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250 THE BOY ELECTRICIAN

The t0p comers are beveled and notched to receive the
slider-rods. A circular piece of wood two and five-eighths
inches in diameter and three-eighths of an inch thick is
nailed to the inside of each of the coil heads to support
the ends of the cylinder.

The wooden parts should be stained mahogany or some
other dark color ,and finished with a coat of shellac or
varnish.

The slider-rods are square brass 3-16 x 3-16 inches and
seven and three-quarters inches long. A small hole is bored
near the ends of each, one-quarter of an inch from the edge,
to receive a round-headed brass wood screw which holds
the rod to the tuner end.

The sliders may be made according to the plan shown
in Figure 201 .

The slider is made from a small piece of brass tubing,
three-sixteenths of an inch square. An 8- 32 flat-headed
brass screw is soldered to one face, in the center. A small
strip of phosphor bronze sheet or spring copper soldered to
the bottom of the slider forms a contact for making con-
nection to the wire on the cylinder. A small “ electrose ”
knob screwed to the slider makes a neat and efficient
handle.

Two sliders are required, one for each rod.

The tuning coil is assembled as shown in Figure 203.
The cardboard tube is held in place by several small brass

nails driven through it into the circular pieces on the coil
heads.

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