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Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
A picture is worth 1k words:
Pour a bit of ethanol into the film case (is this the right word?), and pour it back so just a little of it got stuck on the walls. Put the film case on the lid that is glued to the base. There is a small spark gap in the lid, and when you press the FIRE button, a spark jumps in this spark gap and ignites ethanol vapors that have developed inside the film case and BANG it flies high in the air. I don't know why is that when I repeat it quickly, it doesn't do anything, I need to clean the inside of the case from the remainings of the ethnol, then it works again.
Registered Member #95
Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308
Lol, I made one of those a long time ago too. I just used a piezo ignitor to fire it, worked great. Blow fresh air into the film can after each fire, it should work every time then. Certain types of hair spray will work for fuel as well.
Geometrically Frustrated Registered Member #6
Joined: Thu Feb 02 2006, 04:18AM
Location: Bowdoin, Maine
Posts: 373
Neat little project. How high does it send the film canister?
jmartis wrote ... I don't know why is that when I repeat it quickly, it doesn't do anything, I need to clean the inside of the case from the remainings of the ethnol, then it works again.
Is that actually because of residue on the inside, or is there just co2 in there?
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
With buthane it can reach 10 meters or so. Hydrogen and oxygen can give quite nice results and can burst the container.
Some fuels are quite sensitive to the mixture ratio so it is possible that it will not ignite the second time because there are fuel remains on a large area that evaporates quickly and makes the mixture too rich.
If you have some water in the container you will get higher speeds and everything will get wet.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Alex wrote ...
Neat little project. How high does it send the film canister?
I think about 10 meters, but it makes a nice loud BANG
Today it was firing unreliably (about 2 succesful shots of 10 tries) so I added a small HV cap on the output of the (rectified) flyback, now it makes nice juicy spark and fires more reliably. (however I thing such fat spark shouldn't be requied when people succesfully use piezo lighter?)
Registered Member #33
Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971
I've made many of those. Most of them were based on piezo igniters from lighters, but one of them used a disposable camera inverter and a 5 stage C/W-cascade to make a 6mm long spark for ignition. Memories...
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Film canister cannon
