Page 1 of 1

Smallest barrel you can go from a 3" chamber ?

Posted: Fri Apr 30, 2010 7:34 pm
by tatfree
How small ID barrel can you go safely using a 3" chamber ( ABS material ) .

Can I go as small as 1/2" ID or even smaller ?

Using a spray and pray propane battle.


Right now I'm using a 2" chamber and going down to a 1/2 " with no issues using propane.


Thanks

Posted: Sat May 01, 2010 12:17 am
by jackssmirkingrevenge
You could probably plug the barrel without getting yourself an improvised grenade, though really for such a small barrel such a huge chamber sounds a bit overkill.

Posted: Sat May 01, 2010 12:27 am
by Gaderelguitarist
What design could you possibly be working off of to think that a 3" chamber would look good and be needed with and for a 1/2" barrel. I agree with JSR. It would be overkill
Using a spray and pray propane battle.
What for exactly? Fueling? As the Chamber itself? As a very small bench?

Posted: Tue May 04, 2010 11:57 am
by squishie
jackssmirkingrevenge wrote:for such a small barrel such a huge chamber sounds a bit overkill.
no such thing as overkill in the quest to launch various random objects in to space

Posted: Tue May 04, 2010 2:03 pm
by metalmeltr
You could go as small as you want-3/16 brake line even-but the barrel would have to be longer for optimal chamber to barrel ratio

Posted: Tue May 04, 2010 2:14 pm
by Ragnarok
squishie wrote:no such thing as overkill in the quest to launch various random objects in to space
While this attitude may be amusing at times, there is an important equation to consider:

Amusing ≠ True

Yes, sometimes overkill from the sense of "more than needed to do the job" is a good thing - but overkill also covers "so much more than needed that it's pointless and horribly wasteful".
And in this case, Jack has made a perfectly valid point - in this case, it's the latter variety. Bit like killing an ant with a hydrogen bomb, really.

Also, "launching random objects" strikes me as a good justification to build a cannon that fires dice.

Posted: Wed May 05, 2010 12:53 am
by jackssmirkingrevenge
Ragnarok wrote:Also, "launching random objects" strikes me as a good justification to build a cannon that fires dice.
Touché :)

Posted: Wed May 05, 2010 10:26 am
by squishie
Ragnarok wrote:
squishie wrote:no such thing as overkill in the quest to launch various random objects in to space
Also, "launching random objects" strikes me as a good justification to build a cannon that fires dice.
fuzzie dice or casino dice, if there fluffy mabe you could make them like the kind of pirate ship cannon ball where 2 projectiles were connected by a chain or some thing it would be quite epic

Posted: Wed May 05, 2010 4:27 pm
by Gaderelguitarist
squishie wrote:
Ragnarok wrote:
squishie wrote:no such thing as overkill in the quest to launch various random objects in to space
Also, "launching random objects" strikes me as a good justification to build a cannon that fires dice.
fuzzie dice or casino dice, if there fluffy mabe you could make them like the kind of pirate ship cannon ball where 2 projectiles were connected by a chain or some thing it would be quite epic

Facepalm

Posted: Wed May 05, 2010 9:54 pm
by Technician1002
On a more serious side, if you have an infinate size chamber (huge) there is a simple limit to the maximum flow a barrel will provide based on diameter and length. Somewhere between medium size and infinate size, the increase in size will provide very little improvement. Keep this in mind when trying to shoot the moon with overkill.

Use GGDT and HGDT to model your creations to prevent building something impractical. For a given chamber pressure, there are practical maximum limits to chamber size where going larger does not improve things any measurable amount.

For an example showing this, here is an air cannon with too large of a chamber where a chamber less than 1/2 that size will perform almost in an identical fashion. This cannon either needs a much larger valve and barrel or smaller chamber. I have a 3 gallon launcher that will outperform this launcher with a 2 inch barrel. Chronograph measurements prove it. A better valve outperforms the huge chamber. I've launched spuds in excess of 800 FPS. The larger cannon is much slower due to the valve used. His measured spud speed is under 400 FPS. He was measuring launches at 118 Meters/Second which is only 387 FPS.
http://www.crazybuilders.com/item.php?i ... ct_section

Edit; Added a screen shot of his video to show his performance is much less than predicted.