Colin's 2 KJ coilgun
Number of coils: 1
6 Capacitors. Each capacitor is rated for 450 Volts DC and has a capacitance of 2400 uF.
Total capacitor bank energy
1.944 Kilojoules. For all intents and purposes, I'm going to refer to this as my 2 KJ coilgun. After testing and consideration, I decided to later remove two capacitors and save them for building a second coil later on. You can read more about the results and drop in efficiency in my results page.
The triggering mechanismAs you can see in the picture above, I use a very different approach for controlling current for my coilgun project. It is not easy to control over a thousands amps of current and hundreds of volts. Most people use SCRs, or silicon controlled rectifiers, however I decided to use devices known as contactors. Contactors are electromechanical relays designed to control massive amounts of electricity. The two pictured above are especially large. Because these are so expensive, it's very wise to try to find these on eBay. The contactor on the leftis rated for 800 amps continuous at 60 VAC. This was specifically designed for and sold to a nuclear power plant in Ohio. The contactor to the right is rated for 1000 amps continuous at 60 VAC. Now, because these are mechanical switches, there is some wear and tear associated with these devices. Each contactor has four silver contacting pads, which are slighly burned each time the switch is closed when the voltage is over 350 volts. However, this has not yet degraded the performance of my coilgun, which has been shot hundreds of times. Unfortunately, I do not recommend using a contactor for a second or third stage. The reason for this is because, like all mechanical switches, there is a fairly large amount of time needed to close the switch. It take sabout 10 milliseconds for either of these switches to close. Of course, for the first stage of a coil gun, it doesn't matter.
The CoilsMany coils were built and tested. Overall, the best coil constructed is four layers deep, 7.5 centimeters long, and uses stranded 14 gauge wire. For more information about the various coils used in this project, be sure to check out this section! For good information as to exactly how to construct these coils easily and quickly, this is a great source of information.
The BarrelThe barrel is constructed of compressed PVC tube. The outer diameter of the tube is 5 / 8 " and the inner diameter is 7 / 16 ". The barrel is just under two feet long.
The projectileThe projectile for this project is very simple, effective, and *extremely* easy to make. The projectils weighs 27 grams and is simply constructed out of a machine bolt and nuts. These are easily available from stores like Home Depot and Lowes. For more information about how the projectile mass affects final projectile energy, be sure to check out the projectile page!
Here, you can see the entire setup. Pictured are the power supply, capacitor bank, the contactors, the barrel, coil, and velocity detector! This is the complete setup for my coil gun.
Coilgun projects can be extremely dangerous if you don't know what your doing. Capacitors can unleash massive amounts of electricity which can seriously injure or kill. Please use this information with caution, as I can not be held responsible for your actions.