The other end of the cord is tied to the
switch handle so that when the alarm goes off the switch is either
opened or closed, depending on whether the cord is passed over
pulley C or pulley D.
When the cord is passed over pulley C, as shown in Fig. 1, the
circuit will be closed when the alarm goes off, but if it is
passed over D the circuit will be opened. Pulley D is fastened to
a piece of spring steel, E, which in operation is bent, as shown
by the dotted lines, thus causing the switch to snap open quickly
and prevent forming an arc.
--Contributed by Douglas Royer, Roanoke, Va.
[Illustration: Will Open or Close Circuit as Desired]
** How to Make a Rotary Pump [81]
[Illustration: Details of Rotary Pump]
A simple rotary pump is constructed on the principle of creating a
vacuum in a rubber tube and so causing water to rise to fill the
vacuum. Figs. 3, 4 and 5 show all the parts needed, excepting the
crank and tubing. The dimensions and description given are for a
minimum pump, but a larger one could be built in proportion.
Through the center of a block of wood 4 in. square and 7/8 in.
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