This website has been archived from TrainWeb.org/i3 to TrainWeb.US/i3.

Wilkinson by D. Kinnear Clark

contents

The following is transcribed from a reprint of Tramways - Their Construction and Working, by D. Kinnear Clark, with the kind permission of the publisher.

Wilkinson.

The worm-geared condensing tramway locomotive of Mr. W. Wilkinson combines a few original elements. Acting on the results of Mr. Dewrance's experiments on the evaporative activity of different parts of a locomotive boiler, Mr. Wilkinson designed a short locomotive boiler, having flue tubes only 12 inches in length. His object was to maintain the water level in the boiler practically constant whether on level ground or on steep incline such as 1 in 11. The tubes are not straight, but of an ogee form, in order to yield to expansion without the liability of breakage. The steam is exhausted into a condenser fitted with tubes also of ogee form presenting between 200 and 300 square feet of condensing surface. The steam surrounds the tubes, and the air for cooling them is drawn through them into the ash-pan to support combustion. The steam that remains uncondensed passes into a superheater in the smoke-box -- a rectangular box fixed against the tube plate, traversed by tubes coincident with those of the boiler, through which the burnt gases flow into the smoke box.

While running on a level line, with a heavy load, in or nearly in mid-gear, there is scarcely sufficient steam left uncondensed to cause the necessary draught, and in such a case the draught is sharpened by reducing the blast orifice, in applying a thimble to the top of the blast pipe, which is done by hand with a lever.

In the fire-box a number of Field tubes are fixed to the root between the roof-stays.

The power of the engine is transmitted through worm-gear to the driving axle. The worm is double-threaded, and one turn of the axle is made for 7½ turns of the worm. The diameters of the worm and the wheel are equal, or nearly so-- about 12 inches in diameter ; and the obliquity of the worm-thread is so considerable that, on a falling gradient of 1 in 70, the worm is propelled by the force of gravity. The worm is of Siemens steel, and the toothed wheel runs in an oil bath, providing constant lubrication. the carrying wheels are 3 feet 2 inches in diameter. There are two cylinders working to a logitudinal crank axle. It is stated that the engine can draw a loaded car, weighing 3 tons, full of passengers, on a level or nearly level road, with the valves in mid gear ; the steam being cur off at 9 per cent. of the stroke. At the regulation speed of 8 miles per hour, the speed of the pistons is 436 feet per minute. The engine has been worked at a speed of 16 miles per hour. The machinery is compactly placed, and the cylinders, guide bars, valve gear, foundation plate, worm, and plummer-blocks can be removed for repair by undoing six bolts, and a duplicate substituted.