Coilgun Knowledgebase

Let's start with a warning: Don't try this if you have no idea what you are doing. Coilguns often run on high voltages so there's a pretty great chance you'll get electrocuted. I am not responsible for any injuries.
HOW TO BUILD A COILGUN


A coilgun or gaussrifle is basically an electromagnetic linear accelerator. Coilguns use, as the name says, a coil in order to create a magnetic field 
- it's a different setup than a railgun!

A coilgun allways consists of these three basic components:

A coil made out of insulated wire.
(The wire used may look like bare copper wire, but it is enamelled wire).

A capacitor or a comparable high electric current energy source. 

Last but not least, a switch which connects the energy source to the coil. This could be a normal power switch, but since most coilguns have high currents I recommend using a thyristor.

How it works:
We have a coil wound over a non-conductive tube which is the coilgun's barrel, of course. It has to be non conductive (plastic or something comparable) because otherwise the coil's magnetic field would simply cancel out itself inside the tube. The projectile has to be made of a ferro magnetic material, that means stuff that reacts to magnetic fields.
If a short current pulse is passed through the coil via our charged capacitor and the switch, the projectile will be pulled into the coil. If the pulse ends before the projectile gets to the coil's middle, it'll leave with a gain in velocity. The main difficulties with coilguns are winding an appropriate coil, finding the appropriate voltage and capacity and of course timing and positioning of the projectile. 
Here is a short animation of the magnetic field when a projectile enters the coil:
The more windings a coil has, the stronger is its magnetic field. But if you use too long and thin wire with your coilgun, either the wire will eventually burn through or the coil's electric resistance will go up and lower the current and thus weaken the magnetic field. 
My test circuit looks like this:
I charged the capacitor with a little transformer circuit taken from a disposable camera's flash.
If you don't know how to charge a capacitor click here.
There's a test video, too:  
Further increasing of the velocity is possible by adding more stages which means not more than adding more coils. These coils need to be triggered automatically since the projectile is already in motion and you're not able to push the button at the right moment. Many people use light barriers mounted in front of the second stage. Here's a schematic of my second stage light barrier trigger (Ignore the safety switchtes and safety lights):
And here is a video demonstration:  

You can see the second stage, a light barrier in front of it and a little screw which gets pushed (normally it would fly through by itself due to the first stage) into the beam. I built this two staged test rig with multiple measurment devices in order to learn more about positioning of the projectile in front of the coil, the coil itself, capacity and voltage and timed triggering.

There are a lot of safety switches and control Leds just because of safety matters. Voltage range is from 0-400V and one stage has a capacity of 4400uF. I used several projectiles of different heaviness.
With a little positioning devive I was able to test out many starting positions.
Due to a second measurement coil I was able to record the indirect magnetic pulse of the first stage firing. The other two peaks are for velocity measurement.


What are coilguns capable of?

 Coilguns are scalable to very large applications, possibly as large as a mass driver to put payloads into orbit.It has no moving parts thus there's the magic of invisible forces at work. It requires no special construction techniques or unusual tools. The coilgun technique can also be used to build so called levitrons which are "no gravity hovering devices".

31 comments:

  1. loving the knowledge base...

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  2. Awesome. Thanks for sharing all this.

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  3. I have a couple ideas that might get you better velocity. returner@paxaran.com

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  4. thats rturner@paxaran.com

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  5. Great instruction on how coilguns operate! If multiple coils were used, for example...lets say 10, the distance between each coil would have to be increased as the speed of the projectile increases, correct? Would it be feasible for each coil in a multiple coil gun to have its own power source instead of having one huge power source to operate it? Also, would it be helpful to have spiral grooves or something similar to that found in firearm barrels in order to stabilize the projectile in flight?
    Thanks!
    juantenoriojr@yahoo.com

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    1. Instead of rifling your barrel, which would require you to be able to machine your barrel, you could fin the projectile.

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    2. another issue with riffling the barrel is the increased drag on the projectile. although I'm fairly confident that that's easily remedied by increasing the power of the electro mags(coils). i don't see a problem with using separate power sources for each electro mag, but im not too sure, dont have alot of experience with them. i would think that using one power source for multiple electro mags would cause voltage drops farther down the line resulting in longer charge times. but idk for sure.

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  6. So cool, but i bet i would be too young to operate this.

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  7. All of this is just amazing, it was so incredibly helpful for getting me started on my own project. what would be really helpful is adding a section on efficiency. By this i mean information on stuff like the best way to make the coils and where to put the projectile. Thanks!

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  8. I just killed my dad.

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  9. can you tell me where i can find the tube that you made the coil with? i dont know where to search for that small diameter tubes..

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  10. i mean the barrel

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  11. http://www.amazon.de/Polycarbonat-Rohr-%C3%B8-10-1000/dp/B00AEOFF02/ref=sr_1_2?ie=UTF8&qid=1361800041&sr=8-2

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  12. seems like one could make a larger coil gun by using high energy permanent neodymium magnets as a power source then maybe a spring mechanism to get to projectile from the clip or ammo holder to the barrel and get it moving initially. maybe Ive seen similar power rails like this done with a set of magenets all at a set angle creating a channel in an elongated V shaped channel then pushing a small ball bearing into the fields. could this be feasible?

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  13. Replies
    1. I think it was 8mm inner diameter and 10-12 mm outer diameter!

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  14. Couldn't you use sphere neo's as the projectile and use a reed switch between each coil so when the sphere passes the reed switch the next coil fires to draw it?

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  15. Did you ever tried to use neodymium ball magnets as ammuniton? Maybe the reaction to the coil could be stronger incresing the end speed as a result.
    Or maybe it's just stupid...

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  16. have you done a range test? how many fps shot?

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  17. Nice set up. For multiple coils; if the projectiles are of the same weight a timing circuit may do instead of sensors. Fins or spin? Tough making rifling that will last on a barrel that is non-metal and fins take extra room in the barrel or an X shaped bore with coils to shape... perplexing. Still I'd rather see a working coil gun than a rail gun since rail guns require rail to projectile contact and burn the rails. So many considerations with windings, capacitance, voltage, discharge time/timing. Probably why I haven't seen a really awesome coil gun yet. I would like to know how long it would take to charge the capacitors/firing cycle rate for a 30 grain projectile at 1100 fps should that setup ever be made for a 110v/30amp AC outlet.

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    1. curentley working on a 5.25 nato projectile and using a bolt action for loading a full copper jacket round and making ether the coil longer or as previous stated making a malty stage coil system i am currently working on the Physics and the new increased voltage i would be interested in knowing what was the pojectile you were using

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  18. Are you Deutsche? Also couldn't you use that 3d printer I've seen you use on some video to make an outer casing for a small iron ball bearing? So then you could have rifling on the bullet instead of the barrel, it could just have an open back so you could pop in the ball bearing. Some times on lead pellets they have the opposite idea with popping the bb in the front.

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    1. the projektile needs to be ferromagnetic so the coils can suck it

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  19. Hi.My name is Pramual Worapap. Please call me Mee. My Country Thailand. I want to build Coilgun. It interesting. But I do not understand. Because I a litle readinng,meaning,speaking english I want Circuit Coilgun 2 or 3 coil and all equipment list. (Sorry if word wrong) Thank you very much.

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  20. Have you made any critical findings of 2nd and 3rd stage coil design which optimise the speed? I have found that the trigger pulse signal for the later stages has to be a shorter pulse and has to be larger in amplitude to be more effective...Also I believe its better if 2nd and 3rd coil have less turns?

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    1. Sorry I forgot, but I'm asking everyone if they have any helpful input or advice to what I am asking to please if they could contribute, thanks all.

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  21. Which Transformator do you use?

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  22. Thanks for sharing this...

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