A Track-laying Tractor for Oilfield Operation
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Brief Details of the Outstanding Features of an Interesting Garrett -Gardner Six speed Machine that Has Been Specially Constructed for Working Under Conditions of Deep Mud or Thick Dust
IN the Mexican oilfields the condition Iof the surface varies from deep dust in the dry season to a morass of mud during the rainy season, but work has ta go on just the same. These, in brief, were the basic factors to be considered in the design of a tractor for the Eagle Oil and Shipping Co., Ltd. The machine selected was a multi-speed track-layer built by the Richard Garrett Engineering Works, Ltd., of Leiston, with special features suited to the widely varying conditions. In the issue of The Commercial Motor dated October 6, 1933, we described the model in question, so that it will suffice here to recall the outline of the design.
A Gardner 4 L2 (50 b.h.p. at 1,300 r.p.m.) oil engine, carried in a threepoint-suspended sub-frame, drives, through a Borg and Beck clutch, a three-speed-and-reverse gearbox ; next is a two-speed set, wish gear drive to the live sprockets at the forward ends of the two all-metal-track assemblies. The driver occupies a platform at the
front, and behind him are the fuel-tank, engine compartment and radiator; the last-named is well out of the way of damage when forcing a passage through dense undergrowth or tall grass.
The particular machine to which we refer has tracks of 10 ins, width in place of the standard Th. ins. Man; ganese steel shoes are fitted with i-in. diameter pins; no lubrication is needed. Labyrinth seals are employed in the bearings of the plain steel track idler wheels, of which there are four per track, each pair working in a pivoted and sprung rocker frame. This system ensures that the track at all times follows the ground contour. The standard system of rubber-tyred idlers is not used in this case.
To cope with the dust problem the engine is totally enclosed by steel bulkheads :.'sliding side doors and upper and lower covers. The fan projects through the front bulkhead and is belt-driven ; the air which is drawn through the rearward-facing radiator is allowed to escape at the sides and top of the fan compartment. Inlet air first passes through a gauze at the top of the intake pipe and then through a Garrett oil-wetted filter to the cylinders.
Normally the work of the tractor will be to haul trailers carrying oil-drilling equipment. At times it will be employed as a stationary power unit for driving electric-welding generators ; for this purpose a pulley driven by a power take-off projects from the back end of the frame. It transmits full engine power.
Other special fittings for the work, which were not installed at the time the machine was photographed, are an apron plate for the driver's cab, rollup side curtains and accommodation for carrying men above the track guards beside the engine housing.
A drawbar-pull test was carried out, hauling a 12-ton trailer with its brakes applied. The two-speed gear was in " low " throughout ; in first gear 9,000 lb. was exceeded, over 6,000 lb. in second speed and over 4,000 lb. in top gear. At the end of the trial, which took place on a hot day, the water temperature was 138 degrees F.
Since this type of tractor was introduced, the operation of the two levers for the track clutches and brakes (i.e., the steering controls) has been improved and made lighter. Control in general is easy and the engine pulls sturdily in all gears, without signs of labouring after a change ; in the low range the road speeds are 2 m.p.h., 3 m.p.h. and 4 m.p.h., whilst the high series gives three times those rates of travel. Fuel consumption is in the order of 2 gallons per hour and the tank holds 25 gallons.