Barry's Coilguns


So ... how well does the Mark IV work?

The next few pages document the detailed measurements, graphs, and design method to arrive at the next coil size.


Photograph of workbench to measure speedSeveral different coil sizes were tested until the desired speed was reached, within limitations of peak coil current.

We started with a large coil and progressively removed turns. Obviously it is easier to remove turns than add them, but the primary advantage of this strategy is that the larger coils have lower peak current due to the higher inductance. This allows us to collect measurements before increasing the stress on the components.

For each coil, we measured velocity and used an oscilloscope to monitor coil current.

A voltage sweep was run on several different projectiles for each coil, adjusting the starting position for each voltage to reach maximum velocity. This was a lot of measurements and was a labor-intensive, time-consuming process.

  1. Coil of 97 Turns
  2. Coil of 84 Turns
  3. Burned Coil #1 of 56 Turns
  4. Good Coil #2 of 56 Turns
  5. Eddy Currents
  6. Sensitivity to Starting Position
  7. Conclusions
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