Barry's Coilguns

Winding Coils

How do you wind a coil for a coilgun? How can you make coils with consistent properties?

Magnet wire allows you to pack the most number of turns in the smallest space -- many more than hook-up wire. Other wire types have thicker plastic insulation to protect it from bumps and other hazards. Magnet wire has very thin insulation, and usually assumes you will protect it from Real Life.

Where to Buy Magnet Wire

You can find magnet wire at surplus or industrial supply stores. Sometimes, you can buy this wire at electrical motor repair shops. Just be prepared to buy it in a 15-lb spool. Sometimes partial spools are sold to surplus stores. In Bellevue, WA, you can find partial spools at Vetco Electronics. In downtown Seattle you will find a larger selection and lower prices at Radar Electric.

Making Coils

I wound my coils by hand onto a coil-winding jig. Take these ideas as a starting point and adapt to your own situation.

I've heard some people recommend you treat the finished coil by dipping it in Glyptol. I used a little SuperGlue to help hold the ends together.

By the way, I tried spinning the coil jig on an electric drill, but couldn't lay down windings tightly enough together. For the most compact windings, I had to put them on slowly and carefully by hand.

What size of tube should you choose? What size of coil? Read here.
What kind of projectile works best? Read here.

Coil Winding Jig

Use a four-inch carriage bolt of the right diameter to fit into the coil gun tube. Cut a piece of tube the same length as the desired coil -- this will support the inside of the coil. Later, you will slide the coil off from this form onto the final firing tube. How can you make it easy to slide a tight coil off from the winding form? Cut some notebook paper to this width, and wrap two thicknesses of paper onto the form before you start winding. This provides just enough additional inside diameter to the coil, so you will have an easy sliding fit onto the firing tube.

Photo of coil winding jigUse big flatwashers as the sides to support the ends while winding. They keep the sides of the coil flat and even. Put lockwashers outside the flatwashers to keep the flatwashers from turning. (See the photo at right.)

Drill a small hole, big enough for the wire, through one of the lockwashers. This will be the starting point for the first layer of wires on the inner-most side of the coil.

After winding every other layer, wrap it once with cellophane tape to hold the wire in place and provide a smooth base for the next layer. After winding the coil, I dripped some SuperGlue onto the exposed flat ends to help keep the windings from spreading or snagging.

I want to be able to slide a new coil off the jig, and slide it onto the coil gun tube. To get the right fit, wrap two layers of notepaper around the jig tube before winding. Then wind it as tight as you can. Remove the paper after the coil comes off. This gives you a few thousandths of an inch clearance, for that loose sliding fit onto the final coil tube.

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