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Pump Action Golfball Combustion

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Pump Action Golfball Combustion

Unread postAuthor: mark.f » Mon Feb 21, 2011 9:36 am

So, figured I'd post this. Planning on starting the build after my "funds" come in from my old job. I really have the money to build it now but I'm currently in school full time and don't want to put myself in any kind of financial "situation"...

So, I was awake at 2AM in bed trying to think of a way to make a high ROF repeater combustion.

The simplest idea I had was to make a pump action, where the actual "chamber" was collapsible all the way from its full volume to no volume, with a series of check valves to allow exhausting combustion gases and drawing in fresh air.

One problem, though. With a set of two check valves, in opposite orientations, the check valve used to exhaust combustion gases will also let combustion gases escape during firing, so I had to think of a way to solve this so that combustion gases were exhausted only during cycling of the operation.

What I came up with was both simple and fiddly, because there still needs to be room for a magazine and breech loader (which also acts during cycling). You can see it in the diagram below. It's just a simple check valve made from a rubber flap that sits against an immovable surface at the end of the reloading cycle. The surface area of the sealing face is much smaller than the rear of the chamber, so the "chamber" will stay sealed during firing.

Fueling is simple as well. A three-way valve propane meter is good for people who like convenience, but by using a 3-way roller valve designed for machinery, propane can be injected at the end of the reloading cycle. A check valve will have to be added after the three-way to the chamber to keep excess propane from diffusing from the meter pipe, as the chamber piston will have to rest on the three-way (leaving it constantly open).

Other stuff is kind of tricky. I wanted to make the fan collapse into a "cubbyhole" in the rear plug during reloading (the piston presses it in, and a spring pushes it back out), but this turned out to be a little too much for not much gain. The fan is recessed into the plug with space around it for airflow. Ignition will most likely be recessed into the rear plug as well. Not ideal, but it will work good enough.

Other than that, just debating whether to use a straight up-and-down magazine or one that runs along the length of the barrel. Diagram is included below. Diagram is at 72DPI and the scale is 1:1. I should have done it at 100 DPI or greater but accuracy didn't suffer too terribly... It's also not entirely complete, and a cross-sectional view doesn't lend itself too well to the front of the launcher. But it'll do for now. Any questions I can (hopefully) answer.

EDIT: inaccuracy in description.
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diagram.png
72 DPI 1:1 scale.
Not pictured: golfballs, fuel metering, electronics.
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mark.f
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Unread postAuthor: Boom_erang » Sat Mar 26, 2011 8:23 pm

Looks cool, man! Keep us updated.
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Unread postAuthor: mark.f » Sat Mar 26, 2011 8:31 pm

Don't actually know if I'm building this anytime soon or not. Spent my time mostly finishing my copper pneumatic, and I have some other ideas for future projects as well. Maybe if I feel like a combustion later.
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