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C:B ratio

A place to ask general spud cannon related questions.
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Unread postAuthor: joannaardway » Mon Nov 13, 2006 7:28 am

That would be me that did the calculations - I thought it sounded damned familiar.

As I said there, don't use .6:1 or .7:1 - cutting a little bit off your barrel will actually increase power and muzzle velocity.

It sounded very strange to say, but that's what the maths told me.

I didn't really discover anything new (I just found extra proof of it), except what might be the ideal ratio for a fixed volume launcher - 1.25:1 or thereabouts. Not as efficent as .8:1, but perhaps more powerful.

I knew that bigger chamber increased power (with a given barrel), but I was interested to see if there was a "ceiling" to this power.
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Unread postAuthor: sgort87 » Mon Nov 13, 2006 9:27 am

Ya know, the old Latke tests tell us that isn't true that cutting off the barrel to a .8:1 is better. It shows the highest velocity for lower-friction projectiles (spuds) to be from a .6:1 ratio.
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Unread postAuthor: POS » Mon Nov 13, 2006 3:09 pm

iamthewalrus wrote:POS, the best C:B ratio for propane is .8:1, burntlake proved that, if u talking about anything other then propane idk. but for propane bigger chamber is not better.

I was talking about a pneumatic. I dont know sh*t about combustions.
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Unread postAuthor: runningawaypyro » Mon Nov 20, 2006 2:12 am

ok so this is off topic but...

for a hybrid launcher i understand the extermal metering and ignition well but not sure about the materials. i know that i should use sch80pvc but is that just for the chamber and the barrel just use normal sch40pvc? becasue you are alowing the pressure to be released donw the barrel as the projectile leaves so you would think the barrel wouldnt have to be quite as strong but i dont know. Becasue i would like to build a very large scale hybrid such as around maybr 4' 4" chanber but i i have to buy all the barrel in sch80 wont that be really expensive. i live just down the street from the keller industrial headquaters were they nationaly supply all the keller stors but its still expensive. how much does sch80pvc ushewaly run?

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