Combustion Tennis Ball Cannon

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Postby acspony » Sun Dec 24, 2006 12:43 am

I did a search for this topic but didn't find the info I was looking for..

I was planning on a 2.5" x 36" barrel, and according to the 1:3 volume ratio for barrel to chamber, it looks like the chamber could be 27" x 5" diamter pipe? Is this right? The chamber seems huge... Are there other specs that use more readily available (I'd think) PVC adapters and fittings?

Thanks.
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Postby Velocity » Sun Dec 24, 2006 1:00 am

Yes, that is correct. However, combustions get maximum performance when there is a 0.8:1 Chamber to Barrel ratio. Therefore, if you are using a 2.5"x36" barrel, a 5" chamber a foot long should serve your purposes.
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Postby acspony » Sun Dec 24, 2006 1:08 am

Cool, thanks for the help.
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Postby BewareOfDog » Sun Dec 24, 2006 1:34 am

I'd like to know where you have access to 5" diameter pipe and fittings???
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Postby boilingleadbath » Sun Dec 24, 2006 8:23 am

No, combustions get maximum <i>efficiency</i> when set up with a .8:1 C:B ratio.

As untested as it is, I don't think I can suggest anything other than to run some numbers through EVBEC.
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Postby acspony » Sun Dec 24, 2006 1:38 pm

Yeah, I actually don't know where I'd find that pipe....

Does someone have plans or specs on a combustion tennis ball cannon?
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Postby Velocity » Sun Dec 24, 2006 2:12 pm

No plans, but.... for a 2.5"x36" barrel, you can use:
1) 6"x5" chamber
2) 5"x7" chamber
3) 4"x12" chamber
4) 3"x20" chamber
Looks like I did some faulty calculations when I said a 5"x12" would be an optimum chamber size... these have the best efficiency
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Postby BewareOfDog » Sun Dec 24, 2006 3:21 pm

acspony,
Spare yourself a whole lot of confusion by simply making any new combustion cannon a simple 1:1 ratio...

Some will argue that <b>0.8:1</b> is the best, others will argue that <b>0.7:1</b> is. - Some will even go so far as to say that a <b>1.5:1</b> ratio is the best.

You'll get good performance and a nice loud bang, from a 1:1 ratio. To figure <b>ANY</b> chamber size out, you must first figure out the barrels' volume.

This is accomplished by

1.)Dividing the <b>I.D.</b> (<b>I</b>nside <b>D</b>iameter) by 2

<center>2.445 / 2 = <b>1.225</b></center>

2.)Multiply this answer by itself

<center><b>1.2225</b> x <b>1.2225</b> = <b>1.49450625</b></center>

3.)Multiply <b>that</b> answer by "pi"

<center><b>1.49450625</b> x 3.14159 = <b>4.6951258899375</b></center>

This is how many cubic inches of volume you will have (per inch length) of barrel.

Round the number off to 2 or 3 digits past the decimal point:

<center><b>4.695</b></center>

And muliply that number by your intended barrel length:

<center><b>4.695 x 36" = 169.02</b></center>

With a <b>169</b> cubic inch barrel, simply do the same math for the chamber diameter, until you get to step # 3.

Then take your barrel volume of 169 and divide it by that number.
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Postby BewareOfDog » Sun Dec 24, 2006 3:43 pm

<blockquote id="quote"><font size="1" face="tahoma,verdana,arial" id="quote">quote:<hr height="1" noshade id="quote"><b>Originally posted by acspony</b>
Does someone have plans or specs on a combustion tennis ball cannon?
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

<img src="http://img.villagephotos.com/p/2003-9/398596/36inTBC.JPG">
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Postby markfh11q » Sun Dec 24, 2006 7:09 pm

Shouldn't that be a 4" spigot x 2-1/2" <B>slip</B> reducer?

Don't mean to bust your balls or anything over a minor typo, I just find it amusing whenever you mess up. [:p]
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