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Dual Stage Coil Gun From Longshot

kind of a railgun

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#1 MrDelish

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Posted 30 December 2008 - 02:23 AM

Note that I do not take credit for this, as it was made by a member of another forum I frequent and he has yet to be validated:

Nerf Longshot: Dual Stage Coil Gun

This started out as a Secret Santa gift. I had no idea what to get the person and saw that they both A: liked nerf weapons and B: liked Tesla, so I figured I would combine both into one. It is a dual stage electrokinetic coil gun that fires 3 inch steel bolts.

The list of parts required are:

1 Longshot

1 Barrel - Polycarbonate tubing. Can not be copper because of eddy currents. More on this later.

2 Heavy duty solenoids, 24v continuous use rated. ( you can wind your own coils if you want, but this is the easiest way to make sure you have uniform windings)

2 Switches- one for main power and another to fire

1 charging circuit

2 capacitor banks

1 8 AA battery pack (12v)

High voltage diodes

Rolled steel rod to mill into ammo


For basic coilgun theory here are some useful websites.
http://www.coilgun.eclipse.co.uk/
http://www.powerlabs.org/gaussgun.htm


First thing first. The way I did it is not the optimal way for power, but was by far the easiest. It is a pain in the butt to fit the circuitry in the case. I could have used an infrared sensor as an optical trigger, but it would have required even more wiring and I simply didn't have the patience for it.

Basic Overview

Posted Image

The battery clip (J) is modified into the existing longshot clip so it can slide into place. It is connected by the battery terminal (K). The power switch is on the outside of the case, above the trigger and behind the clip release. When this is switched on it completed the circuit and allows the batteries to power the charging circuit (H).

The charging circuit is a CCFL driver that takes the 12vdc input and outputs it at 350vrms (voltage root mean square). What this means is that it is outputting pulsing DC, rather than continuous. This is necessary in order to multiply it further with a cockroft-walton multiplier.

This now high voltage current is led to a charging relay (G). This relay is simply a piece of perf board to make leading it to the banks easier. From here, using diodes, it is sent to both capacitor banks (A and I). The average charge time was 1:30 minutes, but the CCFL driver is the limiting factor. During tests with a flyback driver from a TV it charges much faster. I had to use the CCFL in order to save space.

The capacitor banks are flash tube or camera capacitors. Each have a 120uf -160uf rating at 330v. The first bank is 990v @ 160uf, the second is 1320v @ 60uf.

The capacitors are both connected to switches. The primary coil (F) is controlled by the switch that replaced the trigger. When fired, the electricity shoots through the coil creating a very strong and very short lasting magnetic field. It must be short lived (controlled through total capacitance of the bank) because if the field is still "active" when the bolt passes through it, it will be sucked back into it.

When the bolt reaches the secondary, it is fired by switch C. This is a very pressure sensitive micro touch switch. The bolt hits it and it completes the circuit, allowing the secondary coil to fire.

Resetting the primary trigger enables the charging to begin again.

The final gun had a iron flux guide installed over the secondary coil. Due to sheer idiocy on my part I put the trigger too far away from the second coil and the bolt was rather unaffected by the field. By putting a cylinder of iron or steel around it and leading back further, I was able to guide the magnetic flux back enough to "grab" the bolt.

Modifications to the LS body itelf was just the removal of everything inside except for the clip lock and then LOTS of plastic removal to make it fit. I also permanently attached the stock for more space.


Test video of just the first coil. http://s258.photobuc...ticalLaunch.flv

Completed gun test vid (you can see the modded battery clip pretty well in this, along with how it is loaded ( in the rear with a magnetic "ramrod" that holds the bolt in place behind the tub in the optimal position)
http://s258.photobuc...nt=TestFire.flv


At this time there are no range measurements nor indications of what it can damage/pierce. I just asked, and may get something soon, though I'm pretty sure he's already given it away.
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#2 Forsaken angel24

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Posted 30 December 2008 - 02:37 AM

Someone fast track this member asap.

This thing fires 3" steel bolts? Is there anyway to make it fire stefans? Maybe with a steel ball bearing instead of a lead fishing weight?

Edited by Forsaken_angel24, 30 December 2008 - 02:38 AM.

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#3 sputnik

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Posted 30 December 2008 - 02:41 AM

Holy Fuck.
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#4 boisie

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Posted 30 December 2008 - 02:51 AM

Time to build it.
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#5 AssassinNF

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Posted 30 December 2008 - 02:54 AM

Someone fast track this member asap.

This thing fires 3" steel bolts? Is there anyway to make it fire stefans? Maybe with a steel ball bearing instead of a lead fishing weight?


If this is like most coilguns I've seen, it would fire the dart at speeds which would cause serious injury to the victim.

That is, if the ball bearing stayed in the dart...

It would probably rip the bearing right out of the dart and fire that.

And I bet those 3" steel bolts can cause some serious damage. :)
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Probably dead by now, or something.


#6 Fome

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Posted 30 December 2008 - 03:39 AM

As cool as all hell as this is, I'm afraid that firing steel bolts at extreme velocities is a far cry away from what nerfing is all about. Nerf is fun because you can shoot at people and they... you know, don't die.

For a more foam friendly version, is there anyway to engineer the magnetic field to propel a steel plunger head through a tube instead, effectively allowing it to shoot foam darts?

Still... coooool.

#7 xtremejumpy

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Posted 30 December 2008 - 10:32 AM

Maybe you could fire stefans with washers. You might be able to cut it down to one relay, but have a stock a2k blast to get it there. Maybe have the power of a BBBB. Still, if you could get us ranges, and let us know how stefans go, we could probably help make it "people freindly"

Always wanted a coil gun...
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#8 PointBlank

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Posted 30 December 2008 - 10:52 AM

Holy shit! Your a genius! this has got to be the most powerfull/deadly nerf gun I have ever seen!

Edited by PointBlank, 30 December 2008 - 10:53 AM.

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#9 MrDelish

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Posted 30 December 2008 - 12:30 PM

As cool as all hell as this is, I'm afraid that firing steel bolts at extreme velocities is a far cry away from what nerfing is all about. Nerf is fun because you can shoot at people and they... you know, don't die.

For a more foam friendly version, is there anyway to engineer the magnetic field to propel a steel plunger head through a tube instead, effectively allowing it to shoot foam darts?

Still... coooool.


He obviously didn't make it with the intent of bringing it to a nerf war, you goon
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#10 umpshaplapa

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Posted 30 December 2008 - 12:48 PM

As cool as all hell as this is, I'm afraid that firing steel bolts at extreme velocities is a far cry away from what nerfing is all about. Nerf is fun because you can shoot at people and they... you know, don't die.

For a more foam friendly version, is there anyway to engineer the magnetic field to propel a steel plunger head through a tube instead, effectively allowing it to shoot foam darts?

Still... coooool.


He obviously didn't make it with the intent of bringing it to a nerf war, you goon

Dude calm down. He complemented it and even gave you a suggestestion on how to make it fire foam.
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#11 MrDelish

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Posted 30 December 2008 - 02:26 PM

Like I said in the OP, it isn't even mine, and I meant "goon" in a more playful manner than a snide one.

you goon
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#12 eddieoctane

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Posted 30 December 2008 - 02:28 PM

Someone fast track this member asap.

This thing fires 3" steel bolts? Is there anyway to make it fire stefans? Maybe with a steel ball bearing instead of a lead fishing weight?


Seconded. Although this guy may just use an army of robots armed with coil guns and take place over.


That thing is both awe inspiring and terrifying. It's probably pretty close to being lethal, and I doubt the gov't has any idea people can make their own coil guns when the Navy is just testing a prototype rail gun now.


One though on my part: would it be possible to have the coils (excluding the primary) fired off a timing circuit? If the bolts are fairly uniform and the electronics aren't crap, the forces should be relatively predictable. If a timer could set off each subsequent coil after being started with the trigger, the bolt wouldn't have to contact any switches and potentially alter it's flight path. And in case anyone was curious, there is a difference between a coil gun (like this monster) and a rail gun. They both use electromagnetism to propel a projectile, but use different means to generate the field.
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#13 TantumBull

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Posted 30 December 2008 - 03:28 PM

Of course the government know people know how to build gauss guns and electromagnetic railguns. if they were as reliable and had the rate of fire of modern firearms then they would probably be used. We are at the point of our understanding of rail and coil guns that we can really only make larger weapons out of that technology, like for use on navy ships. Hand held rail guns and coil guns wouldn't be practical at this point in time.
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#14 Mr BadWrench

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Posted 30 December 2008 - 05:34 PM

I made a railgun as a science project when I was in school, got to go to a big summercamp for nerds. Im pretty sure I still have all the parts...
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#15 Demon Lord

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Posted 30 December 2008 - 07:23 PM

Someone fast track this member asap.

This thing fires 3" steel bolts? Is there anyway to make it fire stefans? Maybe with a steel ball bearing instead of a lead fishing weight?


A steel ball bearing might survive the force of being shot out of that beast, the stefan it was in on the other hand may not...
However not knowing the range or the force that the bar hits with limits my guessing.
One of Captian Slugs washer stefans might have a better chance of surviving being launched if something other than hotglue is used to secure the washer on.
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QUOTE(VACC @ Mar 7 2011, 09:03 AM) View Post

Don't worry so much about what other people will allow. Throw your own wars and kick your friends' asses until they all want one.

#16 zadjii

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Posted 30 December 2008 - 09:54 PM

Someone fast track this member asap.

This thing fires 3" steel bolts? Is there anyway to make it fire stefans? Maybe with a steel ball bearing instead of a lead fishing weight?


I third that.
I fourth it, fifth it and sixth it. But seven times is too many for me.


So building this with my nerd friends in engineering next semester. *evil snickers* =P

Oh and did I forget the OH HOT DAM!
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#17 battle12

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Posted 31 December 2008 - 12:31 AM

I don't think this would be aloud in nerf wars even if you converted it to fire nerf darts. Steel bolts flying at high speeds at me make me uncomfortable.
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