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Basic design for launcher

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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Unread postAuthor: niglch » Fri Aug 10, 2007 6:52 pm

Alright, I have almost all the parts I need to make the gun cut and ready for cementing (I just need to pick up some pipe clamps of the correct size). I just have one final question:

I'm assuming that the U-Bend connecting the chamber to the barrel counts as part of the chamber when calculating the C:B ratio. I did a fluid measurement the U-Bend which came out to around 720mL. My barrel is about 2332mL so I multiplied by 1.2 and subtracted the 720mL leaving me with a needed chamber volume of 2078mL. I then used RatCalc to estimate the lenght of 4" pipe I need to cut and came out with about 6.25". Sound about right for a 1.2:1 ratio?
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Unread postAuthor: Fnord » Fri Aug 10, 2007 7:13 pm

Most on here will tell you yes, you should count the u-bend/elbows as a part of the total volume, however, I think this depends on the fuel you plan on using. If you use an aerosol can of some type, the gas will probably not spread throughout the bend reliably. If you use propane with a chamber fan, it will probably equalize, but it may take a few seconds.

If you want to test this, you could inject smoke into the chamber and try to observe how it travels through the bend. Put a piece of clear tape over the hole so you can see it.
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Unread postAuthor: mike1010 » Sat Aug 18, 2007 3:20 am

what program did you use? id like to download it
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Unread postAuthor: sandman » Sat Aug 18, 2007 8:36 am

he said blender, and i use it too and its good
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