Coilgun Basics

Coilgun Basics

I had my first experiences with coilguns as a child when I played with an old doorbell, more precisely, with a so-called Bim-Bam gong. This gong consists of a coil with a movable, spring-loaded core and is similar to a solenoid. You can visualize how it works in this video.

Of course, I immediately came up with the idea of removing one of the metal plates so that the core inside could move freely…

What is a Coilgun?

A coilgun operates on a similar principle. A movable core is accelerated by one or more coils by cleverly switching the coils on and off.

A movable iron core is positioned in front of the coil (see Figure 1). When we switch on the current, the coil attracts the iron core, causing the center of the core to move towards the center of the coil.

The force generated depends on several factors:

• The current flowing through the coil.
• The number of turns of the coil.
• The dimensions of the coil.
• The dimensions of the iron core.
• The distance from the core to the coil.

Here’s a small Java applet to illustrate the concept: Clicking on the simulation activates the coil, and the black projectile is attracted. Releasing the mouse button turns off the coil. Trying to accelerate the projectile by skillfully controlling the coil is not as easy as it sounds.

To reset the simulation, simply press the “R” key on your keyboard.