Pioneering the " FlatTwelve" fir passenger service
Page 19
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American White Company Produces Design of Horizontally opposed Petrol Engine Which is Built in Three Sizes to Power Fast Passenger Chassis Ranging from 31 to
40-seaters
I N view of the interest that is now being taken in this country in engines of the " pancake" type, it is of note that marked progress along these lines is being made on the other side of the Atlantic.
A recent introduction is a range of three petrol engines, having 12 horizontally opposed cylinders, which has been produced by the White Motor Co., Cleveland, Ohio. These form the power units of three new buses with seating capacities of 31, 36 and 40 respectively.
Big claims are made for these vehicles, a speed of 50m.p.h. being attainable, according to the maker's statement, in 28 seconds, whilst we are informed that excellent characteristics have been revealed in respect of economy, and vibrationless and silent running.
Accommodated under the floor, the engine has a three-speed constant-mesh gearbox bolted to it at the rear, and at the front end are grouped the dynamo, fuel-lift pump, and threecylindered air compressor, a triple belt transmitting the drive. The unit is supported on rubber at three points. There is a starter above the engine, arranged slightly to the right of the centre line, and the carburetter, which has a double throat, but a single floatchamber, is mounted above the middle of the crankcase.
Hydraulic Throttle Control.
This auxiliary is controlled by two throttle valves on a common shaft, operation being by the Bendix hydraulic system. The distributor is housed between the carburetter and the front end of the starter. Two oil filters are accessibly accommodated under the air compressor.
Detachable cylinder heads accommodate the sparking plugs, and give access to the valves, disposed side by side on the undersides of the two banks of cylinders. A neat cover protects the projecting parts of the plugs, and the valves are of austenitic steel and have inserted seatings, provision for jet cooling of the ports being made. A particularly interesting point is the employment of " zero-lash " hydraulic cam followers—tappets which automatically maintain by hydraulic means the minimum permissible clearance at the valve stems.
Alloy-iron dry cylinder liners are used, and aluminium-alloy pistons. Lubrication of the gudgeon pins is assured by rifle-drilled connecting rods, the big ends of which have steel-backed white-metal bearings. Of 2 ins, diameter, the seven main bearings have a total area of 37.2 sq. ins.; and the integrally forged counter-weighted crankshaft has Tocco electrically hardened journals. A vibration damper is provided.
For the high speeds and rapid acceleration demanded in America, engines of considerably greater power than in this country are needed in vehicles of similar weights. The power unit specified 'for the White 31-seater develops 170 b.h.p. and has a displacement of 530 cubic ins. (8.68 litres). For the 36-passenger vehicle, a 189 b.h.p. engine is employed, which has a piston-swept volume of 601 cubic ins. (9.84 litres). In the case of the 40-seater, the output is 211 b.h.p. and the capacity 681 cubic ins. (11.13 litres). At 1,200 r.p.m. these three engines exert, respectively, torques of 385 lb.-ft., 435 lb.-ft. and 500 lb.-ft. They are not governed and are normally run up to 3,000 r.p.in.
Carrying the maximum number ot passengers (SO per cent, overload), the three buses weigh, respectively, 188 cwt., 206 cwt. and 223 cwt., therefore their respective power-to-weight ratios, in terms of b.h.p. per cwt., are 0.905, 0.918 and 0.948. These are markedly higher than would be used in this country, whilst with the rated number of passengers they obviously become higher still—somewhere in the region of 1.1.
In this connection it is of interest that the three buses, unladen, weigh, respectively, about 124 cwt., 133 cwt. and 142 cwt.
They have all-metal bodies, in which aluminium alloys are widely used and a design followed by which the body gives strength to the whole vehicle, instead of being constructed as a separate entity relying entirely upon the chassis for its support. It has a forward entrance and an exit just in front of the rear wheels, both doors being of the double jack-knife type, pneumatically operated. There are, of course, no obstructions above floor level.
Constant Change of Air.
In carrying out the design of the bodywork particular attention has been paid to the question of ventilation, the roof being formed as a duct, and the air is changed at th'e rate of 10 cubic ft. per minute per seated passenger. For use during cold weather there are hot water heaters.
Finally, an interesting point is that the engine-cooling radiator is placed in the middle of the rear panel, and air is discharged, by fan, into the vacuum pocket, where it helps to break up trailing exhaust fumes.