New Atkinson Passenger Chassis TWO new lightweight underfloor' engined passenger
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chassis are being built by Atkinson Lorries, Ltd., Preston, one of which will be used as a demonstration bus at the Commercial Motor Show. The power units are Gardner 5 HLW and 4 HLW horizontal engines and a new five-speed gearbox, with constant-mesh dog-engaged gears for all ratios, will be fitted.
The frame is similar in over-all dimensions to the larger-engined models, but its thickness is reduced by 1/16 in. to .5/16 in., and the flange width is 21 ins. A wide frame is employed, thus obviating the use of outriggers. The overall width of the frame at the front is 3 ft. 8 ins., broadening to 4 ft. 1 in. from behind the front axle to the tail. At the rear the frame is tapered from 8 ins, maximum depth to 5t ins., so as to-lower the entrance to the body.
Further weight is saved in the section of material used to join the crossmembers to the main longitudinals. The fish plates and spring brackets are fabricated from 3/16-in, steel plate, and the pressed-steel inverted U-section A30 engine rear cross-member is of lighter pattern than that employed in the sixcylindered cha,ssis. A Clayton Dewandre triple-servo braking system is employed, the master cylinder being located inside the frame, adjacent to the propellor shaft, on a fabricated bracket which also carries the fulcrum pin for the hand and foot-brake levers. The vacuum reservoir is mounted inside the frame on the front overhang, where it is in a position to shield the radiator from mud.
The cross-members are arranged in the frame to coincide with the spring anchorage points, thus reducing the number of holes drilled in the vertical section. As in other Atkinson chassis, the front and rear members are of pressed-steel channel section and the remainder, apart from the engine rearmounting member, are tubular.
It has been calculated that with standard 9.00-20-in. tyres, the chassis Weight will be under 4 tons with the fivecylindered engine fitted. The chassis is designed for either a fouror fisiecylindered engine.