5/32-inch hole in the barrel on this line just below plate B, and a similar
hole in the bottom of the cylinder. (The cylinder end should be put in
position temporarily while this is done to prevent distortion.) Flatten
down the cylinder slightly on the line of the hole, so that it may lie
snugly against the barrel, and clean the outside of the barrel. Lay the
cylinder against the barrel with the holes opposite one another, and push a
short piece of wood through to exclude solder from the holes and keep the
holes in line. Half a dozen turns of fine wire strained tightly round
cylinder and barrel will hold the cylinder in place while soldering is done
with a bit or lamp. The end of the cylinder should then be made fast.

The Displacer.--This is a circular block of wood--well dried before
turning--5/8 inch thick and 3/32 inch less in diameter than the inside of
the barrel. The rod hole in it should be bored as truly central as
possible. A hole is drilled edgeways through the block and through the rod
to take a pin to hold the two together. To prevent it splitting with the
heat, make a couple of grooves in the sides to accommodate a few turns of
fine copper wire, the twisted ends of which should be beaten down flush
with the outside of the block. The bottom of the block is protected by a
disc of asbestos card held up to the wood by a disc of tin nailed on.

The Crank Shaft and Crank.--The central crank of the crank shaft--that
for the displacer--has a "throw" of 1/4 inch, as the full travel of the
displacer is 1/2 inch. If the bending of a rod to the proper shape is
beyond the reader's capacity, he may build up a crank in the manner shown
in Fig. 101. Holes for the shaft are bored near the tops of the supports,
and the shaft is put in place. After this has been done, smoke the shaft in
a candle flame and solder two small bits of tubing, or bored pieces of
brass, to the outside of the supports to increase the length of the
bearing. The power-crank boss is a 1-1/2-inch brass disc. This crank has a
"throw" of 1/2 inch.

[Illustration: FIG. 101.-Details of built-up crank.]

Connecting Rods.--Put a piece of card 1/16 inch thick in the bottom of
the cylinder and push the piston home. Turn the power crank down and mark
off the centre of the hole for the crank pin in the connecting rod CR2.
Solder a piece of strip brass on each side of the rod at this point;
measure again, and drill.

The top of the displacer rod D is now fil