I took a detour into the land of magnetic uncoupling for a while. First I started with the Radio Shack rare earth magnets as recommended many places on the web. They work too well! I found that not only do they attract the coupler's trip pins, they strongly attract my metal wheelsets as well! This created a problem at the Firebaugh Crushed Stone spur when pulling cars over the magnets. The magnets would attract the metal wheels of the trailing car and pull it forward. This created a slinky effect that got more and more pronounced the more cars were pulled across them. Not only did it look bad, it caused considerable unintentional uncoupling - the fourth car was gauranteed to be dropped!

My second thought was to try electromagnets. I could turn these on only when uncoupling was needed and when off they would not attract my metal wheelsets. Making magnets strong enough proved challenging. I finally "succeeded" with 6 layers 1½" long of #30 gauge magnet wire wrapped on a 2" length of #6-32 bolt stock; using two of these wired in series and mounted on a steel plate to create a horseshoe electromagnet. They worked, provided the tops of the of the magnets contacted the bottoms of the rails (meaing the ties had to be cut away). But they were still not as strong as the rare earth magnets, drew a lot of power (1.1 amps at 12VDC) and got very warm if left on too long. Mounting them was challenging since I already had the track layed and ballasted. I ruined a bit of track by drilling up from under the layout to a diameter of 3/8"! Not fun.

Finally I realized that all I needed was a simple mechanical method of moving the rare earth magnets up and down below the track so that when down they were far enough away from the track to not affect the trains. A tortoise switch machine provided the mechanism for doing so, all I added to it was a peice of angle bracket and two 10-24 bolts to push the magnets. Using steel bolts, the magnets just stick to them and I used @frac14;" brass tube pushed through the sub-roadbed to allow them to slide up and down. Voila! An uncoupling machine is born!

Click small image for larger view.

Radio Shack rare earth magnets

Magnets placed under the track

Wrapping an electro magnet

First layer complete.

Complete magnet

Horseshoe electromagnet.

Uncoupling machine

Uncoupling machine

Mounting site for uncoupling machine

Mounted uncoupling machine