I have x components, can I make a railgun?

Discussion in 'Homework Help' started by rezky, Apr 27, 2014.

  1. rezky

    Thread Starter New Member

    Apr 27, 2014

    I was given a physics group task to make something involving electricity <-> magnet conversion.

    Somehow we decided to make a miniature railgun but then we got stuck :(

    Here're the components we have:
    > A pcb/circuit board consisting of two 450V AC capacitors and two diodes.
    this is supposed to be an AC to DC converter used to charge the capacitor bank and we got it to pump 220V to the caps

    > two 450V/680uF capacitors in parallel as the capacitor bank. as I said, it can be charged to 220V by the pcb (converter?)

    the capacitor bank will be connected to the rails with a switch between them.

    the problems are:
    1. how long should the rail be
    2. what should be the projectile (we are considering ball of alumunium foil)
    3. is that amount of power enough for a railgun at all?

    please help us, guys. I'll really appreciate it!
  2. nerdegutta


    Dec 15, 2009
    Have you read the ToS?
    Code ( (Unknown Language)):
    2. 6. Restricted topics. The following topics are regularly raised however are considered "off-topic" at all times and will result in Your thread being closed without question:
    3. Any kind of over-unity devices and systems
    4. Automotive modifications
    5. Devices designed to electrocute or shock another person
    6. LEDs to mains
    7. Phone jammers
    8. [B]Rail guns and high-energy projectile devices[/B]
    9. Transformer-less power supplies
    I'll guess you're on your own...
  3. WBahn


    Mar 31, 2012
    I realize that you are talking about a toy-scale rail gun for a physics demo and not something that is high energy, but it still technically violates the ToS.

    One thing that you could do that uses the same concepts but shouldn't violate the ToS is to build a penny launcher. This is basically a coil that you set a penny or dime on top of and then hit a button to dump the energy from some capacitors into the coil. At room temperature you usually find that the coin barely jumps (1/8" to 1/2" or so), but if you cool the coil and the coin to liquid nitrogen temperature you can get it to jump several feet (we regularly bounced dimes off ceilings when doing demos).
  4. bertus


    Apr 5, 2008

    There are two ways this would violate the ToS.
    1 ) A railgun.
    2 ) A transformerless power supply.

    Take the advice from WBahn to make a coin flipper and use a transformer in the power supply.

  5. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    The capacitors, used as you describe, hold a LETHAL charge. You should not be doing this unless you are competing for a Darwin Award !
  6. Papabravo


    Feb 24, 2006
    The truly sad thing about winning a Darwin Award is that you will never know about it since they are awarded posthumously.
  7. bwilliams60

    Active Member

    Nov 18, 2012
    What is the age of this group you are dealing with and when is this project due?
  8. rezky

    Thread Starter New Member

    Apr 27, 2014
    Whoops, I see. Sorrry about that.

    Maybe I shouldn't say it, but I wouldn't have learned that any other way. I'd be careful if I'd ever post again.

    Thanks for your advice. I'll look up for it. :)

    lol! :)

    Well, I guess it was reasonable that this project being quite impossible for several reasons. Safety included.

    To be honest, I was quite clueless about the possible harm >hundreds voltage could have. I should have mentioned that it was a college project, and I wasn't an electrical engineering student (it's a physics project, see). We were inspired by videos on the internet and our senior approved it so I thought it was okay.

    Oh, when I said clueless, no worries about it being completely harmful since no one permits themselves to touch a charged capacitor anyway (we've seen 'em exploding when discharging them. I kind of understand why it would be lethal)

    On related note, what kind of voltage would be considered safe? (when talking about capacitors)

    Otherwise, feel free for the mods to close/delete this topic.

    Thanks for the replies.
    Last edited: Apr 28, 2014
  9. WBahn


    Mar 31, 2012
    Not always. Remember, the rule for qualifying is merely that you remove yourself from the gene pool. A number of people have found ... creative ... yet nonlethal ways of doing that. :D
  10. #12


    Nov 30, 2010
    Speaking from a National Electrical Code point of view, 50 volts peak is considered low voltage. You can still get some painful lessons from 50 volts, but it won't blow your fingers off unless you really try.
  11. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    I feel obligated to point out that 50v contained in large capacitors (if accidentally shorted out) can release enough energy to turn the end of the screwdriver into a molten metal projectile that CAN blow your fingers off.

    When i worked in industry an electrician pushed a high current HV breaker back into place when the busbars were live, the resulting explosion of molten copper and plasma blew most of the flesh off the poor guy's forearm. It was an amputation level of damage. As in amputation was the cure for the damage. :(