Instead of dry cells or accumulators a small foot or hand operated
dynamo generating direct, not alternating current, might be used. Its
life is indefinitely long, whereas dry cells become exhausted with use,
and accumulators need recharging from time to time. On occasion such a
dynamo might prove very convenient.
Anyone who possesses a fair-sized stationary engine and boiler might
increase the realism of the outdoor track by setting up a generating
station, which will give a good deal of extra fun.
XIV.
A SIMPLE RECIPROCATING ENGINE.
Figs. 51 and 52 illustrate a very simple form of fixed-cylinder engine
controlled by a slide valve.
An open-ended “trunk” piston, similar in principle to that used in gas
engines, is employed; and the valve is of the piston type, which is
less complicated than the box form of valve, though less easily made
steam-tight in small sizes. The engine is single-acting, making only
one power stroke per revolution.
The cylinder is a piece of brass tubing; the piston another piece of
tubing, fitting the first telescopically. Provided that the fit is true
enough to prevent the escape of steam, while not so close as to set up
excessive friction, a packing behind the piston is not needed; but
should serious leakage be anticipated, a packing of thick felt or
cloth, held up by a washer and nuts on the gudgeon G, will make things
secure. Similarly for the built-up piston valve P may be substituted a
piece of close-fitting brass rod with diameter reduced, except at the
ends, by filing or turning, to allow the passage of steam.