The rotor consists of a number of iron discs 2 J" in diq^meter



The Interrupter 47

and having twelve i^ holes drilled around the edge and a
y^g^" hole in the centre. They should be made of iron about
if oV ^^ thickness; about forty of them making a pile i"
high. These discs can be made by the coil builder with the
help of a lathe and drill press, or they can be obtained already
stamped out from any of the large dealers in electrical sup-
plies. A sufficient number of them are mounted on a shaft,
turned down from a f " rod of cold rolled steel to the size
shown in the figure, to make a pile 2 J" in height. As the
motor will not have a very heavy load thrown on it, it will
not be necessary to key them to the shaft. A good driving
fit is sufficient to keep them from turning. They can be
clamped in position by the nut shown in the figure. The
conductors consist of twelve f' copper rods 2 J" long. One
of these rods should be driven in each of the holes around
the edge of the discs and should project Y beyond them on
both sides. To short-circuit them, two heavy rings made
by bending two pieces of Y copper rod into a circle having
an outside diameter of if" are soldered to the ends of the
rods. Use sufficient solder in making these connections
in order to prevent heating at the connections by the induced
current in the rotor. This completes the rotor.
