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meters

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: noname » Sat Mar 31, 2007 7:41 pm

Ah, OK, much more understandable. Thanks for clearing it up.
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Unread postAuthor: ArticWolf » Sun Apr 01, 2007 2:17 am

I was told by my friends that 1.5:1 Was a good ratio but I want distance not sound. I just thought the web site I listed earlier was good to use. What would be a good ratio for distance be? If I got people confused that is what I get for listening to my friends in my town, sorry
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Unread postAuthor: SpudBlaster15 » Sun Apr 01, 2007 1:20 pm

The ideal ratio is dependent upon the potential energy within the chamber, the projectile's mass, and the dynamic friction of the projectile. For a launcher using metered propane as fuel, and potatoes as ammo, the ideal ratio is within the range of .6:1 and .7:1. For a cannon using the 'spray n' pray' method, you almost always utilize less of the energy contained within the chamber, and so a ratio of between .8:1 and .9:1 works best, if you are a master of aerosol fueling, and can achieve the best possible mixture given the inaccurate method of fueling being used. For most aerosol users, 1:1 is a good bet.
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Unread postAuthor: ArticWolf » Sun Apr 01, 2007 2:17 pm

The way I made my cannon was using metered propane/mapp, The meter pipe is 9" long and a 3/4" ID, I use 35 to 40 PSI in it at 5% of propane or mapp. The chamber is an exact 19 3/4" long at 4" ID the Barrel is 50" long and a 2" ID, all of which is all sch-40/NSF-PW, with an exact 1.50:1 C:B Ratio. A chamber fan and a 650kv stun gun for ignition. I know it is long but like I said I wanted distance. I was going to use duck tape for a burst disk to hold these little nerf balls and small plastic balls, calking tubes work to. like you said that dependent opon the chambers potential energy I thought this setup would work but any ideas can help to make it better
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Unread postAuthor: SpudBlaster15 » Sun Apr 01, 2007 3:48 pm

You could cut the barrel off about 3 inches from the chamber, and cement on 2 90 degree elbows. Using this over/under setup, you could add 2 feet of additional barrel length, and the launcher would still have the same overall length. Given your chamber size, an optimal barrel would be more than twice what you have now, but adding even a few feet would increase performance a considerable amount.
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Unread postAuthor: ArticWolf » Mon Apr 02, 2007 7:05 am

I never thought of making an over/under design. It sound's cool to try being that my cannon is not put together yet, I can still do this. So if I got you right using the over/under design can't I just cut the chamber down to 10" and if I am right the elbow's would still be considered barrel length (I could be wrong) but doing what you said and cutting the barrel down would bring me to a C:B ratio of .67:1 with a barrel length of 57" (it is still 60" long haven't cut it yet and nothing is glued together yet or drilled for that matter) wold that work? Yes I know I'm sounding like a newbie but studying is diffrent then making it. LOL
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Unread postAuthor: SpudBlaster15 » Mon Apr 02, 2007 10:18 am

The elbows would act as additional chamber volume.

Reducing the chamber volume while leaving the barrel at its current length will not increase performance a noticeable amount, and so is probably not worth doing. I suggest leaving it as it is, and extending the barrel a couple of feet. Remember, performance is almost entirely dependent on the barrel's length, should you have enough energy in the chamber to accelerate the projectile down its length.

If you intend to cut your chamber down to make the launcher more efficient and quieter, then by all means do so, as shortening the chamber will accomplish this goal.
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