For this instructable I will explain how to make a simple rail gun, firing metal ballbearings. However, the parts are not to expensive, but im not sure of how much it all came to as I built it at my school during DT lessons. There are more powerful versions, but this doesn't take long to build and is quite effective.
It is not very neat, but I didn't have much time as it was only meant to be an alternative way of building an airsoft gun using a new system (part of my GCSE project). My design fired 9mm steel ball bearings, which is fun, but can cause injury.
This does use voltages upto 400V, and comnpressed air, so be carefull, and never put anyone at risk from whatever you manage to create.
The railgun is a form of linear accelerator, using a electromagnetic force to propell an object. The way that these work is that a electrical current is conducted up one rail, across the projectile, and then back down the other rail (see picture). This is called the Lorenz force.
Please ask if you have any questions.
This is my first instrucatble, so please be nice...