Instructables

400 volt RAIL GUN

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...
 
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Step 1: Parts

Most of this project can be changed, so you don't have to use these exact parts, but these are what I used for mine.

For the Compressed air system;                                                         (step 4)
             Gas reservoir- I used 4 small one, but a large single would be perfect, or use a spring.
             2 gas valves- 2 gives a faster rate of flow, but not necessary if using a spring.
             Pneumatics pipes- reservoir to valve to barrel connections
             Steel tube (barrel)- diameter must be similar but slightly larger than you projectile.

For electrical (the rail gun)
            I used 10 400 volt 450uf aluminium electrolyte capacitors (step 2)
            Solid aluminium bar (for rails)- 20cm x 3cm x 3cm              (step 3)
            Acrylic 20cm x 3cm x 0.2cm
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Tobor 2.01 year ago
you could use diodes for the problem of energy going back into the transformer issue you mentioned.
cubj712 years ago
hey if the projectile does not move try to hook up capacitors in parallel, so you get more microfarads. not in series.
The answer is... a paintball gun.

crazyjp got me thinking though... If you use the paintball gun as the initial means of propulsion and then build a rail gun around it, would it work? Like a "sleeve" that you bolt in place over the barrel with all the caps and wiring built in, all you will then need to do is find a way to activate the circuit automatically once the paintball gun has fired. You might have to cut down the barrel though, the standard barrel should be okay since they're mostly quite short and useless anyway.

The loading problem has also then been solved as most paintball guns are semi-automatic and have hoppers attached, all you need is a the correct diameter projectiles.

You might need some kind of separate battery-pack or else things will get real heavy. Unless you can find some small, light, long-lasting, high-voltage batteries.
crazyjp2 years ago
if your using compressed air wouldnt it be simpler top just take the compress air hose hook it up to a barrel that just barely lets your projectile slide through put a notch in the spot were you want to load the projectile adn get a piece of tube that will slide over the spot where you load the projectile ad have some type of triger that when pulled causes the compressed air to be shhot into the barrel forcing the projectile out the end of the barrel and just demolising what ever you were aiming at??? i mean sure making a rail gun would be bitchin but you would also have to deall with some type of power source that can create 400volts verse just an air tank you strap to your back and refill off of a 120 volt air compressor?? i dont know if im wrong when it comes to thinking that the gun would be lighter if its just powered off of compressed air than having a bunch of batterys and capaactiors and metal rails
techno guy2 years ago
Mine didnt work!!!!! I built one and charrged it up to 60 volts and I started it by rolling it and as soon as I applied the voltage, it stopped on the track. And it did that even when I reversed the polarity. How can I make it work?
akinich2 years ago
Hey dude nice instructable
i kinda need help asap!
i built a mixture of ur instructable and from how to make a railgun
i have 5 caps of rating 250v and 680uF each
that comes to about 3400uf
the rail type is from the other instructable
the main thing is that i am not able to fire anything
the voltages i used are from 7.5 to 12 v
i need help asap
oh yeah btw i used hack saw blades as rails ( removed the paint )
and no launch mechanism
thanks in advance!!!!
Akinich
indra8103 years ago
Hi....

I already trying to build one. But when i'm firing it, the ball bearing was not sped like your's.

In my design, i use two parallel aluminium strip and the gap between 2 rails is 2.1 cm and the diameter of the ball bearing is 2 cm. so,what i want to know is, does the ball bearing and the rail need to touch each other when it is fired ??


Thanks !!
minisojo (author)  indra8103 years ago
Preferably, yes, they need to touch, other it might not get a constant current flowing through, and there will be more arching, which will erode your rails faster and result in even less contact. It should work without them touching, as long as the current can jump the gaps, but probably not as well.
hahaha553 years ago
Hi

I'm trying to build one of these for a school project. I plan on only using a small voltage (30V), like the one in your video, but I am having a hard time finding the right capacitors.

What if I have 45 100uF 35v capacitors @30V? Would that be enough to mimic what I saw in the video with only 30V and 10 450uF capacitors?

Thanks!
I found cheap 390uF 200V Electrolytic Capacitors. Would these work in place of your 450uf 400V ones if I used 12 of them instead of 10?
minisojo (author)  hahaha553 years ago
Yep, they'll work fine. If you can find a higher power supply then things will really start to happen. Although, I think in mine, quite a bit of the speed came from the compressed air, so a higher voltage would work better and look much better. I'm just updating with my next new project i'm making for my A2 after the summer. yay
indra8103 years ago
Hi....

Right now, i am trying to build a railgun for my school project.

I want to know about the semi-conductor diode that you used for your project. What type it is ??

And for the rail, if i use two parallel copper strip (75 cm x 5 cm x 0.5 cm), will it work ??

Thank you before....
minisojo (author)  indra8103 years ago
Copper will work better than the aluminium I used, as for the diodes, I got mine out of a plug socket adapter for a mobile, but I think I have destroyed them with whatever I put through them, but, I think, although the ratings will be low, you can use diodes out of a plug adapter as your current will be much lower than the plug sockets, and even though your voltage will probably be much higher, they should survive, but I'm not completely sure. Or, for something simpler, use a rectifier instead of a diode, because they have a very high voltage and current rating, and I think you only need one to convert from AC to DC, but, you may want to check this before you try, because I could be completely wrong.
fjpalacios13 years ago
Working on it....thanks!
nadams-23 years ago
hey so i tried building a rail gun and all i got out of it was alittle plasma. okay, my question is will a 4 farad capacitor work in place of the 8 capacitors?
minisojo (author)  nadams-23 years ago
Hi. What voltage did you charge the capacitor with, as this will limit the power and length of time the capacitor discharges in, cause 4 farad is massive, but that sounds like a supercapacitor, which normally will not have a large enough voltage be as effective, or the other cause i can think of is that your projectile isn't entering the rails fast enough and is sticking to the rails as the electricity arcs between rail and projectile. Hope this helps a bit.
Reach3 years ago
What is the biggest thing you can shoot out of it? Or does it no shoot anything.
minisojo (author)  Reach3 years ago
You can make it to shoot any size (power and materials depending), but mine was firing 9mm ball bearings, but 6mm for my new one.
Rhanyc3 years ago
Hey, I'm actually quite eager seeing the video were you put 400 Volts through it. Is it coming soon or weren't you able to use 400 Volts?
minisojo (author)  Rhanyc3 years ago
Unfortunately, i had to take apart my rail gun to use the parts in the airsoft gun, but, I am putting it back togeather in the next couple of months, with a few additions, and with any luck, finish the power supply, it shouldn't take to long, and the power supply shouldn't be to much of a problem, so look back in a month and hopefully i'll have something to update this with. Sorry I haven't been able to do this sooner.
REA4 years ago
rather than an air compressor, cant you get away with using a spring to propel the projectile toward the rails?
minisojo (author)  REA4 years ago
Sorry i've been slow replying
A spring should be fine to use, the ball bearing just needs to be moving fast enough not to get welded to the rails.
The projectile I used was about 0.7 grams, but i'm not sure because the packet didn't say as most steel ballbearings aren't usually used as projectiles. Unfortunately I never got a chance to measure the velocity untill I needed the capacitors for my actually project, but in 3 or 4 weeks I should be able to give a speed for one firing a 6mm ball bearing with hopefully 400 volts.
Would you have a good idea whether higher capacity or voltage would produce higher velocity? I'm finding lots of 400 and 450 v caps, but to get up over 300uF starts getting expensive. I found some 10KuF 450V but I can't see putting $35 each into them. Suggestions?
REA odiekokee3 years ago
ive seen 9 F (9000uF) capacitors for about 10 dollars (forgot where though). you could try going to a computer part recycling place and salvage some capacitors from a motherboard. most of the time they will be somewhere around 2.2 F.
sandito REA3 years ago
uF mean micro farad or millionth so a 9 Farad cap would be 9000000uF
REA sandito3 years ago
thanks. my grasp on the metric system starts to dwindle after milli (cant quite process that many zeros).
minisojo (author)  odiekokee3 years ago
The higher the capacitance, the more energy it can store, so the higher the capacitance the longer it takes to discharge or the higher the charge given out. The voltage will be how high a voltage ytou can charge it with (it will give out the same voltage as it is charged, so buy capacitors with a voltage slightly higher than what you want to put in. My physics departement had a 400 volt power supply so I used 400 volts, but at the end they decicded not to let me test it with the full 400 volts). But a 300 uf 100 volt capacitor stores the same potential energy as a 100 uf 300 volt capacitor. But, befor you spend any money you may want to try and find a bit more out about capacitors so you buy what you need.
REA minisojo4 years ago
i plan on firing pennies, as they are coated with a diamagnet (copper), and also because they are abundant, cheep (1¢ per shot lol), and wont take to much force to get a decent speed, as it is light.
minisojo (author)  REA4 years ago
That sounds like a good idea, but making a tight fit barrel and when using a high voltage, stopping the electrical current jumping across the two rails might be more difficult, but that does sound awesome.
Speedmite3 years ago
I was thinking, use steel ball bearings that are 6mm and use an airsoft gun, but my problem is i dont know where to get the cameras. They ship them off at walmart, whitch leads me to belive other chain stores like walgreens are doing it too. So where did you get yours, and do I have to go to some odd camera store?

Blacks Cameras
minisojo (author)  Speedmite3 years ago
Unfortunately, I think most places now recycle the disposable cameras, so I think you will either have to buy a new disposable camera and take it apart, or build your own DC/AC converter. I didn't use cameras, I used a converter from a cathode tube light, unfortunately, this is a little more complicated as it produces over 2000 volts, and it still needs converting back to DC.
sandito3 years ago
the only place that doesn't get rid of old disposable cameras right away is blacks.

I called every camera store in Vancouver, Blacks was the only one with a box of them.

They said that they like to keep them to go and smash, so they gave me 20 for free

bartj3 years ago
A question and a comment.

1) How do you switch the power from the caps to the rails or are they always connected together?

2) Somewhere in the comments someone says:

"...But a 300 uf 100 volt capacitor stores the same potential energy as a 100 uf 300 volt capacitor...."

The actual formula for energy stored in a cap is 1/2 * C * V^2

300uf 100 v cap = 1/2 * .0003 F * 100 ^ 2 = 1.5 Joules
100 Uf 300 c cap = 1/2 * .0001 F * 300 ^ = 4.5 Joules

Thus, go for a higher voltage as the energy stored is related to the square of the voltage.
minisojo (author)  bartj3 years ago
The rails are always connected to the capacitors, the projectile is the thing that completes the circuit, and yep, forgot about that, thanks for the correction. It was my mistake, i hope it didn't cause anyone any problems.
adoesker3 years ago
oh and i don't recommend charging your caps to the rating, they like to explode, try a bit below for safety, if you go with ac-dc transformer system, they tend to get heavy, but if you do a quick fix is to take any household tranny get some high rated diodes you can rectify the ac to dc with 4 in a diamond shape.
adoesker3 years ago
If you have an e.p.o. in your area its great for power supplies, i got 4 dc-dc transformers from there- 12v to 75v, had a little battery pack, fed power to each in parallel, and hooked the outputs up in series giving me 300v to charge my 6 350v 4180uf caps, my coilgun ended up the size of a bazooka and blasted holes in my house doors much to my parents dismay, lol. I like the airsoft/rail combo. Don't give up!
Speedmite3 years ago
So getting 20 capacitors with chargers, each around 330v, and 100 uf.
How does that compare to yours, power-wise and could I shoot 4.5mm bbs?

Im using 2 rails, each .5x 6x .25 sandwiched between plexiglass with bolts

Was only planning on aluminum foil, but Idk.

Havent built it yet.
Also, the rails are steel. Would copper or steel bbs work better?
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