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Low voltage rail guns

athon

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Does anybody know if it's possible to make a low voltage, simple rail gun? I don't know enough about Lorentz forces to know it's possible to make a simple circuit that could move a projectile at a low velocity. Basically I want it to demonstrate the concept of a Lorentz propelled object, rather than actually send a projectile at high speeds.

Not to say I wouldn't love to make a high speed one, but for my purposes it needs to be simple and safe. LV battery, no comulsator...that sort of thing. All I can find on the net are instructions on making the bigger ones.

Athon
 
Sorry, but I do not think that it is possible to make a low voltage rail gun. However, if anyone has data to the contrary, please post it.

Perhaps a more conventional way of accelerating projectiles would be better for you.
 
I'm making a school show on magnets. I'm planning on making a small electronic motor as one way to demonstrate the Lorentz force, but like the idea of making a rail gun to make something light move along a set of conductors. It'd be a question of safety and practicality more than anything. Although I'd be the only one operating it, I still don't want anything too powerful (well, past a car battery, for instance). And I don't want to be launching projectiles at high speed (insurance won't cover 'death by rail-gun' for the students, although it would be kind of fun).

I've never sat down and done the maths on the minimum currents needed. I know for the bigger ones you need to start building things to concentrate magnetic fields and increase the forces through controlled bursts (as in a compulsator), but I also don't know if small ones are possible.

I hope so. It'd be cool to make one. I just don't want to go to the trouble of experimenting if somebody who knows the theory says it can't theoretically be done.

Athon
 
Athon:

You might be better off looking at something like a train set-up.

You could use a small toy train and track, and work on moving it back and forth. Low-speeds are more-or-less what you want from this, and it might be easier to work (as you don't actually have to launch anything, just move it). The fact that it'll roll will help, as well :)
 
What about something like this? He's suggesting powering it with 2 9v batteries. Although he hasn't tried it himself, some lass from Carnegie Mellon University has, and she reckons it works fine.
 
Well not to side-track things, but I am a volunteer Aerospace Education teacher myself and one of the things I cooked up was a compressed air and water 2-liter rocket launcher.

The kids really liked it!

It made a good noise, made a mess, and shot something into the air.

It also demonstrated several good principals because it allowed one to control the amount of fuel (in the case the water),
The potential energy of the fuel (in this case the air pressure and air volume),
And some of the aerodynamic variables (which could be altered by adding mass, nose cone, fins, etc).

The kids found out in short order that one must balance the amount of fuel with the amount of pressure in order to achieve maximum height.

The adults liked it since it was safe, fun, diverting, and quite educational.

I can provide more details if you like.
 
athon said:
I'm planning on making a small electronic motor as one way to demonstrate the Lorentz force, but like the idea of making a rail gun to make something light move along a set of conductors.
Click to expand...

Have you considered a flux torus launcher? (aka: Thompson's Flying Ring - demonstrates Faraday's Law)

http://www.physics.montana.edu/demo...tyandmagnetism/demos/thompsonsflyingring.html

You can get good height with enough flux. Safety first. These were considered a credible orbital launching technique for awhile.
 
athon said:
Does anybody know if it's possible to make a low voltage, simple rail gun? I don't know enough about Lorentz forces to know it's possible to make a simple circuit that could move a projectile at a low velocity. Basically I want it to demonstrate the concept of a Lorentz propelled object, rather than actually send a projectile at high speeds.

Not to say I wouldn't love to make a high speed one, but for my purposes it needs to be simple and safe. LV battery, no comulsator...that sort of thing. All I can find on the net are instructions on making the bigger ones.

Athon
Click to expand...

Is 110 VAC low enough voltage for ya?
How about a MHD Drive? It's basically a railrun that uses water as the projectile.

I've made a couple of these in my day, running directly off the wall outlet. With enough coils in your electromagnet you can pump a fair bit of water. It's not as effecient as a propeler or impeller, but with no (obvious) moving parts it can be impressive to kids.
 
Crossbow said:
Well not to side-track things, but I am a volunteer Aerospace Education teacher myself and one of the things I cooked up was a compressed air and water 2-liter rocket launcher.

The kids really liked it!

It made a good noise, made a mess, and shot something into the air.

It also demonstrated several good principals because it allowed one to control the amount of fuel (in the case the water),
The potential energy of the fuel (in this case the air pressure and air volume),
And some of the aerodynamic variables (which could be altered by adding mass, nose cone, fins, etc).

The kids found out in short order that one must balance the amount of fuel with the amount of pressure in order to achieve maximum height.

The adults liked it since it was safe, fun, diverting, and quite educational.

I can provide more details if you like.
Click to expand...

Already doing it. :)

In fact, the CSIRO kit I'm writing for at the moment (and illustrating!!!) focusses on the water rocket. I went out on Tuesday afternoon and played with it for several hours. Soooo much fun. I also had to develop several activities kids could use to do it, as well as other things to put into the kit which could explain Newton's laws (like rocket balloons and stuff).

Athon
 
GodMark2 said:
Is 110 VAC low enough voltage for ya?
How about a MHD Drive? It's basically a railrun that uses water as the projectile.

I've made a couple of these in my day, running directly off the wall outlet. With enough coils in your electromagnet you can pump a fair bit of water. It's not as effecient as a propeler or impeller, but with no (obvious) moving parts it can be impressive to kids.
Click to expand...

Hmmm...could be wicked. Could you PM me what I'd need to make one? After more looking, I don't think I could get a battery-powered rail-gun to fire without overcoming some complications.

Athon
 
Without having yet followed the other responders links, I think it is the current and not the open-circuit voltage that counts.

Assuming low enough loop resistance and sufficient source current availability, I think it's all about the amps.:) (or ampere-turns, but rail guns are mostly 1 turn devices)

But I could be full of manure.:D

Cheers,
Dave
 
No, that makes sense, however to get the current up, you need higher voltage and lower resistance. Resistance only goes so low, unfortunately, which means pumping up the volts to get a large enough magnetic field.

I can dream, though. One day I'll have a back shed, and enough stupidity to go ahead an build one.

Athon
 
athon said:
No, that makes sense, however to get the current up, you need higher voltage and lower resistance. Resistance only goes so low, unfortunately, which means pumping up the volts to get a large enough magnetic field.

I can dream, though. One day I'll have a back shed, and enough stupidity to go ahead an build one.

Athon
Click to expand...
"Room temp." superconductors and mercury contacts? Yeah, one can dream.:D

Dave
 
They have a "rail gun" at Magic Kingdom at Disney World in Florida, which has likely transported ten million guests almost a mile in one ton projectiles = 4 passenger cars at speeds of at least 6 miles per hour = 10 kilometers per hour. The voltage is likely about 250 volts at 40 amps per car, so 25 volts at 400 amps should work just as well, except much heavier wiring is needed. The cars run on narrow gauge train tracks with electro magnets spaced about 1.5 meters apart between the rails. The system has operated for 30 years without a major retrofit. I presume the magnets are energized sequentually to propel the cars. A scalled down version could be powered by a 12 volt car battery size deep cycle battery for each magnet, with a relay to turn the magnet on and off. Sorry, I have no more details. Neil
 
I'm not sure it's a real rail gun, Neil. By the way you've described it, it sounds more like a mag-lev train. Making one of those would be easier power wise, but tricky to get the circuitry built properly. I'm not that much of a sparky that I would go to such lengths to make one of those, I'm afraid.

Athon
 
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