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Post by Jmes Kelly on Jun 4, 2005 14:18:03 GMT
I'm about to construct a new cannon that is much bigger than the one on the main site but im slightly worried about how robust (how thick i need to make the 'walls' of the cannon) to make it. has any one constructed a large combustion potato cannon?? I'd like some advise/info cheers  |
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Post by exuz on Jun 12, 2005 22:11:19 GMT
tried to build one once, but couldn't get the ignition to fire  but we used roadside sign pole, wich are 4-5 mm thick steel, as combustion chambre, and a thinner sign pole as barrel. the thing got pretty heavy, but it would withstand rather heavy fireing,, if we could work out det ignitor that is. sorry for my bad english |
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Post by James Kelly on Jun 13, 2005 11:42:33 GMT
Well if ur cannon was only a relitivly small cannon you should just be able to use pvc tubing rather than thick steel piping which is more expencive, heavier and harder to add fittings to as you would have to weld them together or sumthing.
What sparker/igniter were you using, it may have got earthed on the sides of the metal cannon, or it may have not been a strong enough spark, or you may not have got the correct fuel to air ratios right.
like to know more about the size and type of your cannon.
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Post by James Kelly on Jul 25, 2005 15:19:55 GMT
I've completed the cannon now - its huge! (3.5m ish)
I'm leaving it to 'dry' so that all the weldings can cure properly - i don't want it to explode!
Testing of the cannon should comence within a fortnight, then i will start toupload the plans and details on how i made it on the main website.
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Post by James Kelly on Sept 24, 2005 12:12:29 GMT
Ive fire the cannon dozens of time now and have not had any problems (other than trying to carry the giant arround with a friend). It is really power full one of the first fireings, i stupidly left the loading pole in the barrel and fired - good bye loading pole!!!! and the cannon's recoil was rether big too!  I am testing various projectiles to fire from the cannon as potatoes seem to get obliterated when fired - i was thinking of golf balls (with potato ram), snooker balls and ice blocks. As i have finished the main testing of the cannon i will write up and upload the project details soon.  Visit soon to find the latest updates. |
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Post by James Kelly on Jan 21, 2006 2:16:07 GMT
At last this project is up on the site! If youve made a small cannon i suggest you make a big one now! they are really really fun!!! ... oh and the other projects are coming - im re-writing them, and then they can be uploaded. |
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Post by joshua wainwright on Mar 9, 2007 23:00:19 GMT
is there a general ratio for the volume of the barrel in proportion to the volume of the chamber, for-maximum efficiency?
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Post by James Kelly on Mar 10, 2007 13:24:57 GMT
When i was designing my big cannon the ratio of barrel to chamber volume was an important and rather vague problem to sort out. It depends on the size of your cannon and the propellant used. I found that i had to talk to more advanced spudders who had delt with large cannons a lot - they sugguesed that the best ratio for my big (3.65m) cannon was 0.8:1 barrel to chamber volume ratio to be the most efficient using propane as a propellant. However the most popular ratio for smaller cannons was 1:1.5 barrel to chamber ratio. The more efficent ratio (0.8:1) gives a quite but powerful fireing whereas the less efficient ratio (1:1.5) gives a much loader fireing but supposedly lower power/range. I would suggest to talk to the same group of people i talked to during my design stages at the forum at this site: www.spudtech.com/Or a betterway would be to experiment with different ratios for the size of cannon ou building and make your own conclusions to what gives the best performance. Hope this helps you on your way. |
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