Fig. 76 shows
A Sand-power Engine.—The large driving wheel consists of two circles of thick cardboard, each about 6 in. across, firmly glued together. These two circles are bevelled, and fixed facing inwards, so that a groove is left in which the power band can run.
Fig. 76.
Through the centre of the driving wheel thus fashioned a piece of dowelling or old lead pencil is fixed, projecting 1/4 in. on one side, and about 1-1/2 in. on the other. Nails are driven in the two ends of this axle, and the wheel is suspended between supports, glued and screwed firmly to a base board.
The flanged sand wheel is next constructed. For this, four oblong pieces of cardboard, 1-1/4 in. wide and about 2 in. long, are cut out. A line is scratched along each of these about 1/2 in. from the end, and the cardboard bent so as to form a scoop to hold the sand for an instant. These four flanges are then glued to the axle, and the side of the driving wheel. If the sand wheel so made is not sufficiently firm, then another small cardboard circle can be glued to the flanges, on the side remote from the driving wheel: this will strengthen the wheel and in no way interfere with the running.
All that is necessary now is to erect some sort of sand supply: for this a large canister will do. A tiny hole must be punched in the bottom of the tin, and a revolving trap made with another piece of tin. This is simple enough: all you need to do is cut a piece of tin about 3/4 in. long and 1/2 in. wide, and punch a hole in one end. This pierced tin should then be placed so that the unbroken end of the slip covers the supply hole. A forked rivet should then be passed through the hole in the slip and through the bottom of the canister and fixed in place (Fig. 77); the trap can then be made to revolve, and the sand supply started or stopped at will. The canister should be placed above the wheel so that a thin stream falls on the flanges and turns the wheel.
Fig. 77.