Fig. 8.
The cranks should be at right angles to each other, and the throw of the crank is to be half the distance of the cylinder stroke. For instance, say the cylinders are an inch and a half in stroke, the distance between A B ([Fig. 8]) will be three-quarters of an inch; you must then ease the size of crank at A, to prevent the piston knocking the cylinder ends.
The cylinders require such extreme care in turning that it is by far the best plan to buy them ready to put on your framework; and if you get a pair of oscillating ones three-quarters of an inch bore and about an inch and a half stroke, you will get sufficient power to drive your locomotive several miles an hour.
Fig. 9.
[Fig. 9] shows you an underneath view of the framework and the position to place the cylinders in, which should be supported by a couple of lugs (A A) screwed to the bed-plate B which must have a piece cut out on either side to allow the driving-wheels (C) to work in, as at D, because, being larger than the others, they project beyond the top of the bed-plate, as shown in [Fig. 2]. You can now screw on by means of the hook F the buffer-beam, previously cut from a piece of mahogany, five inches long, half an inch thick, and one inch deep, nicely squared and sand-papered.
Drill a hole at G and pass the shank of hook through the beam and piece of brass in front of frame, and screw up tight with nut H.
The buffers can be properly turned up and fitted with springs, but that I will explain when making our more perfect model, and content ourselves now with a couple of brass flat-headed screws, such as are used in connections of electric batteries, and which form capital imitation buffers, one having to simply screw them into the beam about one inch from either end, leaving them projecting about half an inch.
The framework is now sufficiently complete to be lacquered. First polish every part intended to be bright, carefully removing all traces of file-marks and any grease that may be on the work by a little acid; and after drying it place it on a sheet of iron held over the gas—or fire, if clear—until it is moderately warm. You can then apply the lacquer with a small brush, taking care not to go over any part more than once. The lacquer can be had at most model shops, and is cheaper to buy ready-made than to prepare yourself.