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chamber to barrel connection design

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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chamber to barrel connection design

Unread postAuthor: JDP12 » Thu Jun 09, 2011 11:38 pm

So i'm currently working on a gun, that I don't quite want to reveal yet. It's going to be based upon a video game gun, and will have a 1" barrel, and 3 1" chambers. Now via the gun design, it has a bunch of hoses. So I was thinking of connecting the 3 chambers to the barrel via some hosing, probably .5" or .75". I won't go into details of the gun design, but the drawing attached is the BASIC premise for it. so I'm worried about flow restriction. I modelled in it in HGDT as a gun with a long 1" chamber, so I'm thinking having 3 hoses around .5" ID connected to the barrel won't give that much flow restriction.

The hoses will only be around 6" or so each.. so thoughts on flow restriction?

Remember the diagram is not detailed and doesn't give a good idea of the actual gun design, just the basic chamber barrel setup.
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Unread postAuthor: hi » Thu Jun 09, 2011 11:44 pm

I dont think you will have any problems with restriction...
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Unread postAuthor: DYI » Fri Jun 10, 2011 11:41 am

Well, the three half inch hoses would only have 75% the flow of the 1" barrel, which is easy enough to model approximately in HGDT using a single chamber with the correct volume and a rupture diaphragm diameter of 0.87". Do you not have HGDT to see how that flow restriction will affect performance for yourself?

Also, are the hoses part of the chambers? You will, of course, need to make sure that the chambers are fueled very uniformly to ensure that they act as a single one, but I'm sure you've already got that sorted out.
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Unread postAuthor: Technician1002 » Fri Jun 10, 2011 12:44 pm

DYI wrote:Well, the three half inch hoses would only have 75% the flow of the 1" barrel, which is easy enough to model approximately in HGDT using a single chamber with the correct volume and a rupture diaphragm diameter of 0.87". Do you not have HGDT to see how that flow restriction will affect performance for yourself?


In reality the cross sectional area of the 3 hoses has 75% of the area, but the flow is further diminished by the extra surface providing drag to the flow. 4 1 inch pipes may have the same cross sectional area of a 2 inch pipe for example, but it won't have the same restriction to flow. This applies to valves, hoses, orifices, etc. A single large opening is much better than many small openings of the same area.

This alone is why I prefer a single large valve over two smaller valves in parallel.
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Unread postAuthor: saefroch » Fri Jun 10, 2011 3:34 pm

Technician1002 wrote:extra surface providing drag to the flow
I thought I showed that this isn't a factor with any reasonably smooth surface...

Depending on what you're shooting, you may not have to worry about flow restriction, especially if you go with the .75" hosing.

Hey! I see a stupid quote of mine made it into DYI's sig! :D
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