate steering movement. Thanks to these"driving arrangements, there is no running mechanism whatever to the rear of the driver's sPat, with the exception of the rods and levers controlling the large rear-wheel brakes. The front axle is of I section and the long semi-elliptic front springs are underslung.
The frame is cranked downwards just behind the gearbox unit, and thereafter takes a straight line to the tail end. The rear axle is dropped at the centre, near the frame, and simply carries the semi-elliptic springs, yearwheel bearings and brake tear, the simplicity of the assembly being, of coursi due to the fact that the driver is taken through the front wheels. • The two vehicles exhibited comprIse a chassis with a driver's cab, and a • 2-ton lorry which gives an excellent idea of the advantages of the low-loading level ; the latter is fitted with a front lifeguard. In addition to these exhibits, a compete gearbox unit is on view, from which the novel mechanism employed can be clearly seen ; likewise the powerful brake which acts upon the transverse shaft coupled to the cardan shafts, and therefore takes effect upon the front wheels.
Incidentally, the front-drive arrangements of the 2-ton lorry differ sonmwhat from those employed on the chassis, each cardan shaft in this case being provided with a massive universal joint above and in line with the steering pivot, which permits of steering movements. From this joint the drive is simply conveyed through a short shaft and pinion to a large gearwheel bolted to the front wheel. In other respects the two chassis are very similar ; in each ease the engine is of the orthodox few-cylinder type with the cylinders cast in pairs. Modern Wheel Drive, Ltd., 17, Victoria Street, London, S.W.1.