Timber Tractor to Work at 8,000 ft.
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FOUR-WHEEL-DRIVE forestry tractors adapted for tropical working at altitudes up to 8.000 ft. in the Mount Kilimanjaro region, are being constructed by Universal Power Drives, Ltd., Pcrivale, Middx. The vehicles are to the specification of the Utilization Officer, Moshi, Tanganyika, who required a tractor capable of working on 1-in-5 gradients, on or off the road, with a maximum road speed of at least 30 m.p.h. under load, to be able to do heavy work at 6,0007,000-ft. altitudes, with occasional working below 4,000 ft., and to have a detachable jib of 2-ton capacity.
The new units arc basically similar to the Unipower Hannibal timber tractors, with which most of the components are interchangeable. It is a normal-control model, seating five persons including the driver.
The Gardner 5LW oil engine which in standard form develops 94 b.h.p. is set to give 72.5 b.h.p. at 1,700 r.p.m. for high-altitude operation. Complete dust-proofing has been applied to the engine, which has three fuel filters and a Gardner oil-bath air-cleaner. Cooling is provided by a copper-tube radiator, centrifugal pump and 18-in. fan.
10 Forward Speeds
A 14-in.-diameter single-dry-plate centrifugally assisted clutch transmits the drive to the five-speed main gear , box, which, used in conjunction with the two-ratio transfer box, provides 10 forward and two reverse ratios. The transfer box includes a drive to the winch, which thus has five forward speeds and a reverse. Engine, clutch and gearboxes are mounted in the chassis frame as a unit, the main gearbox casing forming a cross-member of extreme rigidity.
The front and rear fully floating axles are of 5-ton capacity and are driven by propeller shafts with HardySpicer needle-roller universal joints. The one-piece axle casings have banjo htusings to accommodate the 5.571 to el4 1 ratio spiral-bevel final drives. 1he drive to the front wheels is transferred through Rzeppa constant-velocity highangle joints. The steering box is a heavy-duty Marks cam-and-roller type.
The braking is by rodand cableoperated Girl ing two-leading-shoe units on all wheels, with a Clayton Dewandre servo, and couplings are fitted for trailer-brake attachments. A large vacuum tank is placed beneath the instrument panel. The hand brake is effective on the rear wheels only, and a hand trailer-brake control is also provided.
Semi-elliptic springs 45 in. long are fitted at the front, those at the rear being 50 in. long. The frame has thick channel-section side members, with 3-in, flanges and a maximum depth of 12 in., and all cross-members and spring brackets are bolted.
The winch is mounted on a subframe with the land anchor, thus keeping all shearing stresses off the main chassis frame. The I 1-in.diameter drum is supplied with 300 ft. of 11/16-in, cable and is carried on a 4-in.diameter shaft.
A brake is provided on the transmission as well as on the drum itself, both being actuated by one lever from the driving position, but the drum brake is separately applicable from the rear of the tractor. Roller guides are arranged for rear and forward winch ing and jib operation, and the winch can exert a straight pull of 62,000 lb.
The jib is of tubular construction, with a maximum capacity of 2 tons, and can be dismantled and carried on brackets situated above the near-side front wing. Use of the jib dispenses with the need for a logging arch and can facilitate loading.
Because of the rugged nature of the country in which these tractors will be operating, all vital auxiliary equipment is, as far as possible, kept within the chassis frame and exposed parts are made exceedingly tough. A full-width brush guard is attached to the front bumper.
Front Axle Protected ' The front axle is protected by a robust shield which has the effect of lifting the front of the tractor when any obstruction . is encountered, thus enabling it to be reversed away without having damaged the axle.
A steel toolbox is located above the transversely mounted 45-gallon fuel tank and provision is made for stowing two spare wheels on top of the rear wings.
The tractor is 8 ft. wide and 17 ft. 8 in. long, the wheelbase being 8 ft.
10i in. In road condition it weighs 5 tons 6 cwt., this being equally distributed between the front and rear axles. All wheels carry 12.00-20 tyres.