AN AMERICAN TWO-TON STEAM LORRY.
Page 7
If you've noticed an error in this article please click here to report it so we can fix it.
By. an American Correspondent.
DUE, doubtless, to the enhanced price of petrol ; possibly, also, to the recognition of the reliability of steam engines for road work, several steam lorries are being offered to the American user. One of these in particular, the Doble, has had a very fair run of success. The Doble steam lorry is at present offered in one model—a 2-tormer --by the Dohle Laboratories, San Francisco, California. It is the intention of the company, however, in the near future to bringout firstly, a 15 cwt. general utility vehicle, and then *ton and 5-ton neavy steam lorries.
Paraffin fuel is used for evaporating the water in the boiler, and the latter is carried in a hood of the conventional shape and in the usual position. The engine is a two-cylinder horizontal model ; its crank end is bolted directly to the stationary I-beam loadcarrying element of the rear axle. The engine suspension is arranged so that rather more than twothirds of the engine weight is spring-supported. It will be seen from the accompanying illustration that the valve gear is of the Joy type. Automatic control is provided for the steam pressure, and for the temperature and quantity of water supplied to the boiler. In the latter the paraffin is broken up into a fine fog by means of an atomizer, which consists of a rapidly-revolving steel howl mounted on an extension of the spindle of an electric motor. Immediately below this revolving bowl, and mounted on the same shaft, is an air pressure fan ofthe requisite size to deliver the definite quantity of air that is required for complete combustion: the paraffin pump is delivered from the shaft of the same electric motor. Rings for producing the electric spark that ignites the fuel are also mounted on the motor shaft, Paraffin from the fuel pump is delivered to the centre of the revolving howl and, due to the rotation of the latter, is discharged over the edge of the howl in the form of fine mist.
To start the vehicle, all that is necessary is to operate the switch that starts the motor. This combustion system is bolted to the side of the boiler,
and the products' of combustion are discharged directly into the top of the bOiler, being forced in a downward direction around the tubes, finally issuing from the bottom of the boiler at a very low temperature. The boiler is of the inverted flash type, and is constructed of seamless drawn-steel tubing of small diameter. While the hot gases enter the boiler at the top) water is brought in at. the bottom. The boiler is controlled automatically by a positive temperature device, consisting of a seamless steel tube, through which the steam must flow on leaving the boiler for the engine. A tube made of special metal .is inserted in the main outlet tube. The former tube is closed at"the inner end and, is connected with a rod made of special steel As the temperature in the combustion chamber and the boiler rises, the inner -tube increases in length to a greater degree than the exterior steel outlet tube. This causes the inñer steel rod tO. Move and Open at,'the desired point, the electric control of the motor thus stopping it. " Attached to this same automatic temperature Control is -a steam pressure' Control so constructed that, when.the steam reaches the determined pressure, the motor. Circuit is opened and the fire extinguished. When the steam pressure is lowered again, the electric circuit is closea automatically and the motor started. The steam passes directly from the boiler to the engine and the now is throttle controlled. The exhaust steam is carried back to a condenser, which occupies the place of the ordinary radiator.• The condensed .steam is passed through a steam turbine blower on its way to the eondenser, to furnish additional volume of cooling air. A storage battery, and an electric generator to keep it charged, complete the equipment. The battery provides electric energy for starting the car and for furnishing lights when the vehicle is standing. The frame of the lorry is made of channel sections 6 ins, deep, and the wheels are of cast steel with hollow spokes.
The evolution of the present Doble 2-ton lorry dates back to 1906, when the first experiments Were begun, The following salient features of the specification are of interest :—Capacity 4,000 lb. ,• price £710; wheelbase 12 ft. ; tyres, front 36 ins. by 4 ins., rear 36 ins. by 7 ins. ; bore 5 iris; stroke 4 ; final drive, internal gears.