Leyland Oil Engine in Bedford 7-tonner
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HYLAND Comet 350 oil engines are I-Abeing installed in Bedford S-type coach, long-wheelbase lorry and tractor chassis by the Arlington Motor Co.. Ltd., Ponders End, Enfield, Middx. The conversion costs about MO and this sum is, according to the Arlington company, recovered in 40,000-50,000 miles. The Bedford petrol engine remains the operator's property.
Trials with a 7-ton load over a local route of 411 miles, embracing fairly heavy traffic, produced returns of 17 m.p.g. of oil fuel and 8-i m.p.g. of petrol. This indicates a saving in fuel cost of over 3d. per mile, and on the basis of 1,000 miles operation per week, the oil-engined vehicle costs £.12 10s. less louse.
Because the maximum torque of the Bedford and Leyland engines is almost the same, the transmission is basically unchanged, the major modifications being to provide cast brackets at the front cross-member to connect with the standard Comet mountings, and to alter the Leyland engine rear member to fit in the Bedford chassis. The conventional Leyland link mounting and snubber bracket are used at the rear.
The clutch supplied with the oil engine is employed, with a new centre plate having a splined hub with an extended spigot to accommodate the existing Bedford four-speed synchromesh gearbox primary shaft. A steel plate is attached behind the clutch housing to locate the fixing points of the gearbox.
As the replacement unit is slightly longer than the Bedford engine and gearbox, the second cross-member is modified to clear the gearbox selector turret and, at the same time, to provide a platform for carrying one of the cab mountings. The propeller shaft is shortened by 31 ins. A rear-axle ratio of 5.833 to 1 is standard in the converted coach and long-wheelbase chassis, and 6.8 to 1 in the tractor.
Because of the flexible engine mounting, the Leyland exhaust pipe is
connected to the Bedford silencer by a two-piece system joined by a metallic hose, the fuel-supply and gallery return pipes between the frame and engine being connected by neoprene rubber hose. An additional filter is provided in the fuel system. The extra weight imposed on the front axle by the oil engine is within the limits specified by the chassis manufacturer, and is taken care of by three additional leaves in each of the front springs.
Although the Bedford radiator is used, the additional height and width of the Comet engine and its air filter have required alteration to the cover in the cab. The top plinth is extended at the front and a removable panel is provided at the near side for access to the fuel-injection pump and exhauster.
The Leyland elliptical vacuum reservoir tank is fitted inside the chassis frame and a duplicate set of 12-volt batteries is placed in the cab or on the frame, according to the type of chassis, for 24-volt starting equipment.
During prototype tests of the converted long-wheelbase model, fitted with a standard drop-sided body, the tare weight, complete with spare wheel, tools and full fuel tank, was 3 tons 5i cwt. The vehicle, having the 5.833to-1 ratio axle • and carrying a 7-ton payload, completed the, course at an average speed of 28 m.p.h., with a fuel return, as already stated, of 17 m.p.g. Trials made with 8.25 and 9.00-20-in. tyres indicated that fuel economy was not materially affected by tyre size.