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[zchris13]

For the summer, I am looking into having very large quantities of, shall we say, FUN.  In the most grand manner possible.  In the quest of this grand objective, I have settled on a project for my friends and I to work on.  It will be grand, amazing, stupendous, and horrifyingly stupid.

I need a little bit of help: I don't know what I'm doing.  I'm currently looking up the current specs for electricity discharge of several different things, but I don't really know what sort of intermediate power source to use.  I think my options are capacitors and flywheels.  Most likely capacitors, because flywheels have a tendency to explode in your face when you mess with them.  Because they spin really, really, fast.  And a good one is expensive.

I have decided on some dimensions: I need it to be a good size, a little over a meter (SI for convenience, all the electricity equations are readily available in SI units), but that is all I really know.  I do have a nifty equation, telling me the repelling force between the rails as a function of their length and the distance between them, and the current flowing through, but not much else.  I can estimate the speed of the projectile when it leaves the barrel, if I know the force on the projectile.  That's easy.  Harder is knowing just how fast I want this baby to fire, and how hard I'm going to have to work to keep it operational.

Just for clarification, this project is the shit.  Officially.

Does any forumgoer have any experience in this field? Mayhaps experience with electric motors, or anything?

[SHAD0Wdump]

I have but one suggestion: Point away from face...   That is all.

[alway]

I have another suggestion: don't stand anywhere near it. Especially in front or behind.

Remember: for every action, there is an equal and opposite reaction. Or to be more specific, those rails will be shot backward with as much force as the projectile will be shot forward.

From what I've read about railguns, the biggest problems are getting rails durable enough to withstand both the force of the weapon firing and the various effects of the high voltage and various ionized gasses which will form around them. IIRC, the rails will often corrode very quickly due to the ionized gas created by the firing. Corroded rails means no electrical contact, and no more firing. The high temperatures created may also cause the rails to warp. So be sure the rails are either extremely expensive and so won't be affected by the firing for hundreds of shots, or so cheap you can afford to replace them every other shot.

[zchris13]

Force equations for the projectile as a function of magnetic field strength and current?

And yeah, both of you.  I'm not dumb.  I get all that, old news.
You can give me safety tips once I've built the damn thing.

[Aqizzar]

Let me see if I understand what you're saying.  You're going to build a magnetic rail launching system of some kind.  Right?  Yeah, building a maglev line in your backyard isn't exactly what I'd call a "summer project".  I'd have to think you'll need some extremely precise relays and so forth, like computer operated.  I would look into real railgun projects that people with money have done.

[zchris13]

Yo, Aqizzar? Do you know how railguns work?  You run a metric shitton of current up a rail, across a projectile, and down a rail.  The current flowing through the rails makes a magnetic field around the rails (especially between them) and the current flowing across this magnetic field (through the projectile) causes force to happen on the projectile.  And yes, my friend (who is stupid rich) and me (who is sort of kind of rich) will be dumping HUGE amounts of money into this.

I promise to put a video on youtube when I shoot a watermelon with it.

Things you need:

• Electricity
• Something to store the electricity (capacitors, etc. Needs to be able to discharge really quickly)
• Switches
• rails (pricey?)
• a mounting

[Boksi]

The local government will want to know about this. I'm pretty sure not even the deep south US allows citizens to own modern artillery.

But then again, this idea is just crazy enough to actually work. But you might want to contact people at nearby universities et al.

[alway]

Let me see if I understand what you're saying.  You're going to build a magnetic rail launching system of some kind.  Right?  Yeah, building a maglev line in your backyard isn't exactly what I'd call a "summer project".  I'd have to think you'll need some extremely precise relays and so forth, like computer operated.  I would look into real railgun projects that people with money have done.

Actually, railguns operate based on a magnetic field flowing from top to bottom (or vise-versa), a current flowing through the rails and projectile, and the force created by said electric current. The force created is perpendicular to both the field and the current direction (across the projectile). The basic concept is relatively simple, and can be done in a very low speed tabletop variety with just a battery, some wires, a pair of metal rods, and a round metal bar capable of rolling.

Edit: This may be useful: http://en.wikipedia.org/wiki/Railgun#Considerations_in_railgun_design

[ChairmanPoo]

you might want to check this:

http://www.youtube.com/watch?v=kMUErwcuBf8

[Vector]

... I kind of doubt that there will be a government/whatever problem, given that my high school's robotics team/physics classes built one for the hell of it (we're in California, and yes, it was tested on government property).  Unfortunately, I have no idea how they did it--just that they built one, and it worked, and it ate a pretty big chunk out of one of the school's concrete pillars.

The robot that ate cement, though, was far more destructive.

[zchris13]

This is super useful, why did I not see this before.

[Duke 2.0]

 I really don't think an amateur in his backyard will make anything terribly powerful. The whole magnetic rails dissolving things only applies to massive powerful railguns that fire at several times the speed of sound. This will likely be a low-power coilgun that fires metal pellets fast enough to penetrate three inches of wood at best.

[ChairmanPoo]

Don't be too proud of this technological terror you've constructed want to build. The ability to destroy a planet shoot pellets moderatedly fast is insignificant next to the power of the Force

[zchris13]

I really don't think an amateur in his backyard will make anything terribly powerful. The whole magnetic rails dissolving things only applies to massive powerful railguns that fire at several times the speed of sound. This will likely be a low-power coilgun that fires metal pellets fast enough to penetrate three inches of wood at best.

Note, a coilgun is not a railgun, and have nothing in common except that things come out the end of them.  And electricity.

[Duke 2.0]

I really don't think an amateur in his backyard will make anything terribly powerful. The whole magnetic rails dissolving things only applies to massive powerful railguns that fire at several times the speed of sound. This will likely be a low-power coilgun that fires metal pellets fast enough to penetrate three inches of wood at best.

Note, a coilgun is not a railgun, and have nothing in common except that things come out the end of them.  And electricity.

From what I understand, both use electromagnetism to drive a metal slug out of a barrel. They just use different electromagnetic laws to drive the slug down the barrel.