The next step is to connect the top and bed-plates by four pillars. The length of these will depend on the length of the piston-rod. They must be made of four pieces of brass wire a quarter of an inch thick. Take one of the cylinders and a sheet of paper; on this paper draw a line about six inches long, and at one end mark the point A (Fig. 10). Push the piston-rod in as far as it will go, and push the pivot of the cylinder through the point A, and mark on the line the point B, exactly under the hole in the crosshead of the piston-rod. Now draw out the piston-rod as far as it will go, and mark the point C exactly under the hole as before. Bisect the portion of the line between B C in the point D, and measure the distance between A and D. Reduce this length by the distance the centre hole in the steam-blocks is from the lower edge, and add to it a quarter of an inch for the height of the centre of the bearing-block from the upper surface of the bed-plates, one-eighth of an inch for the thickness of the bed-plate, and a quarter of an inch for riveting.
This will give you the length of the pillars including the pins. File a pin and shoulder at each end, as in Fig. 11, making the pins one-eighth of an inch in diameter and a quarter of an inch long. Rivet a pillar firmly in each corner hole of the bed-plate, and put the top plate on the top ends of the pillars, and rivet them firmly in. Be careful that the pillars are upright. Rehang the cylinders and unscrew the caps of the crossheads. Fit the cranks into the holes in them and screw on the caps.
If the cylinders are made without screw-crossheads the pin of the cranks must be placed through the hole in the heads before riveting the cranks together. Unscrew the caps of the bearing-blocks, and put the crank-shaft into the bearing-holes, and screw on the caps again. Oil all bearings and parts that work together. Now you must get a heavy brass fly-wheel three inches in diameter, which can be purchased with the other things, and costs about two shillings. This wheel has a screw-bolt through one side of the centre block to fix it to the shaft by. Fix this wheel on the long end of the shaft by tightening the screw. It would be better to make a small hole in the shaft for the point of the screw to enter. The wheel must have two iron pins, about one inch long, in the face of it.