The Known is finite, the unknown infinite; intellectually we stand on an islet in the midst of an illimitable ocean of inexplicability. Our business in every generation is to reclaim a little more land.  -T.H. Huxley, 1887



This is one of my favorite projects. Ed Marriott built it, I helped him use it. Basically its using a really strong electronic magnet to launch a metal rod kind of fast. Don't play with this stuff if you don't know what your doing!

Shown above is the Coil Gun. The two large cylinders on the bottom are the capacitors, these hold the electric charge needed to power the magnet. On top of the capacitors is the glass tubing. This tubing holds the projectile. The coil is wrapped in black around the glass tube. When the electricity flows through the coil it creates a magnet field. In order to get the electricity to flow you need a switch, a big switch. The first one we tried we melted, so I made a big heavy duty switch which is shown above in the center.

The Coil Gun also needs projectiles. We tested all sorts of metals (steel, aluminum, bronze, copper and brass) and shapes. Steel worked the best, mostly because it has iron in it. Everything else pretty much didn't work at all.

We set the Coil Gun up in the basement and leveled it out. We then measured the height of the barrel relative to the floor. By knowing this information and then measuring the height that the projectile hits the target we can calculate the muzzle velocity.

We ran several tests the first bunch were rather unsuccessful. We finally got things working right and got some good results. We got up to 106 ft/sec at one time. Not bad for a first try. Shown below is our data. We measured projectile mass, the length it went and its drop. From this we can infer the muzzle velocity and kinetic energy.

Then as our second experiment we varied the initial position of the projectile relative to the coil. We found a sweet spot in the coil, the place that fired the projectile the fastest using the same input energy.

Here is a video of our coil gun adventures. Its kind of big. (Video 122 MB)

The next step is to make a 400V power supply and continue testing. Many variables can be changed here, projectile shape and material, coil characteristics, increased capacitors and voltage ratings, and more. My unofficial goal would be to make a gun that can shoot a projectile faster than the speed of sound. That mean about 10 times the speed and therefore 100 times the energy needed. In other words, I have a bit of work to do.

(NOTE: I've acquired a new 1.5 kV power supply, so I will be continuing the fun)



ŠEric Jacob