The On-Line Magazine
of Rideable Model Railroading
August 19 2007
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Switch Machines at Maricopa
Here is the completed switch installed and
Photos by Jim Manley
Maricopa Live Steamers realized early on that if we were going to have passenger
and freight yards reached through a complex throat, we would need an easy and
fast way to line the switches to the proper route. There are five branches fed
by these yards and as many as ten turnouts must be lined for a train to enter or
exit correctly. Our plans called for 24 powered turn outs so we would need to
try and keep the costs down. The only throw mechanisms on the market at that
time were complicated, finely machined electric coil powered and could not be
thrown by hand unless the coil motor was unscrewed and disconnected. We tested a
pneumatic system but decided against it because of the cost and labor involved
in installing and maintaining the air supply tubing runs, some of which are 300
feet from the interlocking tower.
A power screw drive makes a great power unit for a switch.
First remove the handle and batteries.
|One of our members came up with the idea of using
old battery powered screwdrivers that people had discarded because the batteries
would no longer hold a charge. A screw type mechanism was built and would have
been fine except for the fact that is could not be hand thrown without
disconnecting the electric drive. We then wondered if we could connect the shaft
of the motor directly to the end of the shaft of the throw mechanism. Most of us
felt that this would be impractical because it would be far too much of a strain
on the small gears inside the screwdriver. However, we welded a 1/4 inch socket
directly on the end of the throw bar shaft then using the screwdriver bit, which
happened to be 1/4 inch, we connected the motor to the throw bar.
Here's another battery powered screw driver used. This one as a
different pivot system than the one above. After a modification, it's
ready to install.
|The motor had been prepared by removing the
batteries, battery housing, reversing and on and off switches. The wires that
come out from the motor were then connected to a two prong polarized plug. When
the battery housing was removed it left a nice large hole in the back of the
motor housing. The machine was then screwed down to a piece of 2 x 4 that had
been connected by angle brackets perpendicular to the throw shaft. The electric
motors are D.C. permanent magnet and are reversed by simply reversing the
polarity of the feed. The motors are rated at 4.5 volts but we have used as high
as 12 volts for very short periods and have had no problems. You would have to
decide on the best voltage depending on the length of your wire runs.
Here's the screw driver (seen above) mounted to the switch throw.
The switches can be controlled either electrically from the
tower or throwing the bar by hand. In the event of a burnout or other problem,
the switch motor can be unplugged and changed in a matter of minutes. Even
though itís difficult to believe that this system would be practical, many of
our machines are now in their fourth year of operation with over 3,000 throws
and are still working reliably.
Add a cover cut from a large pipe and you're in business.
Photos by Jim Manley
Read more about the switch control system:
The Automation of Adobe City
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