available they did not
provide enough voltage
swing out to the nomi-
nally 12-volt motors.
As an aside, I did con-
sider re-motoring with
6-volt motors but found
success before I had
to resort to this. I am
now considering using
a 6-volt or even a 3-volt
motor in the original
Roundhouse Boxcab
mechanism, even with
its poor power trans-
mission. The H-Bridge
designs usually solve
the problem of using a
single voltage source to
power a DC motor both
forward and reverse. I
even tried using a dis-
crete FET H-Bridge with
poor results. Success
came via a throwback! I
used an electromechan-
ical relay as a double-pole double-throw switch, just like DC
power packs typically use. The problem was the typical relay
would constantly draw power in its activated state, decreas-
ing battery life.
20. Repairing gears.
20
21
21. Wrapping the axle.
