need some advice

[sgehring]

I have built some air powered cannons and one very basic combustion. I was checking my stockpile of parts and pieces and I should have everything I need to make an "advanced" combustion". I have looked over Pete Zaria's design and gleaned some ideas from that as well as Gort's Blue Flame. I have some ideas to make my "own" style gun, Here are what I hope are not too stupid of questions. I have been reading in the posts and the wiki that the ideal combustion chamber ratio is .8/1. To make the math easy if I had a 80cui chamber would I want a 100 cui barrel? When you are measureing the "chamber" I assume you measure everything right up to the back of the projectile, in this case golf balls, is this correct? The wiki talks about the ideal ratio being the most fuel efficient as well as quiet. Propane is cheap and noise is not a factor where I will be using he gun. I want power and lots of it. My air guns will launch a golf ball clear out of sight. Can I get 300 yards, with a golf ball and propane metering in a gun I shoot by holding on to it or do I need to make a "cannon" to get that kind of distance. I have 10 feet of 4" sch 40 and at least 60 feet of 2" sch 40 and 80 feet of sdr21 and scraps of everything in between. So I can built a huge cannon but I already have a huge air cannon now. For discussion sake if I used a 24" X 4" chamber with elbows and such I figure I will have a chamber volume of about 340 cui, if I include in the elbows etc. prior to the projectile. With a 6 foot golf ball barrel how far could I exspect to get? If I can't get the distance I will may put my time and money into another air powered gun. Though it always interesting to do something different.

[Insomniac]

Well, seeing as you can get fuel cheaply, and noise isn't a problem, I would advise that you work out what barrel length that you want, then over-chamber it. That way it will be able to run on less powerful fuel and still have a good C:B ratio, and the gun will be louder and have more muzzel flash. Even though that won't affect performance, it will make the gun 'feel' more powerful, and then if you make it have interchangerble barrels you will have more flexibility with the lengths the chamber will be suitable for.

[sgehring]

it will defeinatly have interchangable barrels. That way I can use use the ones from my air cannons, 4ft and 6 ft, and a 20foot golf ball barrel I am putting together to use on all the guns. I refill my "throw away" propane bottles from a bigger tank and I figure it costs well under a $1 to refill one.

[sgort87]

The optimum ratio for best performance is actually .6:1 for spuds and most other projectiles.

[newkidspudster]

Good luck making your cannon,it sounds like a good idea.