# How to make a RAILGUN!

6 Steps

## Step 6: Fire!

press the small button to charge up the capacitor bank
when the led blinks you can press the big button and fire it
after you're done use a srewdriver to trigger the capacitors a few times before touching it
Remove these ads by Signing Up
jj.inc says: Mar 8, 2011. 8:37 PM
So you don't need anything to jump start you projectile, I know larger ones use compressed air or springs to avoid welding the projectile to the rails. Also does yours throw cool sparks and stuff, maybe even plasma?
cex in reply to jj.incOct 5, 2011. 6:05 PM
uhm... Yeah, for a railgun to have enough force to create plasma, it would need several megajoules of energy (if you saw the railgun from DARPA or the US Navy, that one shot took so much energy that it could've been used to power a city for a year).

To release sparks, a railgun doesn't have to be THAT powerful, but it still requires a fairly large amount of energy. In short, THIS railgun can't be used to kill people or do any heavy damage.
not really.
this one throws plasma with a kilojoule.
jj.inc in reply to cexOct 5, 2011. 6:44 PM
the biggest railgun (navy) was 33 megajoules or 30000000 joules, or a little over 12 horsepower, I see what you mean, but using a 12 hp engine to charge batteries for one hour couldn't power my house for a year.
swagner4 in reply to jj.incOct 9, 2011. 10:58 PM
Yeah, thats just wrong. Joules are a unit of energy. Horsepower is a measure of power.
jj.inc in reply to swagner4Oct 10, 2011. 5:56 AM
but power over time is energy right.
I just found all of this information,
Watt x Time = Joules This is 8948 time 3600 secconds = 32,212,800 joules which is a pretty good conversion for the one minute I put in.
Power x Time = Work (energy)

Joules/distance = Newtons
Work/distance = Force

So you can convert power to energy, its just a little more complicated than most conversions.
malleolus in reply to jj.incAug 25, 2012. 4:54 AM
The joules are calculated as
(voltage^2*capacitance)/time=joules when you are referring to a railgun. Joules of energy is what is important rather than the work for a railgun. And the proper conversion for figuring the force delivered by the projectile is actually mass times acceleration. Astoundingly this works out in the physical world because, like in a rifle, once the projectile leaves the force acting upon it, in this case the magnetic field is the accelerating force, the projectile is immediately in deceleration unless it is shot along a parabolic path, in which case it could possible experience some acceleration once it passes its apex due to acceleration induced by gravity IF it has decelerated below it's terminal velocity.

And horsepower is how long it takes a team of horses (later revised to a force) to drag a 200lb object over a given distance, so it literally has no application in a railgun. Google is NOT reliable for conversions.
swagner4 in reply to jj.incOct 11, 2011. 4:34 PM
Look, you cant just assume time. And the first guy was wrong as a city uses about 2 Gigawatts each year.

But charging and equations are not linear which you are assuming. By your logic you can convert Joules into cubic meters
crob09 in reply to swagner4Aug 2, 2012. 7:19 PM
You can,

Joules/Newtons = Distance
Work/distance = Force

All you need is an Axiom, math does not lie, equations are linear; What isn't linear would be how the rules are applied.

Newtons third law: For every action there is an equal and opposite reaction

Einsteins theory of relativity: energy cannot be destroyed or created only transfomed
jj.inc in reply to swagner4Oct 12, 2011. 6:18 AM
I did it, I converted joules to liters of gasoline, one cubic meter equals 1000l so yea I will do that too. So because one liter of gasoline contains about 35 MJ I will just say that we have 35 MJ. That is equivalent too 0.001 cubic meters, hooray. I hate ruining peoples day.
swagner4 in reply to jj.incOct 12, 2011. 11:25 AM
Wow i cant believe i fell for a troll. Kudos
jj.inc in reply to swagner4Oct 12, 2011. 5:09 PM
BTW that wasn't off-topic, and I am not a troll.
swagner4 in reply to jj.incOct 12, 2011. 9:19 PM
Look, I'm a double major in physics and chemical engineering and I am telling you that while I understand why you are thinking what your thinking, it is incorrect.

You are not converting. You are doing calculations. A conversion changes things that are equivalent. You can only change Joules into other energy units.

Further, you are ignoring inefficency, heat transfer, momentum and impulse, how magnetic fields work, charging and discharging of capacitors and other things.

Also, the electricity that is used is in watt hours when calculated.

That is what is what is wrong with what you are doing.
crob09 in reply to swagner4Aug 2, 2012. 12:57 PM
1 watt is equal to 1 joule, "jj.inc" is correct.

All you need is an Axiom and you can convert anything you like.

For example:
Under this situation the Axiom is a Joule, and we know that 1 joule = 1 watt. We also know that Wattage is PxA.
So I can have a power supply rated at 2V .5A that = 1Watt or a supply with a power rating of .5V and 2A = 1Watt.

I think our education system is in trouble when a person with a Physics and Mechanical engineering degree thinks that Power and Energy are different.
Maybe "jj.inc" is wrong about other things but he isn't wrong about that.

Einsteins theory or relativity: Energy cannot be created nor destroyed only transformed.

Don't tell me you beleive in overunity?
jj.inc in reply to swagner4Jun 15, 2012. 10:34 PM
Heyo, I was just looking through and I figure I would see if you had my final results yet Mr. Braniac. If you realized I was right you should at least admit it, and if you know what I did wrong please explain so the world can become a better place. After glancing through my very first comment I see what you caught me on, but I subtley place the time into the factor in the last half of my comment. Just ignore this: "he biggest railgun (navy) was 33 megajoules or 30000000 joules, or a little over 12 horsepower" and read this: but using a 12 hp engine to charge batteries for ONE HOUR couldn't power my house for a year.
jj.inc in reply to swagner4Oct 13, 2011. 6:03 AM
You could have just told me I was using the wrong word to explain what I was doing. Its really not that big of a deal. Yea, I did ignore all of that intentionally to say that in absolute best conditions with no energy loss, it still only provided a certain amount of energy. I don't see where I messed up this whole watt hours thing either. I provided time for every "calculation" I did, it doesn't have to be watt hours. I had 33 MJ I calculated that out to watts over a period of time. That is all I did, and that is all I needed to do. Do you understand this?
jj.inc in reply to swagner4Oct 12, 2011. 5:08 PM
I am sorry, I just don't like it when someone says no your wrong, I just don't have any real numbers or facts to back it up so I will just muble around and insult you.
jj.inc in reply to swagner4Oct 11, 2011. 7:38 PM
No, I am saying 33 gigajoules is equivalent to 12hp over 1hour. Which it is. I just converted the hp to watts, which is perfectly fine, then I plugged in the proper time which is in secconds, one hour = 3600 secconds. 12hp is very roughly rounded, and the concluded answer was extremely comparable. If I directly converted 12hp over to electrical watts with no loss of energy I would still only get roughly 9kw which would be enough energy if stored to run my house which consumes 3kwh for roughly 3 hours. Its a bunch of math, but it is well reasoned. I know it is difficult to understand converting between these to things.

Joules are a measure of energy (energy is defined as the ability to do work)
Work is power * time and is measured as an SI unit of joules
Power is the rate at which work is performed or energy is converted
Time is, well you know what time is

By looking closely at these properties you can conclude that power over time is work or hp over one hour is joules

When I use the word over I don't refer to a fraction or division problem I refer to something occurring over a period of time.
06sandj in reply to jj.incJun 14, 2012. 10:04 AM
The problem with this calculation is that the railgun mentioned discharged its energy over a fraction of a second. Your calculation provides a power of around 9000W: in reality, it would be more like 3300000000W (almost 4.5million horsepower), based on a guesstimation of a 0.01s discharge time.
crob09 in reply to 06sandjAug 2, 2012. 3:13 PM
Wrong.
The energy is being stored then released, hence the capacitors. There is always some energy loss but not that much.

Think of your car engine, the energy loss is caused from heat, vibration, friction, noise, just to name a few things, all can be measured and combined they total the energy used to run it.
Hydrogen has an exothermic reaction of about 286000 joules per mol, that means the energy released when hydrogen combines with Oxygen is 286,000 Watts, gas is probably pretty close to that too, but you don't see that power at your wheels.

In this situation we have less energy loss, no vibration or noise until you release the energy stored.

Robert Goddard: "For every action there is an opposit and equal reaction"
jj.inc in reply to 06sandjJun 15, 2012. 10:30 PM
Oh, dude, I am so sorry. I have no idea where giga came from, it should have been mega the whole way through, which would drastically bring down your power rating. Sorry I failed as bad as you.

-Face Palm-
jj.inc in reply to 06sandjJun 15, 2012. 10:22 PM
Could you please explain more thoroughly. Time plays no role in these calculations. If something is 33 gigajoules, it is 33 gigajoules for a second, and 33 gigajoules for a day. It is just 33 gigajoules.

Ha ha, I was just doing some math and you are just a failure. 33 gigajoules is 3,000,000,000 joules. That number is one 0 short of your number (typo probably). Also sure you may get 4.5 million hp (DON'T QUOTE ME I AM USING YOUR DATA AND IT IS TOO LATE AT NIGHT FOR ME TO CHECK IT), but you only get 4.5 million hp for 0.01 seconds. If you calculate that out which I can't think of how to do at this time you will only have a few horsepower over the course of a short time.

-to everyone other than 06sandj Please disregard this post as the information is useless and just a poorly compile explanation of the massive fail seen above.
malleolus in reply to jj.incAug 25, 2012. 4:19 AM
When you are talking work done by electricity being converted into a working medium, like the magnetic field, strength is a product of it being divided by time. So 1 hour of charging with a 12hp motor will not equate into the aforementioned joules of force. This is why it does NOT require an entire nuclear power facility to reach the fire rate that the weaponized version is projected to reach. You have to take a fairly strong power source, like a compulsator or bank of capacitors, and discharge the stored energy at an extremely rapid pace, far faster than a hundredth of a second. This is why it's so hard, pulsed power sources able to reach the required pulse lengths are extremely crude, inefficient, and bulky. YES, you can make it work on paper, but that's not how it turns out in reality.
06sandj in reply to jj.incJun 16, 2012. 7:42 AM
Yes, the energy is the same, no matter the amount of time; however, you were quoting power, which does include time. The 4.5million hp came from google calculator (3300000000 watts in horsepower) - I'm not exactly a units conversion wizard myself :P I get your point, and it's true what you're saying about powering a city for a year - I was just attempting to point out that you were referring to the power of this particular railgun as 12hp. This may have just been unclear writing or me not understanding your comment particularly well. On the whole, we should probably forget all about this conversation, agree that railguns are pretty awesome, and continue with life :)
jj.inc in reply to 06sandjJun 16, 2012. 8:08 AM
oh, no, I wasn't saying the railgun had 12 hp, but the idea that it produces 4.5 million for 0.01 seconds is kinda cool
06sandj in reply to jj.incJun 16, 2012. 9:07 AM
All cleared up then :) And yes, it is :P Imagine the recoil on that thing - slight problem to firing it from a ship!
ok im not very experienced with this subject, but to my understanding recoil is caused by the expanding gasses from the explosion of gunpowder (or whatever other explosive propelent you could use). so as long as you only used magnetic fields to eccelerate your projectile, and made shure to ventilate the rails, or barrel used to house your projectile, the only recoil you should experience should only be (not shure exactly how to say this, but hopefully this will work) the guns movement related to the inertia of the projectile which would keep it resting. if any of that is wrong plaese correct me.
Every action has an equal but opposite reaction (one of them newton laws). When the magnetic field pushes the projectile the projectile pushes back just as hard. Now on a small railgun you won't notice it because the projectiles are usually very small and not going very fast, but the navy gun shoots a very heavy projectile at extreme unimaginable speed, this results in a huge amount of opposite force.
yeah i know about newtons third law but (and again im not very experienced with this) wouldent the force of the "opppsite force" be distributed more or less evenly into the gun (kinda like if a baseball hits a barrel of water, the barrel doesent go flying at the same speed the baseball was traveling) so if a railgun which accelerates a 40 lb projectile to 5,500 mph, which i roughly calculated to require about 54.5 million joules (or 1.36 million joules per pound), was mounted in a platform weighing 5,000 pounds it would only have a recoil of around 272 joules (around twice the recoil of a barret .50) which i think a 16 million pound ship could easily take. now im shure i made some mistake somewere in there so please correct me
I'm not to great with the numbers either, but I think you are probably right, it shouldn't do too much to move the ship, but it would still be 5000 pounds pushing back at 272 joules, which I am sure you would feel. Being anywhere near the thing could be really dangerous I imagine. I wounder what the electromagnetic field around it looks like.
yeah the biggest problem i could imagine is the cannon going off and taking anything magnetic that isnt tied down (and possibly part of the ship) with it. lol i can see the headlines now "navy sends railgun superweapon into battle, oblitorates enemy ship...and sinks own ship in the process"
agreed.
seeing where they got the energy and how big the power source is would also be funny.
evandereems says: Nov 27, 2011. 3:20 PM
So my friend and i made something a lot like this, but when we discharge the capacitors on the rails, the projectile just jumps a little. What could be the problem?
jmorey3 in reply to evandereemsNov 28, 2011. 11:52 AM
Yeah im the friend... no idea... maybe we need to charge up the rails then put the projectile on?
jacobwallace says: Mar 10, 2011. 12:52 PM
I apologize in advance for the long thread. But, i stumbled across this project and by the looks of it there needs to be further explanation to those who want to build there own Rail gun. First off this is not a rail gun. A true rail gun uses 4 sided rails for its propulsion. This gun only uses two. Second the problem with using iron or aluminum for the rails poses many problems. One of which is the field strength of an electromagnet is determined by one of two things. The type of ferromagnetic conductor and the voltage applied upon that conductor. So, when you build a capacitor bank you are in essence delivering a charge so high that the iron or aluminum rods cannot effectively deliver propulsion but, instead they use the same Lorentz force for projection to vaporize the ferromagnetic material between the two rails. The charge delivered from the capacitors is simply to high for a common piece of iron or copper or aluminum to handle. Instead of firing it the intense magnetic field powered by the immense current running through the rods will become a fantastic welding kit. If you want to build a rail gun you must either double the rails by adding two more which should sufficiently decrease the charge enough to fire an object or you must lower the voltage output delivered onto the conducting rods. this means using 1 fewer capacitor. Or you can keep everything the same and buy a can of polyethylene urtex coating. Which when sprayed on to the iron or aluminum rails should prevent most of the heat transfer that bonds your projectile to begin with. But increasing the number of rods, lengthen the rods or even lowering the voltage output is the only way to successfully fix this quote on quote "welding to the rails dilemma".
So what type of material would you suggest i use for a Railgun? Ive been thinking about doing this project for a while now, but i cant seem to understand the steps of the process to build a Railgun.
Synn says: Aug 8, 2009. 3:36 PM
I'll appologise in advance about the length of this :P i'm new to the site and i've made this my first(ish) project. (i made a camera taser with a few mods to it). I've followed your plans exactly and anything i try firing out of my gun just sparks and weld's to the steel rails, have i missed something out or done something wrong? I have a lot of copper i can use for rails, would this help any, because i know copper conducts better than steel. Allso, my capacitor bank (made from a few camera's, TV, Satellite Box and an Amp) charges well as it is from the camera circuitry, if i add a second circuit to this, will it charge at a quicker rate, or damage the capacitor's? Last question, i allso heard someone mention an "armiture"? i think it was called, so i can fire non conductive materials, how does this work? Sorry for the long comment, i wanted to get everything in this one :P I look forward to any help you guys could give me
techno_pig in reply to SynnFeb 18, 2011. 5:07 AM
You don't need anything magnetic. Any material with a current passing through it has a magnetic field that is perpendicular to the current. I think your problem maybe can be solved by using slightly smaller projectiles, made from something a little tougher than you've been using. Even if your projectile welds a little bit, the Lorentz forces should overcome the stick from the weld. You either need smaller projectiles or more current.
matthewtyler1 in reply to SynnJan 23, 2011. 7:32 PM
increasing the length of your rails may help.F=LxIxB F=force L= length of the rails I=current B= magnetic field
lasermaster3531 in reply to SynnSep 23, 2010. 5:18 PM
this railgun is not designed to fire anything bigger than a grain of sand. it uses the arcing to vaporize the aluminum bit and push the superheated plasma out of the barrel, but it just isn't big enough for anything solid.
well crap i went to build one of these rail guns and i was trying to figure out why it wont make my object go which is very small. do u have any suggestions one what i would need to make an object actually go off the rails
Marshal Banana in reply to SynnAug 8, 2010. 8:04 AM
I don't know about an armature, but you could try to make a sabot. It is what tanks use to fire their depleted Uranium rounds. Here is a link. http://en.wikipedia.org/wiki/Sabot
Gixtox in reply to SynnJan 24, 2010. 8:31 PM
1. no prob about the length.
2.Ok so what I'm guessing the welding is because of how much power you are shooting through the projectile at once. My recommendation, use an armature.
3. Ok so what an armature is, is basically a holder for anything that isn't magnetic. It holds whatever you want to fire. The armature itself is magnetic so when the armature flies down the rails it takes the new projectile with it. Don't ask how to make one i have no idea.
thestyrofoampeanut in reply to SynnAug 12, 2009. 9:10 PM
this is my first project too its not my vid but i think i can help you a bit For a projectile try using something mainly composed of iron, cobalt, or nickel I dont know what you exactly what you used for your capacitor bank, but i would stick to just adding camera capacitors to one more camera capacitor(btw try making a big bunch of capacitors in parallel instead of stacking them like he did) don't know about the "second circuit" question never heard of an armiture hope i helped
sausabe says: May 1, 2007. 10:39 PM
How exactly did you get this johnny to fire. I'm having severe problems there (and your instructions are a bit vague.) I did deviate from your instructions a bit, but if you (or anyone) could give me any insight, that'd be just spiffy. I've got a current, and a complete circuit, but whatever I try to shoot just ends up twitching or welding itself to my rails.
lasermaster3531 in reply to sausabeSep 23, 2010. 5:12 PM
try an extremely small sliver of foil (pinhead size) and a very large cap bank.
nickbowlingdude in reply to sausabeMay 13, 2008. 6:06 PM
To have an effective railgun, you need some means of starting the projectile in motion before the lorentz forces can take over. Compressed air works nicely, or maybe gunpowder if you want to take the risk.
CyclonicNinja in reply to nickbowlingdudeApr 25, 2011. 8:36 AM
you could add something like a coilgun behind it so the coilgun propels the projectile forwards than it enters the railgun and then accelerated further.
Could that work?

something a bit like this (sorry uploader doesn't work):

http://www.instructables.com/file/FDOXI28GMX1XROI/

Keith
general-Insano in reply to nickbowlingdudeJan 30, 2009. 9:27 PM
compressed gas would probably be the safest and easiest i would suggest using either oxygen or co2.
munitionsgeek in reply to general-InsanoJan 17, 2011. 8:02 PM
safest would probly be to run another set of wires to a separate magnetic rail placed behind the projectile to give it the initial "push"
manoaguy in reply to general-InsanoSep 3, 2010. 10:59 PM
O2 would be bad because with the sparks produced it could potentially ignite
ItsTheFark says: May 30, 2009. 3:30 PM
OK so i just finished making my Rail Gun, almost the exact same specs as the one AlexTheGreat demonstrates, except my rails are larger. The space between the rails is 1.6mm and im using that sized aluminum wads. When i fire it it just sparks and the aluminum wad stays stationary. I read the posts below this and it is all based on the aluminum welding itself to the rail, but that is not happening... the aluminum is just not moving. Help!
xarlock667 in reply to ItsTheFarkMar 11, 2010. 8:16 PM
Your aluminum is probably "Bouncing" and the electricity is arcing under it. Have you tried placing an inert rail over it, and injecting the projectile from the rear?
JKai says: May 27, 2008. 4:07 AM
Will the ferromagnetic projectile accelerate uniformly along the two rails?
thestyrofoampeanut in reply to JKaiAug 13, 2009. 8:29 PM
if it works its supposed to
Arduino Guy in reply to thestyrofoampeanutDec 6, 2009. 4:38 AM
Actually Railguns do not propel ferromagnetic projectiles the projectile has to be Diamagnetic such as materials like Aluminum, Copper and Carbon.(Carbon is not Graphite.)
xarlock667 in reply to Arduino GuyMar 11, 2010. 7:58 PM
Railguns do not require that the projectile do anything but be solid, and conduct electricity.Ferrous/nonferrous simply does not matter. It is actually repelling the electric field, not the projectile. Kind of like a Jacob's ladder, but faster. The projectile is just along for the ride.

In case anyone in interested, the force equation for a rail gun is F=BILD/M^2, where the Force generated is equal to the magnetic field B times the current in ampres I times the length of the barrel L times the distance between the rails D divided by the mass of the projectile squared M. A lot of anoying math.
anthonyremo says: Oct 7, 2009. 6:40 PM
Is there a way to make this rail gun without using the camera citcuit board??? bsaically can you charge up the capacitors directly from a power source?
jeremy_smith in reply to anthonyremoNov 14, 2009. 8:49 AM
make this, it works great. http://www.instructables.com/id/DC-DC-HV-Boost-Converter/
TheDoci in reply to anthonyremoOct 16, 2009. 11:33 AM
yes you can if you have 330V!

hg341 in reply to anthonyremoOct 10, 2009. 9:03 PM
yes you can but you would need to have a 330v ps. that would be 220 AA'S in series so over all it saves a lot of time to use the camera citcuit
kurisu2 in reply to hg341Nov 29, 2009. 1:20 AM
Actually 300 volts. The capacitors are rated for 330 because it is generally a good idea to use capacitors that can hadle 10% higher voltage than what the device is intended for so they do not fail.
hg341 in reply to kurisu2Nov 29, 2009. 8:32 AM
na i dont care if they blow they where free and i keep them covered at all times
cclark13 says: Jun 26, 2009. 9:01 PM
you need to make a video
kevin_barbian says: Jun 12, 2009. 12:37 AM
I thought that you need to have non-magnet reactive projectile but conductive? for rail gun but coil gun needs (damm brain fart) ferric? (things magnet will stick to) hope I didn't let my ignorance out
jim617 in reply to kevin_barbianJun 16, 2009. 11:22 PM
aluminum slugs
bodo says: Apr 7, 2009. 4:02 AM
just use something betveen the rails and projectile sach as anoder metal that does not melt quick ore try to regulate the current lower
Mattrox says: Apr 11, 2008. 11:06 PM
er what stops it shooting out the back
not-killerk in reply to MattroxNov 16, 2008. 7:09 PM
the forward lorentz force, it will always force the projectile in the direction of the current.
Actually the force is perpendicular to the current. If it were parallel to the current then the projectile would just push itself into one of the rails
Mattrox in reply to not-killerkNov 17, 2008. 6:49 PM
thanks brainy dude no sarcasim
not-killerk in reply to MattroxNov 17, 2008. 7:08 PM
no probs, i get it alot lmao. no sarcasm xD
Mattrox in reply to not-killerkNov 17, 2008. 7:18 PM
no seriously no sarcasm
not-killerk in reply to MattroxNov 18, 2008. 3:13 PM
lol. i know. im just saying it cuz u said it , thats all lmao.
montmorency in reply to MattroxNov 13, 2008. 4:34 PM
lol, that wouldn't be too good
miols says: Apr 2, 2008. 5:11 PM
what's it shoot...
emuman4evr in reply to miolsApr 2, 2008. 6:44 PM
Plasma, it fires a ferromagnetice projectile (in this case a wad of aluminum foil) and if theres enough electricity the projectile can turn into plasma and you see it shoot a jet of sparks.
junits15 in reply to emuman4evrJan 22, 2009. 3:06 PM
peices or iron nails work better because they dont vaporize when shot
dylandance in reply to emuman4evrJan 21, 2009. 1:19 PM
haha i doubt the tin foil becomes plasma. he's messing with you miols
Wesley666 in reply to dylandanceFeb 20, 2009. 5:12 PM
if you shoot tin foil out of a 600 amp rail gun, it will be plasma. But on something this small very little would turn into plasma. If you go on youtube and look up rail guns (homemade ones as the military ones have blast guards for this) they have a large flair out the front when shoot and that is the rails and projectile (only a thin layer) turning into plasma. These guns run off of very high amperage. This website is a university students experiment if I am correct and runs at 40000 Amps, and near the bottom of the page are pictures of it firing with the plasma muzzle burst, check it out:

http://www.powerlabs.org/railgun.htm
eggman in reply to dylandanceJan 30, 2009. 7:58 PM
no, it really does become plasma lol.
geeklord in reply to emuman4evrSep 28, 2008. 4:31 PM
O.....K....., I didn't know there was such a thing as a high velocity plasma shooting gun.....(beyond a flamethrower)
action hero says: May 27, 2008. 12:04 PM
looks pretty good , how powerful and accurate is it