Switch Machines at MLS

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Switch Machines at Maricopa Live Steamers

Here is the completed switch installed and operational.

Written by Al Ford
Photos by Jim Manley

The 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 it’s 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.
*Written by* Al Ford Photos by Jim Manley Read more about the switch control system: The Automation of Adobe City Join the DLS Yahoo Group Would you like to discuss the ideas in this article? Post a comment or question here.

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