Magnetic Linear Accelerator

Magnetic Linear Accelerator

Magnetic AcceleratorThis experiment is a simple way of demonstrating the distribution of the field inside a solenoid and how it effects ferrous metal objects.

This experiment simply consists of a plastic or cardboard tube with a coil of wire wrapped around one end. The coil can be powered by a set of standard batteries. the more batteries used the more powerful the magnetic field will be.

The tube used to for the coil around should be quite narrow. The case of a pen such as a biro is ideal. You can try using different sized batteries and different numbers of turns on the coil to produce different strength fields.

When a metal object is placed part way into the coil it is ready for firing. The metal should be ferrous (sticks to a magnet) and quite small. A metal rod of about 2 – 3mm wide and 10 – 20mm long is best. Something like a small nail or a screw with the head cut off should work fine. If a small rod magnet is used, it will work much better but make sure it’s inserted the right way around, or it could backfire.

To fire the coil gun you simply tap the switch. If you press it for too long, the projectile will either stop in the middle or come back out the wrong end. You can practice different methods and different coil and battery sizes to see what results you get. An alternative firing method would be to use a circuit such as the PWM-OCX which can give repeated pulses or a time you can set yourself.

For higher speed projectiles, it is possible to  use multiple coils and fire them in sequence so that each one will further accelerate the projectile. Each successive pulse must be shorter than the previous one due to the projectile spending less time in the acceleration region. If the pulses were too long, they would drag the projectile back, slowing it down. Our 3 channel time delay generator could be used for controlling the pulse timing to a transistor on each coil.

19 Comments

  1. RMCybernetics

    Closer is better. More turns is better.

  2. Adil doe

    Is it more efficiant to have the coil wound up closer together?
    and.
    How many winds per inch?

  3. RMCybernetics

    Lantern batteries will not give you much current at all and will only allow you to fire a very small projectile. You need something like an SLA battery

  4. Flynch

    Mats: heavy plastic barrel, 18gauge solid copper wire, two 12volt lantern batteries connected parallel.

    Tried running the batteries in series as well.. Tried 12 and 25 coils.

    I can’t get it to fire.. Any suggestions?

  5. RMCybernetics

    Maybe, it depends on many things. You will need to choose your trigger switch well or it will just fuse together from the heat.

  6. zander

    i am planning on launching a three inch long and1/2 ” diameter piece of round stock steel through a piece of pvc, havent constructed this yet, but i am wondering, would four 12 volt 750 cranking amp car batteries ran in a series using 8 guage wire wrapped about twenty times work well?

  7. RMCybernetics

    No, The device works based on current pulses. Such a device makes high voltage, low current.

  8. Ben

    I’m building a sectorless wimhurst generator for a school project. Could an accelerator like this be positioned in the spark gap to work when the generator discharges?

  9. RMCybernetics

    Science Fair Dude,
    Use non metallic items except the wire to build it. Batteries should be physically large (they can give more current) and at least 9V.

    John,
    At least 10 times. If the projectile stops in the middle it is because you dont release the switch fast enough. You must disconnect power before it reaches the middle or it is pulled back again.

    Thick Wire

    Larger batteries would be better.

  10. John

    I have a couple of questions.

    1. How many times should I wrap the wire around the tube? I wrapped it around once but nothing really happened (the projectile was pulled into the middle of the wire.)

    2. Should I use thick wire or thin wire?

    3. I’m using two 9volt batteries. Should I use more batteries?

    Please answer, Thanks.

  11. Science Fair Dude

    Hi, I’m doing my science fair project on this and I’m just wondering what kind of battery should you use? Oh, and another thing if I use a metal ring to hold the wire in will it affect it in any way? Please answer. Thanks!

  12. RMCybernetics

    Why can’t you, do you have a problem with the ordering system? All prices are in £ GBP because this is an English company in England. You can pay in USD and it is automatically converted. If you want to know the price of something in USD you should check the current exchange rate.

  13. wildguy

    can you get more items in the shop because i can’t buy anything.And also can you make the prices for the items USD?

  14. RMCybernetics

    Make sure screw is ferrous (will stick to a magnet).
    The accelerating force is proportional to the current flowing in the coil. What type of batteries are you using? how thinck is your wire?

  15. wildguy

    i have a problem.I have a straw as the barrel,i wrapped the wire a round the straw 12 times.i have a push switch and four batteries in a battery holder and i connected it the wires.and i have a screw as ammo,but it doesn’t work,do you know why?

  16. HI

    Can someone tell me how to connect the battery and the wire and the switch?
    Thanks.

  17. Commodore

    I tried this few years back with said Biro and wire, great fun, keep meaning to find a long tube and rig up light sensor / reed switch to cut the power before the 1/2 way point.

    Odin, sounds like your wire is too thin (I used speaker wire, as it was lying around) but I think solid core bell wire is better idea. While u need the wire to be insulated, it needs to be fairly thin. Oh and it aint a metal ballpoint tube is it?

    Again, should be obvious, but your coil is most effective when it’s tightly wound with as many turn as possible for a given distance of tube and you can only coil in one direction.

  18. RMCybernetics

    The metal object is attracted to the middle of the coil. The power must be disconnected just before the projectile reaches the center to prevent it from being attracted back again. Just a quick tap of the switch is all that’s needed. One AA battery might be too small, 3 to 6V should be enough.

  19. Odin

    I have tried doing this using a ballpoint pen tube and a small magnetic cylinder.
    But when ever I connect the power supply( one AA battery) all that happens is that the wire coil heats up and the magnet jerks inside the tube….
    What could be the problem? Should I try using a higher volt battery?

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