GM gas turbine and new Allison gearbox at Show
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• An infinitely variable power-transfer mechanism that is claimed to provide outstanding performance advantages is a feature of the Detroit Diesel GT 309 280 bhp regenerative gas turbine that will be shown for the first time outside America at Earls Court by the GM Power and Industrial Division of General Motors Ltd. London Road, Wellingborough, Northants.
Also to be displayed on the same stand. an Allison fully automatic gearbox, the AT450 is the first of an entirely new range of transmissions designed to fill the gap between the larger type of car transmission and established commercial vehicle fully automatic units. Detroit diesels on show will comprise the V-71 range of engines with outputs between 195 bhp and 434 bhp.
The OT 309 is scheduled for initial production "in the near future," and will be one of a series of four models with outputs ranging up to 2000 hp that will augment the power coverage afforded by the division's diesel engines.
Connecting the gasifier shaft to the power turbine shaft by means of an oil-cooled clutch, the power transfer device enables the engine to run with the two turbines locked up, or to run with the turbines operating separately with 100 per cent slip across the clutch. The device gives power-turbine overspeed protection. greatly improved overrun braking and reduced fuel consumption and it combines the operational advantages of fixed-shaft and dual-shaft turbines. The production engine will weigh approximately 14251b. By inCreasing the air flow, the output could be increased to 400 hp. which would add about 751b to the weight.
It is claimed that the power-transfer unit provides a saving in fuel consumption of 28 per cent at 50 per cent load, the consumption at 100 per cent load being comparable with that of a unit without power transfer. The rated output is based on an output shaft speed of 3000 rpm. the speed of the gasifier turbine being 36.000 rpm on full load. While the torque of the engine is 575 ft lb at 3000 rpm it increases to 1750 ft lb with the shaft stalled.
The rated torque and stalled-output-shaft torque of the 400 hp engine are approximately 790 and 1580 ft lb respectively. Pressure ratios are 3.8 to 1 and 5.1 to 1 respectively. A width of 26in. and a height of 40in. are common to both engines. the lengths being 45in. and 54in. respectively. The block is made of cast iron.
The Allison AT 540 Show model is a torque convertor /planetary gear four-speed transmission designed for petrol engines of up to 200 bhp and a maximum torque of 325 ft lb. A basically similar model modified to cater for diesel engines of the same output and torque retinas will be available by the spring of next year. The ratios in both cases are 3.45 to 1, 2.25 to 1. 1.41 and 1 to 1, reverse being 5.02 to I.
It is claimed that the transmission gives a "completely shock-proof" drive and the gearbox is therefore particularly suitable for multiple-stop-start work. Features include a three-element torque convertor and oil-cooled disc type range-change clutches that are hydraulically operated and are self compensating for normal wear. Options include a convertor-driven power take-off which provides infinitely variable ratios matched to the load. Ratio changes are made automatically according to variations in vehicle speed and engine load.
The gearbox has a length of 27.22in., a width of 20.72in. and a height of 18.90in. Its dry weight is approximately 2751b.