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Hi. wondering if this design would work. Little hybrid

Post questions and info about hybrid (compressed gas with fuel) powered cannons here. This includes discussion about fuels, ratios, ignition systems, build types, safety, and anything else relevant.
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Unread postAuthor: MrCrowley » Fri Feb 20, 2009 6:31 pm

Rob, your drawing seems to be good enough aside from two things:

1: The burst disk. You still don't (or didn't at the time of the drawing) have any clue as to what a burst disk is, how it works or how to make one.

We've given you the information for you to look at, it is up to you to read this information and learn from it. We don't expect you to learn everything from one page on burst disks, but hopefully you will learn enough so you can search for more information on them.

Cost wise, they cost nothing. All you need is a union or cam-lock. I'd go cam-lock like starman did if I were you. The actually burst disk is made from anything, paper, tinfoil, plastic, tape. Whatever.

2: The barrel diameter. You say you want 1.75" or 2" barrel diameter. This shows me you probably don't understand PVC pipe diameters and nominal diameters.

All PVC pipe comes in nominal diameters. Since pipe has two diameters, the inside and outside diameters. The nominal diameter can be seen as 'rounding' the two diameters to a more even number. This is how you get 3/4" PVC pipe with a .67" inside diameter.

PVC pipe usually goes up in these sizes: 3/4", 1", 1 1/4", 1 1/2", 2", 3", 4", 6" etc

You can get 2.5" and a few other diameters but they are very hard to come by. Although a few hardware stores and online stores will stock some 2.5" PVC.

So when you ask for a 1.75" barrel, you can't get this diameter nominally in PVC pipe. Instead you could get 1.5" PVC SDR 21 pipe which has a ~1.69" inside diameter perfect for golfballs.

You will notice this with all kinds of pipes like 2" for example, it doesn't have an inside diameter or outside diameter that is exactly 2" inches.
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