Chamber to Barrel Volume Ratio Explained

[jimmy101]

hit the wrong button, see below.

[jimmy101]

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?i ... ct_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.

[dbracer443]

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.

[jimmy101]

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/).