Seven Tons on a Four-wheeled Steamer
Page 42
If you've noticed an error in this article please click here to report it so we can fix it.
WITHIN the legal gross, weight of 13 tons allowed for fourwheeled steamers, the Sentinel Lightweight, of which we published a road-test report on June 14, 1932, proved able to carry a pay-load of 5 tons 15 cwt.. The Sentinel Waggon Works, Ltd., Shrewsbury, has now produced an entirely new machine, which, with flat platform body of Sentinel manufacture, is claimed to carry a legal load of 7 tons ' or, with trailer, 14 tons. A six-wheeled model is made for loads of 10-11 tons.
The engine of this interesting new _ machine is a four-cylindered singleacting glandless unit, of 51-in. bore and 6-in, stroke, disposed axially in the frame, and having an accurately balanced crankshaft. There is pressure lubrication to the main and crankpin journals and, through the hollow connecting rods, to the gudgeon pins. The use of trunk-type pistons permits crossheads, piston rods, packing and guidesto be dispensed with.
The oil sump has sight-level glasses fitted, likewise the timing-gear chamber and gearbox. The main oil supply passes through a readily detachable filter and is delivered to the main bearings, timing gears, camshafts and to the gearbox shafts and gears, the supply being forced, according to automobile practice, through holes in the crankshaft to the big-end bearings, whilst the cylinder walls are lubricated by splash.
The steam and exhaust valves, of the poppet type, are located in the cylinder head and are operated by separate camshafts, arranged to provide three forward cut-off positions and one reverse position. The valves are accessible.
The slow-running double-acting feed pump gives a steady flow of water and eliminates the hammering of check valves, which occurs with the usual type of single-ram pump.
In the Automatic model, which incorporates a mechanical stoker and automatic feed-water regulator, the feed pump is controlled by a thermo-feed apparatus. The pump and its driving gear constitute a unit, which may be removed in a few minutes.
Although isolated from the crankcase, the two-speed gearbox forms a unit with the engine, and provides direct top gear and a ratio of 2.72 to 1.
As to the main structural features, 3324
the frame comprises nickel-steel side members with tubular and channel-section brach-1gs and ample gusseting. The front axle is an H-section drop forging, and front-wheel brakes can be provided if required. The detachable wheels normally carry extra-heavy 40in. by 8-in. tyres (twin rear).
The transmission is through a cardan shaft of large diameter to a threequarter floating rear axle, and this incorporates a double-reduction gear comprising a spiral-bevel drive to the lay
tubes and double superheater coils; the working pressure is 255 lb. per sq. in.
The throttle of the new machine is foot operated and has a shut-down valve on the steam chest. The brake lever, gear change and camshaft-control levers, also the pump by-pass lever, are conveniently placed, and the driver sits forward of the boiler and has an excellent view of the road. The capacity of the feed-water tanks fitted at the sides of the boiler behind the seats totals 170 gallons, sufficient for 50 miles, whilst the bunkers, filled through hatches in the cab roof, and having convenient firing apertures, are placed above the feed tanks and have a capacity of 5 cwt., sufficient for 120-150 miles of running. Electric lighting equipment is included.