railgun
dixie43, Wed Mar 28 2007, 12:08AMI used a disposable camera to charge up five capaciters (60v and 80 micro faradays each) connected in parallel to two steel rails. The steel rails are parallel side besdie sandwhiched in between two pieces of plexiglass and bolted together. The metal rails are 16 inches long each. The end of the rails where the projectile is supposed to shoot out are parallel however the other end connected to the capaciters is not completely parallel. I was able to charge the capaciter bank however, when i turn on the switch to connect the capaciters to the rails i only get a large spark in between the rails where my projectile is (piece of tin foil in a U shape). I can't figure out why the tin foil won't shoot through the rails and only spark at the area of the projectile. This is my first time making a railgun and i am a high school student working on an electromagnetic physics project and have only done about 5 hours of research on railguns, so please forgive me if i ask dumb questions. I have to have the railgun finished by april 16.
Re: railgun
Michael W., Wed Mar 28 2007, 12:23AM
Either the tin foil could have vaporized or the capacitors don't provide near enough power to get the results your looking for...
Michael W., Wed Mar 28 2007, 12:23AM
Either the tin foil could have vaporized or the capacitors don't provide near enough power to get the results your looking for...
Re: railgun
dixie43, Wed Mar 28 2007, 12:28AM
I have a total of 400 micro farads and 300 volts in the capaciters and the tin foil was still intact. Do you have any suggestions to how i can make this work.
dixie43, Wed Mar 28 2007, 12:28AM
I have a total of 400 micro farads and 300 volts in the capaciters and the tin foil was still intact. Do you have any suggestions to how i can make this work.
Re: railgun
Bjørn, Wed Mar 28 2007, 12:37AM
Sparks means heat, heat means high resistance. Steel rails also means high resistance so your current is possibly too low.
You should put a lot of work into getting a very cood connection to the rails, maybe even use a spring mechanism to make sure the connection is close to perfect.
Connecting the capacitors in series to increase the voltage might increase the current, it depends on the ESR of the capacitors.
Bjørn, Wed Mar 28 2007, 12:37AM
Sparks means heat, heat means high resistance. Steel rails also means high resistance so your current is possibly too low.
You should put a lot of work into getting a very cood connection to the rails, maybe even use a spring mechanism to make sure the connection is close to perfect.
Connecting the capacitors in series to increase the voltage might increase the current, it depends on the ESR of the capacitors.
Re: railgun
dixie43, Wed Mar 28 2007, 12:47AM
Connecting the capacitors in series will definetely increase the voltage but, it will decrease the amount of energy i can store. Could you please explain the spring mechanism to me.
dixie43, Wed Mar 28 2007, 12:47AM
Connecting the capacitors in series will definetely increase the voltage but, it will decrease the amount of energy i can store. Could you please explain the spring mechanism to me.
Re: railgun
Billybobjoe, Wed Mar 28 2007, 01:18AM
300 volts and 400uf isn't possible with your current setup of five 60v, 80 uf capacitors. Which is it? Even with 300v, 400 uf, thats only 18 joules. I'm not an expert with railguns, however most people use energies in the KILOjoule range. Yours could still work, but will probably have to be more efficient than larger models to yield appreciable results.
I think what Bjorn means by spring mechanism is something that will give your projectile (which currently is probably the worst possible thing to fire) constant mechanical contact and therefore the least amount of resistance to your rails. I don't really know how to make that much clearer.
Billybobjoe, Wed Mar 28 2007, 01:18AM
300 volts and 400uf isn't possible with your current setup of five 60v, 80 uf capacitors. Which is it? Even with 300v, 400 uf, thats only 18 joules. I'm not an expert with railguns, however most people use energies in the KILOjoule range. Yours could still work, but will probably have to be more efficient than larger models to yield appreciable results.
I think what Bjorn means by spring mechanism is something that will give your projectile (which currently is probably the worst possible thing to fire) constant mechanical contact and therefore the least amount of resistance to your rails. I don't really know how to make that much clearer.
Re: railgun
Electroholic, Wed Mar 28 2007, 01:59AM
it doesn't matter how you connect the caps, maximum energy capacity would not change.
You might have too much friction on the rail/projectile contact.
also steel is not ideal rail material, and they are way too long for a 18J cap bank.
with that amount of energy, you can try to seal the end and let the explosion propel the projectile. make it an ETC gun.
Electroholic, Wed Mar 28 2007, 01:59AM
it doesn't matter how you connect the caps, maximum energy capacity would not change.
You might have too much friction on the rail/projectile contact.
also steel is not ideal rail material, and they are way too long for a 18J cap bank.
with that amount of energy, you can try to seal the end and let the explosion propel the projectile. make it an ETC gun.
Re: railgun
dixie43, Wed Mar 28 2007, 02:21AM
What material would you suggest that is better than steel for the rails.
What would you suggest for a projectile. I only need to fire the projectile approximately one to two meters.
[Edit: Fixed double post]
dixie43, Wed Mar 28 2007, 02:21AM
What material would you suggest that is better than steel for the rails.
What would you suggest for a projectile. I only need to fire the projectile approximately one to two meters.
[Edit: Fixed double post]
Re: railgun
..., Wed Mar 28 2007, 02:55AM
For the rails, copper is best.
For the projectile, I have seen aluminum, copper, brass, and graphite used.
For your case, I would recommend changing the topology a little:
1. Seal one end of the gun (preferably the end that the caps are connected to)
2. Make a projectile by taking some plastic (whatever kind will work) and glue a little aluminum to the back.
Muzzle load, and when you fire the aluminum will vaporise, creating a lot of hot gas, launching out the plastic. You will probably also get a small amount of force from the railgun action (actually most big guns use this, it is called a plasma armature)} but you will get a decent amount of the energy you put in into that projectile.
And you can still call it a railgun, powerlabs style!
..., Wed Mar 28 2007, 02:55AM
For the rails, copper is best.
For the projectile, I have seen aluminum, copper, brass, and graphite used.
For your case, I would recommend changing the topology a little:
1. Seal one end of the gun (preferably the end that the caps are connected to)
2. Make a projectile by taking some plastic (whatever kind will work) and glue a little aluminum to the back.
Muzzle load, and when you fire the aluminum will vaporise, creating a lot of hot gas, launching out the plastic. You will probably also get a small amount of force from the railgun action (actually most big guns use this, it is called a plasma armature)} but you will get a decent amount of the energy you put in into that projectile.
And you can still call it a railgun, powerlabs style!
Re: railgun
dixie43, Wed Mar 28 2007, 03:02AM
thanx, for the idea, and anyone else who has an idea to make my railgun more effecient, please add them.
dixie43, Wed Mar 28 2007, 03:02AM
thanx, for the idea, and anyone else who has an idea to make my railgun more effecient, please add them.
Re: railgun
Bjørn, Wed Mar 28 2007, 12:04PM
You need highest possible current and lowest possible friction. If you can't measure the current then you are working blind. If you don't know the ESR of your capacitors then only luck can make you succeed.
To reach your target with such a low energy you need a well made railgun. I suggest that you make an efficient coil-gun first to learn more.
Bjørn, Wed Mar 28 2007, 12:04PM
You need highest possible current and lowest possible friction. If you can't measure the current then you are working blind. If you don't know the ESR of your capacitors then only luck can make you succeed.
To reach your target with such a low energy you need a well made railgun. I suggest that you make an efficient coil-gun first to learn more.
Re: railgun
Wolfram, Wed Mar 28 2007, 01:47PM
If you have five 80µF 60V caps, as you stated in your first post, then you have 0.72J in total. If you had a hundred times this, it might be possible. If you had a thousand times this, it should make a usable small railgun. Unless you can get several hundred of these caps, I'd start looking for some better caps.
Wolfram, Wed Mar 28 2007, 01:47PM
If you have five 80µF 60V caps, as you stated in your first post, then you have 0.72J in total. If you had a hundred times this, it might be possible. If you had a thousand times this, it should make a usable small railgun. Unless you can get several hundred of these caps, I'd start looking for some better caps.
Re: railgun
dixie43, Wed Mar 28 2007, 05:02PM
where would i be able to find really good caps? Would it be more efficient to connect the caps in series or in parallel?
dixie43, Wed Mar 28 2007, 05:02PM
where would i be able to find really good caps? Would it be more efficient to connect the caps in series or in parallel?
Re: railgun
Eric, Wed Mar 28 2007, 06:55PM
Photo flash caps are 'good' in that they have low ESR and are designed for high current output but you should be able to use just about any electrolytics. You ought not to need more than 300V-400V if your circuit resistance and inductance is kept to a minimum. Most people use big filter capacitors from switching power supplies. They are easy to find on ebay.
The big limiting factor with electrolytics and railguns is their high ESR, so generally you'll be better off with caps wired in parallel. Caps should have a voltage rating in the ballpark of 300V-600V.
As others have said, steel rails are very bad. They have high resistivity and also very high AC resistance due to skin effect in comparison to copper. The net effect is that they are ~100 worse than copper and will limit your peak current.
Eric, Wed Mar 28 2007, 06:55PM
Photo flash caps are 'good' in that they have low ESR and are designed for high current output but you should be able to use just about any electrolytics. You ought not to need more than 300V-400V if your circuit resistance and inductance is kept to a minimum. Most people use big filter capacitors from switching power supplies. They are easy to find on ebay.
The big limiting factor with electrolytics and railguns is their high ESR, so generally you'll be better off with caps wired in parallel. Caps should have a voltage rating in the ballpark of 300V-600V.
As others have said, steel rails are very bad. They have high resistivity and also very high AC resistance due to skin effect in comparison to copper. The net effect is that they are ~100 worse than copper and will limit your peak current.
Re: railgun
dixie43, Wed Mar 28 2007, 07:09PM
What can i use instead of copper that is a good conductor?
dixie43, Wed Mar 28 2007, 07:09PM
What can i use instead of copper that is a good conductor?
Re: railgun
Ronnie, Wed Mar 28 2007, 07:57PM
Aluminium is a good alternative if you can't find copper, it is a lot easier to find at an affordable price, but it is still better than steel. Try googling for statistics of different materials - electric conductivity, melting point, etc. The only way to find out how these numbers combine in real life though is to try it out.
Ronnie, Wed Mar 28 2007, 07:57PM
Aluminium is a good alternative if you can't find copper, it is a lot easier to find at an affordable price, but it is still better than steel. Try googling for statistics of different materials - electric conductivity, melting point, etc. The only way to find out how these numbers combine in real life though is to try it out.
Re: railgun
dixie43, Wed Mar 28 2007, 08:08PM
I have aluminum rails i can use instead of steel (15 inches each) and i have found cheap caps that have a voltage rating of 330v and 120uf each. I am using speaker wire to connect my caps to the camera flash board and the rails. How many caps of 330v and 120uf would i need to fire my projectile (small piece of aluminum, until i can find a more effecient projectile) 5-10 feet?
dixie43, Wed Mar 28 2007, 08:08PM
I have aluminum rails i can use instead of steel (15 inches each) and i have found cheap caps that have a voltage rating of 330v and 120uf each. I am using speaker wire to connect my caps to the camera flash board and the rails. How many caps of 330v and 120uf would i need to fire my projectile (small piece of aluminum, until i can find a more effecient projectile) 5-10 feet?
Re: railgun
Ronnie, Wed Mar 28 2007, 08:21PM
It would be impossible to predict that due to the number of different factors that would need to be considered. Use the fattest cable you can obtain, and perhaps 30 photoflash capacitors. If range is all that matters, use a slightly smaller piece of aluminium foil. As it weighs less it will be go faster, within reason. Try all different shapes, sizes and materials for the projectile, be creative :)
Ronnie, Wed Mar 28 2007, 08:21PM
It would be impossible to predict that due to the number of different factors that would need to be considered. Use the fattest cable you can obtain, and perhaps 30 photoflash capacitors. If range is all that matters, use a slightly smaller piece of aluminium foil. As it weighs less it will be go faster, within reason. Try all different shapes, sizes and materials for the projectile, be creative :)
Re: railgun
dixie43, Wed Mar 28 2007, 09:29PM
How long should my aluminum rails be, to shoot 5 to 10 feet and not waste any energy on extra resistance from rails that are too long.
dixie43, Wed Mar 28 2007, 09:29PM
How long should my aluminum rails be, to shoot 5 to 10 feet and not waste any energy on extra resistance from rails that are too long.
Re: railgun
Ronnie, Wed Mar 28 2007, 10:42PM
For lower energy levels, you can use silicon controlled rectifiers to switch power, search the forums and you'll find a few topics about them, and other ways you can improve efficiency, also make sure that your setup is safe - especially protect yourself from unexpected shrapnel from the circuitry, check the voltage on the capacitor bank before touching anything, etc, you can never be too careful.
Ronnie, Wed Mar 28 2007, 10:42PM
For lower energy levels, you can use silicon controlled rectifiers to switch power, search the forums and you'll find a few topics about them, and other ways you can improve efficiency, also make sure that your setup is safe - especially protect yourself from unexpected shrapnel from the circuitry, check the voltage on the capacitor bank before touching anything, etc, you can never be too careful.
Re: railgun
dixie43, Wed Mar 28 2007, 11:20PM
Would it be a good idea to connect the caps in series to increase the voltage, which would lower the amound of energy loss and then use a step-down transformer to lower the voltage and increase the current going through the rails?
dixie43, Wed Mar 28 2007, 11:20PM
Would it be a good idea to connect the caps in series to increase the voltage, which would lower the amound of energy loss and then use a step-down transformer to lower the voltage and increase the current going through the rails?
Re: railgun
Electroholic, Thu Mar 29 2007, 01:45AM
i think you got some googling to do before starting a project like this and/or starting a thread.
problem with alu rails is that they have too low a melting point and welds all the time. especially with your small capacitor bank.
rails for my 1kJ gun is 200mm long, 4mm*4mm bore.
OFC rails, and shoot a specially designed projectile.
Electroholic, Thu Mar 29 2007, 01:45AM
i think you got some googling to do before starting a project like this and/or starting a thread.
problem with alu rails is that they have too low a melting point and welds all the time. especially with your small capacitor bank.
rails for my 1kJ gun is 200mm long, 4mm*4mm bore.
OFC rails, and shoot a specially designed projectile.
Re: railgun
dixie43, Fri Mar 30 2007, 12:36AM
I have very limited resources, and can only get capacitance around 300v at 2400uf, is it still possible to fire a small projectile off, 10in Aluminum rails with a good connections to the rails?
dixie43, Fri Mar 30 2007, 12:36AM
I have very limited resources, and can only get capacitance around 300v at 2400uf, is it still possible to fire a small projectile off, 10in Aluminum rails with a good connections to the rails?
Re: railgun
Electroholic, Fri Mar 30 2007, 03:39AM
2400uF at 300V is a hundred J, I hope you know what you are doing. expect long charge time if you are planning on using camera flash circuits.
as i said, Alu is bad as it has very high friction, especially Alu on Alu. Low melting point is also a problem, welds easily.
Copper is ideal, brass works too.
if you have a lot of time and are good with tools, you should be able to get two strips of brass out of a standard brass door hinge. grind it true and you will have a set of rails.
rails don't need to be long. unless, you want to cheat a bit and make a ETC gun that runs on alu foil.
just like ... said, make sure your barrel is air tight, and sealed at one end.
then its just pressure and F = ma.
Electroholic, Fri Mar 30 2007, 03:39AM
2400uF at 300V is a hundred J, I hope you know what you are doing. expect long charge time if you are planning on using camera flash circuits.
as i said, Alu is bad as it has very high friction, especially Alu on Alu. Low melting point is also a problem, welds easily.
Copper is ideal, brass works too.
if you have a lot of time and are good with tools, you should be able to get two strips of brass out of a standard brass door hinge. grind it true and you will have a set of rails.
rails don't need to be long. unless, you want to cheat a bit and make a ETC gun that runs on alu foil.
just like ... said, make sure your barrel is air tight, and sealed at one end.
then its just pressure and F = ma.
Re: railgun
dixie43, Fri Mar 30 2007, 11:24AM
So far, i have only been able to find flash circuits in a camera to charge up my capacitance but, thanks for info about using brass as rails, if i can't make it work than i will seal one end and use a plasma armature.
dixie43, Fri Mar 30 2007, 11:24AM
So far, i have only been able to find flash circuits in a camera to charge up my capacitance but, thanks for info about using brass as rails, if i can't make it work than i will seal one end and use a plasma armature.
Re: railgun
uzzors2k, Fri Mar 30 2007, 07:07PM
I recommend that you start with a coil gun, as this is obviously your first project. You can use all the materials you already have + some wire for the coil. Have you seen those photo-flash coil guns, there are hundreds of them on google and you are almost guaranteed a result. Use the various calculators at the magnetic gun club and you should be able to make a coil gun which can shoot at least 10 feet. Once you get that down, then work on a rail gun.
uzzors2k, Fri Mar 30 2007, 07:07PM
I recommend that you start with a coil gun, as this is obviously your first project. You can use all the materials you already have + some wire for the coil. Have you seen those photo-flash coil guns, there are hundreds of them on google and you are almost guaranteed a result. Use the various calculators at the magnetic gun club and you should be able to make a coil gun which can shoot at least 10 feet. Once you get that down, then work on a rail gun.
Re: railgun
dixie43, Fri Mar 30 2007, 09:41PM
I can't build a coilgun for this project but, can anyone give me an idea of an easy to build electromagnetic projectile accelerator so i can research it, and try to build it before attempting the railgun.
dixie43, Fri Mar 30 2007, 09:41PM
I can't build a coilgun for this project but, can anyone give me an idea of an easy to build electromagnetic projectile accelerator so i can research it, and try to build it before attempting the railgun.
Re: railgun
ap, Sat Mar 31 2007, 02:54AM
disc launcher?
ap, Sat Mar 31 2007, 02:54AM
disc launcher?
Re: railgun
dixie43, Sat Mar 31 2007, 03:35AM
Ok, ill check it out, thanx. any other beginner projects on EM projectile accelerators would be appreciated as well.
dixie43, Sat Mar 31 2007, 03:35AM
Ok, ill check it out, thanx. any other beginner projects on EM projectile accelerators would be appreciated as well.
Re: railgun
uzzors2k, Mon Apr 02 2007, 05:49PM
The Micro-railgun is small, cheap, and simple, maybe you will have better luck with it. Otherwise a coil gun is the most simple.
uzzors2k, Mon Apr 02 2007, 05:49PM
The Micro-railgun is small, cheap, and simple, maybe you will have better luck with it. Otherwise a coil gun is the most simple.
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