The Frame.--Having got the motor wheels adjusted, shorten E so that it
projects 2 inches beyond the centres of the axles at each end. Two cross
bars, GG, 3-1/2 inches long, are then glued to the under side of E,
projecting 1/8 inch. To these are glued two 3/8-inch strips, FF, of the
same length as E. A buffer beam, K, is screwed to G. A removable cover,
abedfg, is made out of cigar-box wood or tin. The ends rest on GG; the
sides on FF. Doors and windows are cut out, and handrails, etc., added to
make the locomotive suggest the real thing--except for the proportionate
size and arrangement of the wheels.
Electrical Connections.--The current collector, CR, should be well turned
up at the end, so as not to catch on the centre rail joints, and not press
hard enough on the rail to cause noticeable resistance. The fixed end of CR
is connected through T2 with one brush, B, and both wheel bearings with T1.
[Illustration: FIG. 48.--Reversing switch.]
Electrical Fittings.--The best source of power to use is dry cells giving
1-1/2 to 2 volts each. These can be bought at 1s. apiece in fairly large
sizes.
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