SpudFiles

Behold!


I've had this thing functioning for over a month now and only just got the capacitors I needed to finish it (Thank you, random woman at Giant Eagle). It's a single stage gun, but it seems to be in a butter zone of sorts, having (relatively) high output power for all the bigger it is.


So, instead of more rambling, specs:

Weight: 11 oz
-Muzzle velocity: 65 FPS (calculated using the stopwatch method, probably underestimated due to drag)
-Muzzle energy: 2.2 joules

-Capacitor bank: 10 low-ESR photoflash caps, MAX 60 joules capacity (normally runs about 50).
-Charger: Two lightly-modified camera flash chargers
-Charge time: 30 seconds with semi-decent batteries, but letting it run for a couple minutes seems to boost power 10-20%.

Other features:
-Adjustable magnetic breach loader, keeps the projectile from falling out when shooting downward.
-Charger light that stopped working for no reason.


This gun was designed to be as compact as possible, and can fit in most loose pockets. Looks a little too threatening for classroom use, unfortunately (would probably make someone dive under a desk if you pointed it at them:).

I don't think it could do much more than put an eye out, so it's relatively safe, but the capacitor bank still has enough juice to kill you multiple times when it's fully charged.

But anyway, I can make holes in pop cans, so I'm happy for now.

Youtube video:
[youtube][/youtube]

thats a beast

Very nice. I have been expecting something this nice.

Its a very good build and the paint job and egronomics are nice as well.

A kid tries to shoot a spit ball at you and you pull out this, lol.

_Fnord says to kid with spitball shooter: "Drop it."

That's pretty sh!te power but it's not all about the footpoundage, props for making it work

Wow... the power is irrelevant to me; its the good looks that do it! Great job!

Dang that looks really nice. I was trying to make a coil gun not long ago but I ran into couple of problems. Did you use an SCR to trigger or did you use the flash bulb method? And how did you connect the 2 charging circuits parallel or series? How did you get it to run on 2 batteries instead of 1?
When I was making my gun I had 6 flash caps and I wound my coil and etc. I soldered 2 exactly the same charging circuits that worked by them selfs but then when I connected 2 AA batteries nothing happened at all. They run on 1 AA battery each so I figured it shouldn't fry on 2 since I got them in parallel. I guess I was wrong. Is there a resistor I can change to allow for higher voltage or do I need to change the transistor. Today I'm going to go to Wal-Mart and go get some free cameras. I heard if you ask them for the ones they already used they'll give them to you. Thanks for your help.

Thanks everyone. To answer your questions Felex,

1. No SCR or flashbulb, just a manual switch. I can't imagine it's causing a large loss of power since the efficiency is around 4-5%, which is about the max for current coilguns.

2. The flash circuits are in parallel, and each has it's own battery. Every time I try to put higher voltage into a flash circuit I end up frying it.
Also, sometimes they don't work if you have more than one flash running off the same battery. This may be your problem.

Wal Mart may not give them to you, as big companies have to worry about more legal crap like that.
You can probably get them from a pharmacy or something.

Hey thanks a lot. But doesn't high voltage fry your switch. Thats what I had on my very first gun but the switch would fry every couple of shots. What store can I go to to get some one time use cameras. Would Wall Greens have them?
EDIT: Oh and you could use the SCR thats on the flash circuit couldn't you? Its the little green knob thingy with the white wire coming out of it.

Wow... it looks familiar for some reason. Looks like a gun off Judge Dredd or something. Just mount a laser on the bottom of that box near the muzzle and you could pass it off as a Star Wars blaster, or a taser.

I say your next project should be an electrothermal gun. I've read too many horror stories from people trying to build railguns.

Blast, I was beaten to it. I've had gauss pistol plans for a while.
It's the secret project I've been occasionally been dropping mysterious hints about. It's still in a planning stage, but it's looking like it should turn out quite well.

The thing with gauss pistols is that you can build quite complex designs quite small. I'd never be able to make any self-contained semi-auto air pressure based launcher of equivalent power for what I could with gauss tech without full machining capacities. And any onboard supply wouldn't last half as long.

I think electrothermal or electrochemical would be a better choice than a railgun, because unless you can master plasma armatures it will need regular rebuilds.

@ Felex: no, my switch is fine. It's a PSU power switch but it seams to take high current load pretty well.

You should probably be able to get the from wallgreens. Try using the "science project" line at the photography department, they might give you a box full of them or something.

I believe the part you described on the flash circuit is actually a transformer. They just use the two copper prongs for a switch.


@Ragnarok: Thank you for sharing your current and future projects, but this is a thread about the aforementioned gauss gun

I may try an electrothermal gun, but I just got access to rail material so I wanted to throw that out there too.

_Fnord wrote:WalMart may not give them to you, as big companies have to worry about more legal crap like that.
You can probably get them from a pharmacy or something.

It's not really a legal issue, more of a monetary/green issue. Large companies are actually recycling camera bodies. Possibly they strip the stickers off, replace a battery and add new film and send the unit out again after a quick ops check, then sell them in a 3rd world country or just recycle the plastic. Who knows how they do it, but a lot of pharmacies are not giving out cameras any more because of this.

What windings did you find work best? My current one has 4 layers of about 20 coils each( which by the way shoots through two pieces of paper at 23J )

_Fnord wrote:@Ragnarok: Thank you for sharing your current and future projects, but this is a thread about the aforementioned gauss gun.

You are quite right. Sorry about the thread hijacking, I've hacked the offending post down to a less obtrusive length.

I meant to ask about what you're using as a projectile.

Video now up!

rp181: I'm using about 10 layers of .035" magnet wire, with around 30 turns per layer.

Ragnarok: Well, it's ok. I enjoy hearing about your projects anyway.

In the video I was using a bit of allen wrench. It weighed somewhere around 10 grams I think (can't find it now).
Other than that I just use bits of welding rod.