The Latest Mann Wagon.
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Successful Application of Hopper-fed Stoking to boiler of Two-Ton Steamer.
This vehicle is constructed to carry loads of two tons at a speed of eight miles an hour, upon metal tires, and up to 12 miles an hour on rubber tires. At these speeds, stoking with a shovel is apt to occupy too much of the driver's attention. Coke or coal is therefore carried in a hopper, which is fixed directly over the fire box. The bottom of the hopper is sloped to an outlet which can be opened or shut by a slide that is operated by a hand lever. A short tube, the capacity of which is equal to a charge of fuel, is fixed under the outlet in the bottom of the hopper, and is so constructed that the side nearest the driver forms a door which can be opened when desired. This hinged portion is formed like a grid or grating, and the lower part of the tube is provided with a second slide, so that, after each charge is delivered, the driver can see through the firing hole when the bottom slide is opened. On opening the top slide, the fuel from the hopper falls into and fills the fire tube, when the top slide is closed. Whenever the bottom one is opened the fuel falls on the fire and the bottom slide is then closed for the re-filling of the tube. In this manner, a definite quantity of fuel can be fed at a time, and as frequently as required. When the wagon is standing, the driver can use fuel out of the bunker in front of him, by opening the bottom slide and hinged front of firing tube, thus reserving the fuel in the hopper for use when travelling.
A large dome is riveted on the top of the barrel, and this is fitted with a dished cover, secured with studs, in order to permit ready access to the inside of the boiler for examination and scaling. The dome allows of an increased height of the working water level, and this ensures that both the fire box and the front of the, top row of tubes are covered with water when going up or down hill. The engine is of the compound-horizontal type, and
works in an oilbath. The diameter of the high-pressure cylinder is 3,1, inches ; that of the low-pressure cylinder is 61 inches; and the piston stroke is 6 inches. The main-axle springs are 4 feet long, but in order still further to reduce the vibration, and to make these wagons suitable for the carrying of delicate articles upon steel tires, at eight miles per hour, a second set of springs have been added between the main-channel girders and the platform. The cost of upkeep of india-rubber tires upon macadamised roads is such a serious expense upon steam lorries, that the advantage of using double springs as an alternative is at once apparent. A second illustration, showing the general appearance, will be found on page 522.