[Illustration: Metal Parts Screwed on Leather Hinge]
hoops, zinc or thin brass cut in neat designs will make a leather hinge appear as well as a metal hinge. --Contributed by Tom Hutchinson, Encanto, Cal.
A hot-water bottle held against a porous plaster will assist in quickly removing it from the skin.
For the frame use 3/8-in. round iron, bending it as shown in the diagram and filing a knob on each end, at opposite sides to each other, on which to hook the blade. For the blade an old talking-machine
spring or a clock spring will do nicely. Heat the spring enough to take some of the temper out of it, in order to drill the holes in the ends, as shown, and file in the teeth. Make the blade 12 in. long, with 10 teeth to the inch. A and B show how the blade fits on the frame. -Contributed by Willard J. Hays, Summitville, Ohio.
A cannon like the one in the cut may be made from a piece of 1-in. hydraulic pipe, A, with a steel sleeve, B, and a long thread plug, C. Be sure to get hydraulic pipe, or double extra heavy, as it is sometimes called, as common gas pipe is entirely too light for this purpose. Don't have the pipe too long or the cannon will not make as much
noise. Seven or eight inches is about the right length for a 1-in. bore. Screw the plug and pipe up tightly and then drill a 1/16-in. fuse hole at D.
If desired the cannon may be mounted on a block of wood, F, by means of a U-bolt or large staple, E. --Contributed by Carson Birkhead, Moorhead, Miss.
An easy way of making a controlling and reversing device for small motors is as follows:
Cut a piece of wood (A) about 6 in. by 4-1/2 in., and 1/4 in. thick, and another piece (B) 6 in. by 1 in., and 1/4 in. thick. Drive a nail through this near the center for a pivot (C). To the under side of one end nail a copper brush (D) to extend out about an inch. On the upper side, at the same end, nail another brush (E) so that it projects at both sides and is bent down to the level of the end brush. Then on the board put
a semi-circle of brass-headed tacks as shown at F, leaving a small space at the middle and placing five tacks on either side, so that the end brush will come in contact with each one. Connect these tacks on the under side of the board with coils of German-silver wire, using about 8 in. of wire to each coil. Fix these by soldering or bending over the ends of the tacks. Then nail two strips of copper (G) in such position that the side brush will remain on the one as long as the end brush remains on the tacks on that side.