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Built 1st Gun, having problems

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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OK for a first gun?

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WTF? You call that a gun?
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Built 1st Gun, having problems

Unread postAuthor: wanimal » Mon Jul 02, 2007 10:18 pm

Ok, I just built my first gun, pics below. Before I added the propane today, I was using spray ether, but had problems. I would spray a half second, close the cap, and try to ignite. nothing. Then I would unthread the end-cap, waft the fumes a couple of times, and KABOOM, probably 100 yards. I was using crab apples, but they were sealing fine.

Today, I built and mounted the propane meter, as well as bevel the inside of the top of the barrel for a tighter seal. With the propane, It was firing almost every time, but going only as far as the crab apples or shorter, even though the blast seemed to be more powerful. I have a feeling that my chamber is too small, but it is the default green hornet size, as is the barrel.

every time I open the chamber I have to blow it out. should I add a chamber fan? wouldn't it melt? any suggestions?

I KNOW this thing can fly taters farther, just help me out here.

<a href="http://photobucket.com" target="_blank"><img src="http://i159.photobucket.com/albums/t159/wayfan1990/PotatoCannon2.jpg" border="0" alt="Photo Sharing and Video Hosting at Photobucket"></a>

<a href="http://photobucket.com" target="_blank"><img src="http://i159.photobucket.com/albums/t159/wayfan1990/PotatoCannon1.jpg" border="0" alt="Photo Sharing and Video Hosting at Photobucket"></a>

<a href="http://photobucket.com" target="_blank"><img src="http://i159.photobucket.com/albums/t159/wayfan1990/PotatoCannon3.jpg" border="0" alt="Photo Sharing and Video Hosting at Photobucket"></a>
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Unread postAuthor: Specialist » Mon Jul 02, 2007 10:28 pm

it looks great for a first. yeah, i would add a chamber fan. and no combustion blasts are like 50ms so no it would only get warm. you may have slight melting if you dont give like 10 seconds between each shot. the chamber doesnt look too small it could be bigger and that would boost performance but it looks ok. as for your problem with using spray try holding it for atleast 4 seconds. you where just probably not putting enough in thats all. i know that wont help if you get the propane working the way you want ti to but if your not using it try what i said and it will probably work. again, nice gun and great first.
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Unread postAuthor: hi » Mon Jul 02, 2007 10:40 pm

very nice first.

here is a good thing to go by:

if the sparker works, the cannon works. you just have to keep trying until you get it to work.
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Unread postAuthor: wanimal » Mon Jul 02, 2007 11:15 pm

i know, i just think the C:B ratio is outta whack
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Unread postAuthor: TwitchTheAussie » Tue Jul 03, 2007 12:37 am

hi wrote:here is a good thing to go by:

if the sparker works, the cannon works. you just have to keep trying until you get it to work.


Not true mate mine isnt working but as for yours mate just add some more fuel or upgrade your fuel and/or mix it with others. You could try adding a spark strip if you want.
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Unread postAuthor: frankrede » Tue Jul 03, 2007 12:47 am

I see a girl in the backgorund;)
not bad for a first gun, better than mine.
Definetly add a fan, it helps so much
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Unread postAuthor: wanimal » Tue Jul 03, 2007 6:42 am

lol, that girl is my sister.
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Unread postAuthor: spud yeti » Tue Jul 03, 2007 6:51 am

I prefer the girl to the cannon... more pics please!? LOL, great looking cannon though! Id just add the chamber fan.
btw, how old is she?
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really good quote/phrase here
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Unread postAuthor: chaos » Tue Jul 03, 2007 7:26 am

spud yeti wrote:I prefer the girl to the cannon... more pics please!? LOL, great looking cannon though! Id just add the chamber fan.
btw, how old is she?


yer im with you mate girl over the gun.....unless shes holding the gun Oh! get a pic of that!!
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Unread postAuthor: MrCrowley » Tue Jul 03, 2007 7:47 am

Bad move getting your sis in the pic on a international forum that is probably 99% male.

Nice first cannon btw.
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Unread postAuthor: paaiyan » Tue Jul 03, 2007 7:59 am

Yea, I definitely think a chamber fan would help a lot, some of your power deficiencies may arise from leftover CO2 after each shot. Also, play around with the amount of propane you inject, you could be putting in too much or too little. It is a nice looking cannon though. And I see a bottle of Coke on the floor... Me thirsty...
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Unread postAuthor: spud yeti » Tue Jul 03, 2007 8:02 am

Does the fan just mix the gases and then clear the chamber?
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really good quote/phrase here
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Unread postAuthor: paaiyan » Tue Jul 03, 2007 8:06 am

For the Coke. The fan helps aid in the diffusion of the gasses to begin with in order to make the combustion faster and cleaner, and it helps to clear the CO2 after each shot.

Merged:

So in conclusion wanimal, try to get a chamber fan, check the fuel/air mix, and try not to include your sister in pics, lol.
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Unread postAuthor: psycix » Tue Jul 03, 2007 8:34 am

A fan will indeed boost the prestations and you might want to check your mix like he said.

Also: Do your potatoes make a tight fit? No air may slip through when spud is in barrel.
Maybe get a larger potato then and cut a perfect fitting cillinder out of it with a muzzle knife.

Whats the ratio of the gun? Also please give the chamber/barrel sizes.\


ps: You may include sister in pics, we dont mind... :P
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Unread postAuthor: SnowFlox » Tue Jul 03, 2007 11:00 am

nice cannon ! but about the tank.

when you hold it horizontal.. doesnt it gives liquid instead of gas ?
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