A LORRY WITH REAR-TRACK DRIVE.
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Details of the Novel Maccar
WITH the object of meeting the requirements of building contractors who are frequently called upon to leave the roads and to transport loads of material across very rough or loose ground on which it is almost impossible for the rear road wheels of an ordinary four-wheeled truck to secure a grip, the Mecca'. Corporation, of Scranton, Pa., U.S.A., has recently introduced a halftrack vehicle known as the " SureTrac " for gross loads, that is including the body, ranging from 5 tons to 5i tons.
So far as the general lay-out of the chassis is concerned, this follows what may be regarded as standard lines. The motive power is supplied by a fourcylindered engine of 40 h.p. rating, baying a bore and stroke of 5 ins. by 6 ins. respectively. 'T'o facilitate engine starting an impulse device is provided to work in conjunction with the hightension magneto.
The clutch is of the multiple-dry-disc type, whilst the gearbox is designed to give four speeds and a reverse. A spur reduction gear is also provided in conjunction with the gearbox, so that altogether eight forward and two reverse speeds are available. The propeller shaft is provided with universal joints at both front and rear ends, and the final transmission to the rear axle is by worm gear, which, together with the differential gear, is so mounted that it can be removed from the chassis as a distinct unit.
Principal interest in the vehicle lie-s in the half-track arrangement, at the rear, for which it is claimed that not only can the vehicle be used on ordinary roads with legs damage thereto than that caused by ordinary heavy trucks, but that it can be driven in and out of excavations and other places inaccessible to the usual four-wheeler.
No information is available as to the
exact details of the arrangement, hot both pairs of rear wheels are made in the form of steel pulleys around which pass stout endless bands of rubber, the outer surfaces of which are provided with non-skid treads. The hindmost pair of wheels or pulleys rotates on tapered roller bearings mounted on the ends of a built-up dead axle, which latter is pivotally and spring-supponted on the casing of the driving axle in such a way that whilst the distance between the two axles is always maintained, they can, when the vehicle is passing over rough ground, rise and fall in relation to each other. The cast-steel front wheels are shod with 36-in. by 6-in, solid tyres. Any type of body can, of course, be fitted to the chassis, the one illustrated being a contractor's tipper.