SpudFiles

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Well, after a fair bit of work I decided on how to finish the gun. It would have a replaceable, bolted (with screws) plug. 6 Plugs cracked later I decided to give up. It was riddled with irritating problems, most of all the fan and strip taking up far too much space.

Today I did a complete overhaul on the design, changing nearly everything. A schrader valve has been added, potential for a burst disk, better aesthetics, more space in the chamber, better metering, more reinforcement and easier access. If I can lay my hands on the parts it will also include a fan timer. Barrels will thread into a 1/4" female thread. With this I'm also designing over sized barrels for a "mortar" and thread on mini grenades (spigot mortar).

The design was drawn up on paper last night, then put into motion this morning. Currently the paint on the chamber is drying. The design was originally drawn up on paper, and I'm about to re-draw it in paint.

Stay tuned for updates

Well I had primed it, painted it and decided to put a clear coat on. Big mistake. All the paint melted and everything got deformed, so I started again without paint.

Specs:
Schrader for purging/hybrid capabilities.
Reinforced with aluminium angle.
4 gap spark strip, perspex and copper tape. Screwed into chamber. 1/4" threaded female fitting for barrel attachment.
Mini piezo for portability. Can be hooked up to any other source eg. stungun.
Metered butane injected directly into chamber. 12 Ml syringe used for measure.
High RPM 3 blade fan. Uses a dip switch (basically a tiny on/off switch) to conserve space.
1/2" Chamber

Wow how very not-ghetto compared to most mini's. Clean build, good job!

were would i get a fan like that?nice mini combustion to.

Is that a "brushed" motor driving the fan? If so, not a good choice. Other wise nice build.

Brushed motors are indeed not recommended. Though I don't think this mini would do alot of damage if it went of accidental.

Do brushed motors create sparks? You can imagine why that would be bad in a combustion. You wouldn't even need the piezo just turn the motor on. Is that a flare fitting?

A brushed motor has a chance to spark. PC fans are brushless.
The fuel mix should be able to reach the spark in order to ignite so people have successfully used brushed motors after sealing off the cooling vents with hot glue.

Yes, the motor is brushed. I considered this, but decided that it was sealed well enough that if I kept the endbell out of the chamber, it would be fine. The end plug is simply a piece of coupler, with perspex epoxied into the end.

The fan is adapted from the motor out of a mini crazy remote control car (basically a pager motor, but a much higher rpm.) And a 3 bladed stabilizer fan from a toy helicopter, cut down to fit the pipe. It's mounted conveniently in the hole the holesaw makes while cutting out the perspex.

Fan electrics have been added, a push button switch with two piggy back mini rechargeable batteries and an LED. The batteries are rechargeable through my RC peak detection charger, which is good. I also finished up the fueling system, and decided to give it a quick test. WTF!! there were no cigarette lighters at all! no butane, propane, anything. Not even mapp!
So testing is halted till I can go down the store and buy a cigarette lighter for fuel..

Well, I grabbed the good camera today and got some better pics (sorry 56k guys..)













There we are

Well nice! Pick up that fuel and show us how it shoots!

I love it.

Strap the lighter permanently to the gun and hook your little piece of tubing to it ... on board fuel supply.

You might as well just use "one-potato two-potato ..." timing for fueling directly from the lighter. Lighters supply fuel pretty slowly (and they can be adjusted to get a conveint fueling time) so even with a small chamber it'll take a second or two to fuel.