Make the tail piece first. In the cross pieces of the tail piece are two screws 7/8" from the ends; be careful to bore the holes large enough so the screws will not split them. The edges of the lower cross piece must be sandpapered enough not to cut the elastic bands.
In order that the belt shall run on the center of the wheels in the head piece, it is important to have the three axles parallel. To make them so, the two uprights must be clamped together while boring the 3/8" holes for the axles. Lest the spur of the bit split the uprights, drill small holes at each center first. Do not nail the longer upright to the base until the belt runs well in both directions. On a lathe, the wheels and axles could easily be made of one piece; lacking a lathe, a big spool or curtain pole must be used. Plug the hole of the spool with a dowel, then very accurately find its center and bore a 3/8" hole thru it. Saw it into three 5/8" pieces for the wheels. Glue these to the axles so that 1" extends thru the taller upright. A belt runs better on a wheel that is "crowned," that is, slightly larger in the middle; so the edges of these wheels must be pared 1/32", making a gentle curve. Put the washers each side of the wheels, then put the wheels in place in the taller upright, and nail this to the triangular block. Pull a 5/8" leather belt tightly around the three wheels and sew the ends so that they butt together. Clamp the shorter upright in position and turn the upper axle to see if the belt runs well in both directions. It will run true when all three axles are parallel, so keep knocking the shorter upright from side to side or up and down until the belt does run true; then bore holes for three screws to hold it to the triangular block. Make the crank and lock it to the upper axle with a 1/2" screw.
To twist a string, set the two parts of the machine somewhat farther apart than the finished length desired, put on as many
threads, from hooks on the tail piece to corresponding hooks on the head piece, as will make the finished string the desired size. Observe how these separate threads were twisted, and start the machine in the opposite way. Twist until the three strands kink readily when the head piece is brought nearer the tail piece. The tighter these are twisted, the harder the string will be. (Soap rubbed on the inside of the belt may make the belt carry more power). When these three strands are twisted enough, remove the two lower ones from their hooks on the head piece to the upper hook. Twist in the opposite direction until the string kinks again, and it is made. If the three strands are waxed, a stronger string will be made.
[WINDMILL FORCE-PUMP—][Plate 35].
If this pump is properly connected with an air chamber, as explained later, it will send a small stream of water some ten feet. In a gale, the windmill is strong enough, in fact, to force the valves from the glass tubes. Like any model of considerable mechanism, this will require patience to get it in working order. The post is made short for stability. If it can be held in place firmly, a trestlework tower like a real windmill might be built of stock 1/2" × 1/2" for the corner posts and 1/2" × 1/8" for the braces.
The post is slanting on two sides to fit the journals at the top. It is fastened to the base with two 2" screws. Make the wheel center 2-1/8" square, and thru its center bore a 1/4" hole. If it does not revolve true, make another block and try again. Make the block octagonal by cutting off each corner 5/8". On each of the eight faces saw notches 1/8" wide and 5/16" deep into which the vanes will fit. (See [page 64] on cutting notches.) Make and glue the vanes in place and lay the wheel flat to dry.
Procure three pieces of water-gage glass 2" long, 7/16" to 1/2" inside diameter. Glass tubes can be broken apart by filing a slight notch, grasping the tube firmly each side of the notch, and pulling and bending the tube away from the notch. If the file starts a little break, this will be comparatively easy, if it does not, file some more. Into two tubes little valves must be cemented. These can be made of a firm piece of leather. Sole leather that is not too hard is best. With knife or chisel, pare two pieces on the cutting board to fit in the tubes. The cement will make them water tight later. Push the sharp point of a penknife into the smooth side of the leather disk and make a circular cut, as one would remove a speck from an apple, but do not cut the flap completely out, because it must be left hinged to the disk. Turn this flap up straight out of the way so as to be able to work a 1/4" hole thru the disk. This can be punched, drilled, or cut out with a 1/8" chisel, and finished with a penknife. Of course, the edges of the flap should cover this hole completely. The valve in the lowest tube should be cemented about 1/2" from the lower end with the flap up, that in the horizontal tube about 3/4" from the outer end with the flap out.