XXI. A WATER MOTOR.

FIG. 105 is a perspective view of a simple water motor which costs little
to make, and can be constructed by anybody able to use carpenter's tools
and a soldering iron. It will serve to drive a very small dynamo, or do
other work for which power on a small scale is required. A water supply
giving a pressure of 40 lbs. upwards per square inch must be available.

We begin operations by fashioning the case, which consists of three main
parts, the centre and two sides, held together by brass screws. For the
centre, select a piece of oak 1 inch thick. Mark off a square, 7 inches on
the side; find the centre of this, and describe a circle 5 inches in
diameter. A bulge is given to the circle towards one corner of the square,
at which the waste-pipe will be situated.

Cut out along the line with a keyhole saw. Then saw out the square of wood.
A 5/8-inch hole is now bored edgeways through the wood into the "bulge" for
the escape, and in what will be the top edge is drilled a 1/4-inch hole to
allow air to enter.

[Illustration: FIG. l05.--Simple water turbine.]

Cut out the sides, and screw them on to the centre at the four corners,
taking care that the grain runs the same way in all three pieces, so that
they may all expand or contract in the same direction. Plane off the edges
of the sides flush with the centre.

The parts should now be separated, after being marked so that they can be
reassembled correctly, and laid for a quarter of an hour in a pan of melted
paraffin wax, or, failing this, of vaseline, until the wood is thoroughly
impregnated. Reassemble the parts, and put in the rest of the holding
screws, which should have their heads countersunk flush with the wood.

[Illustration: FIG. 106.--Water turbine, with pulley side of casing
removed.]

For the shaft select a piece of steel rod 5/32 inch in diameter, and 3 or
4 inches long; for the bearings use two pieces, 3/4 inch long each, of
close-fitting brass tube. Now take a drill, very slightly smaller in
diameter than the bearings, and run holes right through the centres of, and
square to, the sides. Both holes should be drilled at one operation, so
that they may be in line.

With a wooden mallet drive the bearings, which should be tapered slightly
at the entering end, through the sides. Push the shaft through them. If it
refuses to pass, or, if passed, turns very unwillingly, the bearings must
be out of line; in which case the follow