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Breech loading carburated rapid fire pump action

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Breech loading carburated rapid fire pump action

Unread postAuthor: Technician1002 » Sat Apr 25, 2009 7:17 pm

After seeing the French fry relay competition, I'm brainstorming on a rapid reload breech loading, combustion. Ignition not shown, but would probably be a pizo that strikes at the end of the loading stroke.

It's pull open to exhaust the chamber, open the breech, and draw fresh air. Pushing it closed would carburate fuel into the chamber, breech load the spud and fire. The breech plug would not blow out because of the force on the pump piston would pull it closed.

With the blue slide all the way in, it would park right at the ports into the barrel so the spud is mostly in front of the port.

The propane fuel would be delivered at 0 PSI from a bladder bag.

Think it would work?
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Pumped carburetor breech loader rapid fire spud gun
Last edited by Technician1002 on Sat Apr 25, 2009 9:23 pm, edited 1 time in total.
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Unread postAuthor: Hotwired » Sat Apr 25, 2009 7:38 pm

Slosh more colour in next time, wondered for a bit where the chamber started and ended :P

Fairly fiddly parts there such as the carburettor but should work if it follows the theory, reasonably fast reload/charge too until the heat builds up and it needs a break.

If the diagram is roughly to scale it would suggest a fairly short barrel length for that chamber size, quite stubby really. So a long tube shaped chamber along most of the barrel or a fat chamber at the base of the barrel sounds like the more likely options.

Fat chamber at the base could be more practical, shorter stroke to recharge and less surface area.

Your thoughts?
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Last edited by Hotwired on Sat Apr 25, 2009 8:07 pm, edited 1 time in total.
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Unread postAuthor: Moonbogg » Sat Apr 25, 2009 8:03 pm

I am having trouble grasping your exact vision, but I get your basic concept and I think the idea will work. My only concern that really struck me is fuel/air mixture. Having the fuel drawn in rapidly and then firing right away, the fuel will be a floating, condensed blob of gas and combustion might suck pretty bad.
Oh, cool drawing to. I like how you cropped the barrel to focus in on the important details. Maybe you could have a high speed PC fan always running like right where the gas comes through or something like that.
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Unread postAuthor: Gippeto » Sat Apr 25, 2009 8:17 pm

With a small (ish) feed line, the vacuum will be high, resulting in a higher velocity for the fuel gas.

It's momentum will help with mixing. That being said, a bit of screen or other device in the tube will add turbulence and further help even the mixture.

A fairly clever idea. :)
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Unread postAuthor: mark.f » Sat Apr 25, 2009 8:17 pm

Well, since carburetion relies on the inflow of air to draw fuel through an orifice through the slight vacuum created by moving air, you'd probably have to modify it to:

1.) Use liquid fuels if you want simplicity.
2.) Fuel on the air-intake stroke.

Just some ideas.
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Unread postAuthor: Technician1002 » Sat Apr 25, 2009 9:14 pm

Hotwired wrote:Slosh more colour in next time, wondered for a bit where the chamber started and ended :P

Fairly fiddly parts there such as the carburettor but should work if it follows the theory, reasonably fast reload/charge too until the heat builds up and it needs a break.

If the diagram is roughly to scale

Your thoughts?


The drawing was spur of the moment. I had two colored highlighters. They were mostly dry.. :(

Agreed on the heat build up. The French fry relay is 3 minutes of as much taters as you can get through a 12 X 12 cutting grid. I would hope the rate would heat it up some. :D

Diagram not to scale. Shortened severely to fit the paper. Details left out such as a handle to hold it and one to operate it. This may even work with a spud hopper for even faster rapid fire.


mark.f wrote:Well, since carburetion relies on the inflow of air to draw fuel through an orifice through the slight vacuum created by moving air, you'd probably have to modify it to:

1.) Use liquid fuels if you want simplicity.
2.) Fuel on the air-intake stroke.


A venturi works at pressure as well as air intake. Airflow creates the low pressure needed to draw fuel. Propane should work fine.

For safety, I don't want fuel/air in the front air pump. An accidental ignition there could injure the operator by shoving the piston back with considerable force.

Gippeto wrote:With a small (ish) feed line, the vacuum will be high, resulting in a higher velocity for the fuel gas.

It's momentum will help with mixing. That being said, a bit of screen or other device in the tube will add turbulence and further help even the mixture.


This high speed air through the venturi is the principal of a carburetor. It is how it draws fuel in proportion to the air flow. Feeding propane would require no screen. It would be mixed by turbulence.

Moonbogg wrote:I am having trouble grasping your exact vision, but I get your basic concept and I think the idea will work. My only concern that really struck me is fuel/air mixture. Having the fuel drawn in rapidly and then firing right away, the fuel will be a floating, condensed blob of gas and combustion might suck pretty bad.
Oh, cool drawing to. I like how you cropped the barrel to focus in on the important details. Maybe you could have a high speed PC fan always running like right where the gas comes through or something like that.


Propane, no globs. no fan needed. Mix on delivery just like the soft drink fountain at the corner gas station. No stirring necessary.
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Unread postAuthor: Gippeto » Sun Apr 26, 2009 12:28 am

I know how a carb works.
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Unread postAuthor: covey12 » Mon Apr 27, 2009 4:37 pm

i dont get it either lol
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