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How to create a electrical gun, the Coilgun!


Coil guns operate on a force of energy called Joules. You can convert joules into any force of energy, such as horse power, etc. The basics of a coil gun operate by storing a lot of Joules in a capacitor. The best way to generate a lot of Joules, is to use lots of voltage and capacitance in capacitors. We are talking on the range of 300+ Volts. The formula to calculate how much joules something has by relating voltage and capacitance is:

 J=0.5*V^2*C

 

J= Joules

V= Voltage

C= Capacitance in Farads

 

This means that if you had 100 Volts and a 1000uf capacitor, you would have 5 Joules of power, which is not a lot. If you were to boost the voltage to say, 300 Volts and 1000uf capacitor, the power would be 45 Joules. Thats a sinifigant increase in power! That's because voltage is exponental. It is a common practice to increase voltage by sacrificing capacitance. Here is an example:

 

45=0.5*300^2*0.001

 45= Joules

300= Voltage

0.001=1000uf, but it had to be in a F format so you add a few zeros before it.

 

That above was a control. We will now decrease the capacitance by half, and increase the voltage by double. We do this by simply adding the capacitors in series, like so: -||--||-

Here is the increase in power

J=0.5*600^2*0.0005

90= Joules

600= Voltage

0.0005=500uf

 As you can see, by increasing Voltage by sacrificing half of the capacitance doubles the output power!

 

for more on coil guns, you can go to wikipedia for more on coilguns.

 

Ok now for the good stuff!
 
Most if not all single stage coil guns (multi stage coil guns cost too much so stay out of them) consist of these 4 basic things:
  • Barrel/Coil
  • Capacitor Bank
  • Trigger
  • Charge Circuitry

The Barrel/Coil is made up of many many coils of wire that the discharged capacitors flow through, producing a massive amount of electromagnetic flux, that effectively attacts the ferromagnetic projectile and propelling it through and past the coil.

The Capacitor bank holds the massive amount of energy previously described (Joules). A very cheap source of these capacitors can be found in disposable cameras. The capacitors can have a rating from 80uf+ and 300V+, making these a great source for capacitors.

The Trigger can be anything from a switch to a SCR (Scilicon Controlled Rectifier). A SCR is prefered, because using a mechanical switching method can easily melt the contacts. This is a very common problem, therefore scilicon switching is vastly superior.

The Charge circuitry charges the capacitors, and depending on the milliamp output of the circuitry, it could take anywhere from a few seconds to a few minutes. There are many variables on charging, but the best place to aquire cheap charge circuits (with a low charge rate) is found in disposable cameras.

 

(UPDATE SOON) 

Charging Circuit 

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Nebster's picture

im in the process of making a coil gun. im using an old bronken flash flood super soaker as my shell.

its gonna e nasty.

TheOther1's picture

Here is a nice example of a portable coil gun.

http://www.thinkbotics.com/military.htm