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full auto weapon

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#1 FoamSniper

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Posted 22 March 2006 - 12:26 PM

I'm building my first weapon from scratch, I've modded several, but this will be a learning expirience since I've never done anything with this type of firing mechanism. All my mods thus far have involved compressing air either by plunger or pump/airtank.

I'm designing a clip fed full-auto weapon, using two spinning disks to launch the darts (micros/stephans). The disks will spin constantly, regardless of whether or not the weapon is being fired (on/off switch to save on battery life). The trigger will simply be a catch that prevents darts from being put into the chamber. The clip will be a vertical feed, not a tube feed. When the trigger is depressed, it removes the catch and puts the front edge of the dart into the disks. I originally had a more complicated design, but the more mechanically complicated something is, the more likely it is to break... or just not work to begin with.

I haven't found as much info on spinning disk designs as I have for other designs, so I thought I'd post a few questions.

I'd like to know if anyone has any recommendations for how far appart my disks should be? If it matters, I'll be using toy car wheels, with rubber grip, and are 2.5" in diameter. Obviously I'll want to have them close enough to put a little bit of a bind on the dart in order to fire it, but far enough away to not squish the dart. I was hoping to skip some guess work.

Also, I cannot locate anything on a recommended barrel length for a spinning disk setup. I'm aware that there is a formula for weapons with compression cylinders, but I'm starting to think that barrel length will be a mostly cosmetic decision as it'll probably be about as accurate as it will ever be after just a few inches of pvc after the disks. Not that accuracy will be a huge concern for this weapon, I'd still like to be able to consistantly hit a paper plate from a reasonable distance.

I'll try to get some plans up on the web later tonight, when I'm not at work.

--FoamSniper
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#2 m15399

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Posted 22 March 2006 - 12:57 PM

I'm no expert on this, but as long as the disks have a good grip on the stefans, it should work. How are you going to do the barrel setup? If you have the disks spinning inside the barrel (two slots in the side that the disks sit in), then I have no idea. Probably around 6"-12". Spinning disks don't have a lot of power, so don't expect to get anything above 30 ft. Maybe if you got a kickass motor...
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#3 Forsaken angel24

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Posted 22 March 2006 - 01:21 PM

With normal foam backer rod, I am guessing you might only get 1-3 good shots with this gun per dart because the foam would break down after each shot and not be as puffy. I would suggest picking up some white foam backer rod because it is more tough when it comes to wear and tear and gets equal ranges. I am looking forward to the completion of this.


EDIT: Foam backer rods that say they are all the same diameter arent. 1/2" FBR from one company maybe thinner or thicker than 1/2" FBR from another company. So stick to one type of FBR otherwise the grip from the wheels maybe too thick or too loose.

Edited by Forsaken_angel24, 22 March 2006 - 01:30 PM.

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#4 Carbon

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Posted 22 March 2006 - 01:22 PM

For what itís worth, you pretty much have described the Nerf GyroStrike. It used spinning wheels for propulsion as well. I donít think this has ever been used in a homemade, but you can look to the Nerf version for suggestions/inspirationÖ
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#5 boltsniper

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Posted 22 March 2006 - 01:39 PM

I don`t know that you are going to be able to reall sustain full auto fire. The setup will allow full auto fire easily. But every dart that you fire will strip momentum from the wheels and slow them down. If you don`t allow time to spool the wheels back up then your range will decrease with each shot. You could minimize this problem by using high mass wheels and high speeds with powerful motors. But using wheels that are too large and heavy will produce gyroscopic forces when you move the gun around and bleed off even more energy. Probabloy happy medium in there. If you have ever messed with the motorized ballzooka then you can see this.

You won`t need a barrel that fits the darts tightly. You could probably improve accuracy by having a "barrel" that is present to jsut guide the darts. Something like 1/2" PVC for micro stefans should work well.
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#6 Jabs

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Posted 22 March 2006 - 02:04 PM

If you want some real inspiration for a design(or possibly parts to use) go pick up a Mech 6 by BuzzBee. http://www.buzzbeeto...2005/04640.html
This thing is actually gets pretty good distance stock and seems to be what you're going for. I suspect you could mod it by overclocking the motors with a higher voltage battery or by adding a hopper kinda like a paintball gun to store more than 6 darts. Good luck. -Jabs
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#7 FoamSniper

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Posted 22 March 2006 - 02:56 PM

I haven't seen the inside of the gyrostrike, but it was my assumption that that was how it worked.

My target range for this weapon is about 35 feet. The motor I plan on using actually comes from a small trolling motor (the little electric motors that you put on a bassboat so you don't scare the fish and can creep up on them), or one that I can snag from a power-wheels jeep. Either should be addeaute, weight will probably be the determining factor here.


I might pick up one of those buzzbees for parts if all else fails, I'm not interested in a topfeed design though, I've got a drum clip design that I've been wanting to build a gun suited for its use so I'd have a reason to build it.

--FoamSniper
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