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.
** Controller for a Small Motor [42]
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
[Illustration: Reverse for Motor]
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.
Pages:
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112