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R/C Combat Vehicles

Homemade Torsion Springs

by
Doug Conn
I tried in vain to find a supplier of inexpensive torsion springs that would sell less than a couple million at a time, so I decided to try winding my own springs. The photos in this article show the tooling, the process, and a finished spring after trimming and stress relief. They came out pretty well, I think.

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Making these torsion springs was actually pretty painless. Just $22 got me enough spring wire from www.smallparts.com for 60 or 70 springs. The tools were very easy to make and easy to use once I got the hang of it.

I used the Torsion Spring Designer to help figure out what size wire and how many coils to use for my springs, with the resulting specs:

Wire diam:0.125"
Inner diam:0.75"
Torque: 13.6 in-lbs @ 30 degrees
27.5 in-lbs @ 60 degrees
50.0 in-lbs @ 90 degrees

The homemade tooling consists of a steel rod to form the desired inner diameter of the spring, a steel plate with a hole in it to hold one tail of the spring and the "winding bar" to hold the other spring tail. If you're handy with welding (or know somebody who is), the bottom two parts can be weld onto a plate and then bolted to a sturdy table. Or, you can securely mount them in a heavy duty vise as shown here.

Click Photo For Enlargement (93 Kb)

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Bend the end of the wire to fit into the holder to start forming the tail of the spring. We're making a clockwise spring in this case. I wound both clockwise and counter-clockwise springs for easy installation on either side of my tank.
The winding bar slides over the rod and catches the other end of the spring wire with the bolt. By pressing down lightly to keep the wire trapped, slowly rotate the winding bar around the rod to form one or more spring coils. I used four coils of 1/8" spring wire for this spring.

Click Photo For Enlargement (93 Kb)

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The springs have 180 degree ends to allow for a lot variation in the adjustment. They're pretty stiff. I probably could have used a smaller diameter wire and still been able to support a very heavy tank.

After bending the springs, the spring wire becomes less stiff because of the forming process. To make them tougher, I heated them for an hour at 500 degrees to finish the manufacturing process.