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Is it true

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Is it true

Unread postAuthor: shanas91 » Sat Feb 17, 2007 7:44 am

Hi, i am new to spud gunning and my friend built a spud gun out of a 2 litre coke bottle and some thin pvc pipe. I ask him how he did his ignition and he said that he just drilled a big hole in the back sprayed 5 secs of butane then just lit a match and he said that he fire a grape out of the connon a hundred metres. Is this true i tried it my self and the bottle just melted does any one know if this is possible.

Ps: Sorry if this is a stupid question but i have seen a guy on you tube do it and i would like to no how to do it (if its possible).
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Unread postAuthor: jrrdw » Sat Feb 17, 2007 7:58 am

Normaly coke bottel cannons are pneumatic, and use a small ball valve. I can see how it caught fire and melted. As for a grape going 100 meters, i sapose anything is possible. You can search the wiki for ideas and plans there. When you get it done post some pictures so we can see.
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Unread postAuthor: big bore » Sat Feb 17, 2007 8:44 am

in the past i've tried many propellant gases for fuel, most with poor results. starting ether in the spray can from the parts house works
fairly well but the concentration is critical. MAPP gas works pretty
well because it contains acetylene. the very very best by far is
acetylene gas from a torch (gas only no air mix)
this is very powerful, my PVC golf ball gun shoots 0.6 miles.
i've had one end cap to fail slicing thru boot and foot, so use MUCH care!
acetylene gas is the miners lamp gas generated from calcium carbide
IF you can find any. my impression is it may be restricted from sale
because of possible improper use. when i tried to purchase some from
the welders supply i got the"third degree"
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Unread postAuthor: chaos » Sat Feb 17, 2007 8:47 am

big bore wrote:in the past i've tried many propellant gases for fuel, most with poor results. starting ether in the spray can from the parts house works
fairly well but the concentration is critical. MAPP gas works pretty
well because it contains acetylene. the very very best by far is
acetylene gas from a torch (gas only no air mix)
this is very powerful, my PVC golf ball gun shoots 0.6 miles.
i've had one end cap to fail slicing thru boot and foot, so use MUCH care!
acetylene gas is the miners lamp gas generated from calcium carbide
IF you can find any. my impression is it may be restricted from sale
because of possible improper use. when i tried to purchase some from
the welders supply i got the"third degree"



look i know your new mate post some pics thought it sounds sweet

peace
choas
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Unread postAuthor: boilingleadbath » Sun Feb 18, 2007 2:49 pm

No, no... MAPP does not contain acetalene.

MA - PP is:
liqified petroleum gas
methylacetylene
propadiene

The SMILES representation for methylacetylene is CC#C
Likewise, acetylene is C#C

They are not the same thing.

(propadiene is C=C=C)
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Unread postAuthor: rna_duelers » Mon Feb 19, 2007 3:58 am

5 Seconds of spray is way to much fuel,try about 1 seconds or less.Yes it does work its a very good way to pass time when its raining outside or at night.
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