5 gallon water bottle chamber

Eddbot · Thu Dec 13, 2007 2:01 am

ok, i was in french class the other day, and there's a water cooler with one of those 5 gallon tanks that you put in upside down, when i was getting a drink i saw the air bubbles going up into the bottle and it got me thinking.
would it be safe to use this as a chamber for combustion and/or pneumatic ? i know the mythbusters used one for a water-air rocket but i can't remember what psi they took it to

Novacastrian · Thu Dec 13, 2007 2:12 am

Defiantly good for a combustion, pneumatic yes but find out the pressure rating, i would not build a pneumo out of one. As a combustion it would be safe as banks so to speak, just don't restrict the flow with a tiny barrel, probably like a 4 inch barrel. Would be very loud.
If you make it take a pic when firing at night of the chamber, it would look awesome.

Eddbot · Thu Dec 13, 2007 2:31 am

what would a 4" barrel accomplish? isn't the flow already limited by spout-nozzle thing?

jackssmirkingrevenge · Thu Dec 13, 2007 2:35 am

Eddbot wrote:what would a 4" barrel accomplish? isn't the flow already limited by spout-nozzle thing?

Take an 'acksaw to it

the length to weight ratio is ideal for combustions but I certainly wouldn't trust it as pneumatic.

ALIHISGREAT · Thu Dec 13, 2007 2:43 am

jackssmirkingrevenge wrote:
Eddbot wrote:what would a 4" barrel accomplish? isn't the flow already limited by spout-nozzle thing?
Take an 'acksaw to it the length to weight ratio is ideal for combustions but I certainly wouldn't trust it as pneumatic.

maybe he could getto it up and wrap it in duck tape then take it to 4 000 000 psi

or you could just use it as a kick ass combustion... i have to find one of those i might get my dad to look aroud his office of something.

Killjoy · Thu Dec 13, 2007 4:17 am

Don't trust these drums for a pneumatic unless you reinforce it with say...fiber glass reinforced strapping tape. I used one of those in a pneumatic many, many years ago and it exploded between my legs, with chunks being found up to 20 feet away (though fortunantly I was not impaled).

This would be one kickass combustion though, expecially since it is clear. You could put a three inch barrel on it and shoot baseballs which would be sweet...

The Kid · Thu Dec 13, 2007 4:34 am

yeah these things are dangerous and go off at about 90 psi and when it does you sure as hell don't want to be near it.

rna_duelers · Thu Dec 13, 2007 5:33 am

I thought it was more around the 50-60 psi mark if I can remember correct that these bursted on mythbusters.

Definite combustion!

watto · Thu Dec 13, 2007 5:42 am

I'm pretty sure mythbusters burst it at 90PSI

BigGrib · Thu Dec 13, 2007 5:55 am

Killjoy wrote:This would be one kickass combustion though, expecially since it is clear. You could put a three inch barrel on it and shoot baseballs which would be sweet...

I agree whole heartedly, just one question. Is a 3" barrel a "baseball" barrel? And if so abs or pvc and what sch.

boilingleadbath · Thu Dec 13, 2007 2:21 pm

A baseball is 2.85-2.95" in diameter.

There isn't any barrel which will fit the lower end of that size range well, yet still fit the upper end of it; sch 80 PVC is 2.86, sch 40 is 3.04".

A 3" sch40 (PVC) barrel would be acceptable, I suppose, although a sabot would be a good idea.
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That said, there isn't any reason you can't use it as a pneumatic... just keep the pressure low. (I wouldn't use it above 30 psi)

A combustion may generate pretty significant pressures; I wouldn't trust this as a combustion chamber.
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Of course, I don't know the actual failure pressure of these things. Apparently, someone got one to fail at 90 psig, but that's a single datapoint...
Operating at 30 psi would give you a 3x safety margin.

jimmy101 · Thu Dec 13, 2007 5:52 pm

The bottle would probably be OK for a basic combustion, but only as a novelty.

It should handle the pressure for at least a few firings, but I wouldn't stand anywhere near it when it is ignited.

There is a video out there of a Hydrogen + oxygen fueled water rocket built from one of those bottles ...

http://www.et.byu.edu/~wheeler/benchtop/pumpkin2.php

I think I can say reliably that 11.7 bar is above the engineering specs for water-cooler bottles.

JDP12 · Thu Dec 13, 2007 6:34 pm

Yea i wouldn't trust it for a pneumatic, even if it is rated fairly high, its just not built for it.

Go with a combustion definitely, the clear chamber would look AWESOME at night.

And I don't think you should use metered propane, just stick with hairspray, cuz i believe that someone said that metered propane has the potential to reach 90 PSI.

So just stick with hairspray or something similar IMHO, maybe i'm wrong, but i wouldn't trust it at its burst limit or very close to it.

Good luck with that build let us know how it turns out.

bigbob12345 · Thu Dec 13, 2007 6:49 pm

Yea definatly do a combustion.
And I would recommend a very long 2in barel instead of a 3in or 4in you will get more power that way and just a warning on how loud and powerful this will be dont be anywhere near it when it goes off. And wear hearing protection even if you are 50 feet away( yes it will be that loud)

DYI · Thu Dec 13, 2007 7:50 pm

Considering that the chamber is more than 12" ID, and that the most efficient combustion is a single pipe of a constant diameter, he will be gaining power by increasing barrel ID, except in the unlikely situation that the barrel ID is actually greater than the ID of the chamber. And unless he has a 6" or wider barrel, he needn't worry about having a barrel too long whether it is 2, 3 or 4".

5 gallon water bottle chamber

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