Minimum Gauge Railways

by bart. Sir Arthur Percival Heywood

The safety-valve spring is entirely within the boiler, so that it cannot be tampered with or injured by accident.

The connecting-rod brasses are peculiar. In order to avoid the twist to the slide bar when the driving axle, owing to inequalities in the road, fails to preserve its horizontal parallelism with the frame, the brasses are shaped circular, so as to turn slightly in their straps, the latter being bored out in the direction of their length instead of slotted. This plan not only relieves both crank-pin and slide-bar of torsion, but also forms a much more rigid union between the strap and the rod end.

The steam jet is worked by the regulator handle, the valve being so arranged that when the handle is moved beyond the point at which steam is shut off, the jet is opened. A spring stop prevents the jet being opened inadvertently. Thus when steam is put on, the jet is by the same action closed, steam is saved, and two motions are performed in one.

An important point in this, as in all the locomotives I have built, is that the over-hang at the two ends is equal, and the weight also on both leading and trailing axles practically the same, when the driver is on the foot plate. A further arrangement of value is that in all my engines the cranks are counter-balanced. It is impossible to effect the counter-balancing on the wheels, nor, even if feasible, will the result be so good, as counter-balance weights on the wheel are not at the same distance from the axle centre as the disturbing weights, and therefore not equable in their effect at different speeds.

This engine was built for tractive power, not speed, and eighteen miles an hour is the highest rate registered over the short straight course available. The previous engine, with 15½ in. wheels, reached a speed equal to 23 miles an hour, the time being in both cases taken over a measured distance with a stop watch. About 11 miles an hour is the usual average speed with passenger cars, which, owing to the severe curves, it is not deemed wise to exceed.

The net cost of the engine under consideration was £309, exclusive of drawings and patterns. At the time it was built a joiner and occasionally a labourer were my only assistants; the work consequently proceeded but slowly, occupying altogether two years and a half. Reducing the time to hours, the whole of my own labour was almost precisely equal to that worked in one year by an artisan, and that of my assistants together to about half the amount. This includes the time occupied in moulding, for all the castings were made on the premises, with the exception of the steel wheels.

The boiler, frame-plates, and some of the brass fittings, were purchased, but the whole of the machine work and fitting was executed on the spot. The cost of all material, the hours of labour and engine power, interest on tools, &c., were all carefully booked, and it will probably not be far from a fair trade price for the engine if 10 per cent, for drawings and patterns, and 20 per cent, for profit, are added to the cost given above, thus bringing the amount to about £400.

The working of the radiating gear of engine No. 2 proving so satisfactory, I elaborated the principle so as to apply it to an eight-wheeled locomotive. (No. 3 in the table.) In this case both of the middle pairs of wheels have the traversing motion already described, but, instead of the leading and trailing wheels being radiated from one central pair, the second pair of wheels radiates the leading pair, and the third pair of wheels the trailing pair, thus forming a mechanism practically equal to a double bogie. By this arrangement an eight-coupled engine is obtained capable of passing round curves as severe as may be necessary. In the present instance, the travel is constructed for a minimum radius of 25 ft. The details of the engine are similar to those of No. 2, but numerous improvements have been effected, into all of which it would be tedious to enter. It may, however, be mentioned that the ends of all the crank pins are boxed in by the connecting and coupling rod brasses, to exclude dirt. A steam water-lifter has also been added, by which the tanks can be filled without delay during frost.

The blast-nozzle is made adjustable by raising or lowering an internal cone. Owing to the steep gradient before alluded to, it was impossible to get a fixed size of nozzle that would keep up steam with a light load on the level, without being so contracted as to lift the fire off the bars on the incline.

The boiler fittings have been made as symmetrical as possible, and circular nuts have been substituted for hexagon, as more easy to clean. The water-gauge glasses are put in through the top cock and fastened by a single cap nut, thus doing away with the usual external glands. The steam brake has a 5 in. cylinder, and the rigging is arranged to swing with the traversing wheels.