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Chamber to Barrel Volume Ratio Explained

A place to ask general spud cannon related questions.
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Unread postAuthor: jimmy101 » Mon May 31, 2010 11:47 am

hit the wrong button, see below.
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Last edited by jimmy101 on Mon May 31, 2010 11:50 am, edited 1 time in total.
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Unread postAuthor: jimmy101 » Mon May 31, 2010 11:49 am

Technician1002 wrote:
jimmy101 wrote: For a pneumatic it is trivially easy to calculate.
This is a common error. Calculating the valve performance at higher pressure is far from trivial. As near SOS air speeds in the valve have an impact on the maximum flow through a valve, many builders find performance in the real world is much less than trivially calculated.

This often results in barrels that reach peak velocity well before the projectile reaches the muzzle as peak flow through the valve is less than assumed.

On this page, some of the factors are mentioned.
http://www.crazybuilders.com/item.php?id=000002&type=project_section
In his videos, he shows calculated performance is quite a bit higher than measured performance.

I disagree. I said "estimate of the optimal CB for efficiency". Note the italic and underline under "estimate". Should I have used
estimate?

Besides, we are talking about efficiency (note the bold, italic underline) which has zero to do with the valve.
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Unread postAuthor: dbracer443 » Mon May 31, 2010 6:17 pm

Wow, some good conversation going on. Thanks for all the input. I really had no idea that there was this much interest or research done upon CB ratios and the more technical aspects of spud gun design.
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Unread postAuthor: jimmy101 » Tue Jun 01, 2010 7:08 pm

In case you haven't seen it, the only really decent experimental data on CB ratios was done by Burnt Latke (http://www.burntlatke.com/).
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