why isn't an extension combusion chamber working

Post questions and info about combustion (flammable vapor) powered launchers here. This includes discussion about fuels, ratios, ignition systems and anything else relevant to launchers powered by igniting things like hairspray or propane.

Postby brogdenlaxmiddie » Mon Nov 27, 2006 11:28 am

i added and extension chamber for the explosive components to do its thing... i double the load and yet it shoots no more than the origanal load of hairspray... why is it doing that... please resond or email me.. thanks
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Postby Freefall » Mon Nov 27, 2006 2:26 pm

Did you make your barrel longer too? The chamber makes the power, the barrel puts that power into the spud. Unless you made your barrel longer, you're not going to get much extra performance from a bigger chamber.
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Postby SpudStuff » Mon Nov 27, 2006 6:35 pm

I think the problem isn't the gun but rather the fuel. You could have had a good mix down before and with the new chamber you have a bad mix.
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Postby Mr.Plow » Mon Nov 27, 2006 7:35 pm

I'm not so sure, spudstuff. I support Freefall's explanation. Simply put, after you've passed the ideal ratio you're not going to notice significant range increases. You've got to lengthen your barrel accordingly.
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Postby sgort87 » Tue Nov 28, 2006 1:27 am

I'm fairly certain both are correct. The barrel being short is a problem, but it is very much harder to get the correct mixture in a longer chamber.

I would try adding a fan inside your chamber to mix the fuel. You should notice a big difference.
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Postby aturner » Tue Nov 28, 2006 2:04 pm

Could cross sectional density be an issue here?

Let's suppose we can achieve higher muzzle velocities by increasing the barrel length (or by any other method). How much of a velocity increase are we talking about? Now, with the same sized projectile (and same cross sectional density), will the <i>distance</i> be substantially different? Shouldn't we expect to see diminishing returns?
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Postby boilingleadbath » Tue Nov 28, 2006 4:20 pm

Aturner, there are deminishing returns on both fronts; a larger chamber doesn't give you the extra preformance you'd expect, and that extra muzzle energy doesn't give you the increase in range you might expect.

If one ignores the effect burn time has on the muzzle energy, EVBEC is probably acceptable for <i>estimating</i> muzzle energy, and the GGDT's ballistics tool seems to be the only accurate thing running anymore.
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