Making a rail gun (again!)

[Rp181] is at it again with version 2 of his rail gun project. The original did have some power with 18 400V 3900uf capacitors, but he’s ramped it up to now using 40! Reaching more than double the amount of joules of energy, 12kJ vs. the 5.6kJ! Some other changes include a new injector solenoid setup and revision 3 of his breakwire chronograph. Sadly, he doesn’t mention if this is as green as his first rail gun. Check out a video of just the injector firing and an animation explaining some new updates after the jump.


  1. amodedoma says:

    Is it just me or does 12kj, sound ridiculously dangerous to be playing around with!?

  2. medix says:

    5.6 vs 12 kJ doesn’t make much difference in terms of hazards really. You’ll still be thrown across the room and (possibly) loose a digit or two if you do it right.

  3. Mirlotus says:

    Nice capacitors array!!!

  4. Taylor says:

    Stupid question. What are the magnets at the end for?

    I’ve been wanting to play around with one of these so I am curious.

  5. Ravi Gaddipati says:

    Hello all:
    If you have any questions, email me

    The animation is poor in telling what the end product will be, I changed LOTS of things. The best thing is to read the build log V2 category on my blog.

    medix is right. The voltage is exactly the same, so unless your clamping your body parts to the capacitor bank, you would react long before the bank discharged.

  6. Ravi Gaddipati says:

    Oh, and I never was really serious about the “green” comment. Lets face it, its just awesome!

  7. medix says:

    Nice work Ravi. Reminds me I have alot of un-finished projects lying around (similar to this one).

  8. David says:

    Ravi, where did you get those capacitors?

  9. Ravi Gaddipati says:

    alltronics, but they ran out, as did every other place carrying them.

  10. exiledbear says:

    I find the use of that many high value capacitors disturbing.

  11. Dajjhman says:

    Looks good Ravi! – make sure to send mr video of what it dies to the bullet proof glass I sent ya!
    maye we can compare results when I get mine built in a couple months for my senior project.

  12. Ravi Gaddipati says:

    yep! Im making a mount for them soon, either with welded steel, or PVC pipe I molded. The hard part is getting the railgun lined up with the chronograph (with sufficient distance to disperse some plasma), then the relatively small target, with room to record. I should be able to record with at least 2 cameras (one HD), and hopefully the high speed.

    I will probably do a single 3″ square piece as the target. I expect to fire on the 14th or 21st.

  13. Roly says:

    I love this! It’s so OBVIOUSLY suicidal it’s charming. {OP doesn’t have a cat or dog (any more) I presume}

    You could always fall on it I ‘spose if you wanted the full effect.

    Mind you, old spark transmitter stations had banks of oil-filled mica caps that would put this in the shade. Just a dinky little wooden handrail between you and instant vapourisation – one flash and you’re ash.

    To the point; good electros can be had free from your local computer repair shop in “dead” power supplies, free for the asking. They can also be recovered from photoprocessors in used disposable flash cameras, also free for the asking. More;

    “I hate to advocate drugs, alcohol, violence, or insanity to anyone,
    but they’ve always worked for me”. Hunter S. Thompson

  14. AJ says:

    Is that Audacity? More info on using Audacity as an analisys tool please!

  15. Ravi Gaddipati says:

    That is audacity, a PC microphone port was used to record that.
    see :
    you just get a microphone cable, and connect it to any (LOW AMPLITUDE, +/-1 volt) source, and record.

  16. Manveru says:

    @Taylor (Magnets):
    The projectile is pushed forward due to the interaction of the current through the projectile and the magnetic field of the rails (generated by the current in the rails). Increasing the magnetic field will also increase the acceleration of the projectile.

    Therefore I would even recommend magnets above and below the rails for better performance.

  17. Federal Firearms License Application says:

    Great Post! I admit that I’ve never looked at it that way before….

  18. Ravi Gaddipati says:

    the animation is outdated, I came up with a optimal config using FEMM, the bore will have magnets on all 4 sides.

  19. josh says:

    ARE the neodeium magnets arranged in halbach arrays?

  20. Ravi Gaddipati says:

    I don’t have enough magnets to do halbach arrays, but I would love to try them.

  21. Connor Bacon says:

    Hey guys, I am competing against ravi in rail gun design. I have one rail gun built so far that is very similar to his but has many noticeable improvements(15-18kj for one haha). I will be building a new and very improved model with the next two months.

    I don’t have a site (I’ve been too busy to make one)but I do have a flickr you can check out.

    I have not updated it in the last few weeks (again to busy) but I will update it very soon.

    Good luck on your Thursday shooting Ravi!

  22. Dartanyin says:

    what is the range on this thing

  23. Anonymous says:

    Anyone have a link? The blog is no longer up.

  24. Beemer says:

    Nice design, but what is the air tank for(if that is an air tank)?

    SUggestion for future project… As i am currently building one myself, with 40 x 1.25 farad car audio caps:

    – If you are using an airfoil-type projectile ( ring shaped), put a rotation in the rails- like a 180 degree roatation per 2 feet. Theoretically (havent tested yet as i am not finished), the roatation combined with the air-foil projectile will dramatically decrease drag and increase stabilty and energy.

    However, i also am using the capacitor bank with another rail setup to experiment with projectiles traveling at appx. 75% the speed of light in a continuous circle… Experiment with hyper-velocity megnetic induction and disturbance with opposing poles. SO far i’ve melted a few rails since the speeds cause enormous friction.

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