Barry's Coilguns

Coilgun Mark II Construction

Coil physical dimensions My second model, the Mark II, has a coil with 18 gauge (1.06mm diameter) magnet wire wrapped in 14 layers. Since timing is so dependent on inductance, every other layer is tapped with a connection point. Trying with various connections will easily find the best performance. Unused turns were left open, although it's possible that shorting them would improve the magnetic field.

Iron washers (four each, about 8mm thick total) are placed at both ends of the coil to improve the magnetic field strength, and to guide the field toward the projectile. According to our theory page, this should help. In practice, look at the results here.

The projectile is 1.5" length (38mm) cut from steel rod labelled "Welding Steel - Round (C.R.)" which is 1/8" nominal (3.00mm) diameter.

The tube is a 25cm of "Brass Round Tube" labelled as 5/32" diameter (3.75mm actual inside diameter). Hookup wire is stranded 18ga, mostly doubled over the main current-carrying path.

In subsequent tests, I found that brass is a poor choice because it is conductive and loses energy in eddy currents.

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