Drill a hole in beam to allow the head of pin to work in freely, and another hole in base-plate of buffer the size of pin, whose head prevents the spring forcing C entirely away from A.
The spring should be made of thick steel wire; the buffers can then be screwed on as just mentioned. The wheel-guard, or line-clearer P ([Fig. 20]), can next be cut out to shape and bolted on to frame, and should just clear the line by a quarter of an inch.
We will now proceed with the axle-bearings and springs U ([Fig. 20]). The wheels can be finished up in the same manner as previously described, so I need not say anything further about them.
Fig. 25.
Make a wooden model like [Fig. 25] and get six castings in brass made from it. They then must be filed up square and smooth and fitted into the slots cut at A B C ([Fig. 22]), and either screwed or riveted on by the side holes.
Before finally fixing them prepare six brass bearings (B, [Fig. 25]). They must fit exactly, and slide easily in the inner surface of A, and a hole is to be drilled centrally through each five-eighths of an inch in diameter. These take the axles, which in this model are all straight, and three-quarters of an inch in diameter, shouldered off to five-eighths for the bearings.
Fig. 26.
The springs next require attention. Four pieces of either sheet iron or brass are wanted in each support an inch and a half long by a quarter wide. A hole is to be drilled at either end, as shown at C in [Fig. 26]. A should be three-eighths of an inch wide, drilled through and a pin put in, and all riveted together loosely.