The wheel rails are made of carefully straightened brass strip 3/8 inch
wide and 1/16 inch thick, sunk rather more than 1/8 inch into wooden
sleepers (Fig. 42, a), 3-1/2 inches long and 3/4 inch wide (except at
junctions). The sleepers are prepared most quickly by cutting out a strip
of wood 3-1/2 inches wide in the direction of the grain, and long enough to
make half a dozen sleepers. Two saw cuts are sunk into the top, 2 inches
apart, reckoning from the inside edges, to the proper depth, and the wood
is then subdivided along the grain. The saw used should make a cut slightly
narrower than the strip, to give the wood a good hold. If the cut is
unavoidably too large, packings of tin strip must be forced in with the
rail on the outside. To secure the rails further, holes are bored in them
on each side of the sleeper (see Fig. 42, c), and fine iron or, brass wire
is passed through these, round the bottom of the sleeper, and made fast.
[Illustration: FIG. 43.--Tin chair for centre rail of electric track.]
The centre rail is soldered to small tin chairs, the feet of which are
pinned down to the sleepers.
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