How to make a RAILGUN!

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

Comments

[evandereems]

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]

Yeah im the friend... no idea... maybe we need to charge up the rails then put the projectile on?

[jj.inc]

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]

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.

[jj.inc]

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]

Yeah, thats just wrong. Joules are a unit of energy. Horsepower is a measure of power.

[jj.inc]

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.

[swagner4]

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

[jj.inc]

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]

Wow i cant believe i fell for a troll. Kudos

[jj.inc]

BTW that wasn't off-topic, and I am not a troll.

[swagner4]

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.

[jj.inc]

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]

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]

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.

[jacobwallace]

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".

[ThoranAdvancements]

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]

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]

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]

increasing the length of your rails may help.F=LxIxB F=force L= length of the rails I=current B= magnetic field

[lasermaster3531]

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.

[nadams-2]

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]

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]

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]

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]

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]

try an extremely small sliver of foil (pinhead size) and a very large cap bank.

[nickbowlingdude]

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]

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]

compressed gas would probably be the safest and easiest i would suggest using either oxygen or co2.

[munitionsgeek]

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]

O2 would be bad because with the sparks produced it could potentially ignite

[ItsTheFark]

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]

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]

Will the ferromagnetic projectile accelerate uniformly along the two rails?

[thestyrofoampeanut]

if it works its supposed to

[Arduino Guy]

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]

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]

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]

make this, it works great. http://www.instructables.com/id/DC-DC-HV-Boost-Converter/