of small screws, by means of which the
strip is adjusted relatively to the wipe.

Fixing the Coil.--Cut a strip of tin 1-3/4 inches wide and 4 inches long.
Punch a couple of holes near one end, and nail this to the side of the
base, with its forward end 4-1/4 inches from the crank shaft. Pass the
strip over the coil, and bend it down towards the base. Drill a couple of
screw holes, and screw the other end down so that the coil is gripped
fairly tight.

Fixing the Plunger. Two small guides, G1 G2, are made for the plunger. The
holes through which the slide rod moves should be a good fit, and their
centres at the level of the centre of the coil. Screw holes are bored in
the feet.

Pass the plunger through the coil, and place the guides on the rod. Then
draw the plunger forward till 1/2 inch projects. Bring G1 close up to it,
mark its position, and screw it to the base. The other guide, G2, should be
1-1/2 inches away from the rear of the coil.

[Illustration: Fig. 38.--Plan of electric reciprocating engine.]

The coil and guides must be adjusted so that the plunger does not touch the
coil anywhere during a stroke, packings being placed, if necessary, under
coil or guides. When the adjustment is satisfactory, screw the coil down
tightly, and cut off any superfluous parts of the rod.

The Connecting Rod.--Bore a hole near the end of the plunger for a screw
to hold the rear end of the connecting rod. Pull the plunger out till 1-3/4
inches project, turn the crank full forward, and measure off the distance
between the centres of the plunger hole and the crank pin. Drive a couple
of wire nails into a board, and twist the ends of a piece of 1/20-inch wire
round them twice. This wire constitutes a connecting rod amply strong
enough to stand the pulls to which it will be subjected. Fix the rod in
position.

Adjusting the Wipe.--Turn the wipe, W, round until it makes contact with
B2, and, holding the crank shaft with a pair of pliers, twist the crank on
it till it just begins the return stroke. Then turn the crank to find out
how long the wipe remains in contact, and adjust the crank relatively to
the wipe so that the crank is vertical when the period of contact is half
finished. The length of this period is controlled by the set screws at the
free end of B2.

OTHER DETAILS.

The fly wheel may be a disc of wood.

Oil all the rubbing parts slightly. Connect T1 to one terminal of the
battery, T2 to the coil, and the ot