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| fastcannonman |
 Posted: 05/31/2007 9:37 AM Post subject: small combustion cannon |
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Corporal
Joined: 30 May 2007
Posts: 72
12.87 Spud Bux
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idems you need
1 pill bottle
2 small nails
1 bbq igniter
1 pen tube
5 inch speaker wire
1 roll electric tape
a pen sized drill bit
a drill
super glue
qtips
Instructions
1. Drill a hole on the bottom of the pill bottle.
2. Stick a pen tube in the hole and seal using super glue.
3. Stick the nails in the side of the pill bottle opisit of eachother, leaving a quarter inch space between them.
4. Split some of the speaker wire about 2 inches and tie one wire to one nail and the other wire to the other nail.
5. Connect the two wires from the bbq igniter to the two remaining speaker wires.
6. Tape the bbq igniter to the pill bottle.
7. Open the pill bottle, look in it and test the igniter.
8. If it works then you finished, if not try putting the nails closer tigahter.
To fire
1. Put a qtip in the pen tube.
2. Then open the bottle and spray a LITTLE propellent in the bottle.
3. Press the igniter and boom, it should have shot the q tip across the room.
picture are comeing soon! i am uploading them now |
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| fastcannonman |
| Posted: 05/31/2007 10:50 AM Post subject: |
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Corporal
Joined: 30 May 2007
Posts: 72
12.87 Spud Bux
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| does anyone have any tips on how i can profect this cannon |
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| garfield |
| Posted: 05/31/2007 11:14 AM Post subject: |
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Private
Joined: 15 Feb 2007
Posts: 15
0.50 Spud Bux
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| ive made one of these befor. but it backs up very quickly, and blows the end cap of =/ overal nice job! |
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| jimmy101 |
| Posted: 05/31/2007 12:59 PM Post subject: |
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Major General
Joined: 28 Mar 2007
Posts: 1567
6648.31 Spud Bux
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Not a lot of optimization that can be done on a gun this small but you might consider: (This would be a great science fair project)
Chamber fans are usually a big help in combustion guns, but won't fit in a pill bottle. Might try dropping a couple BB's (or something a little larger) in the chamber. Shake the chamber to get the BBs to help mix the gases.
Replace whatever you are using for fuel with either a disposable butane lighter or a propane tank and use a cheap syringe to accurately meter the fuel. Like this or this. The gun will perform much better, both more powerful and more consistent, if you accurately measure the fuel. For a mini, you will need a fairly small syringe, perhaps a 5cc or 10cc disposable. You can usually get them at places that sell livestock supplies. Should cost less than $1.
Try to properly size the barrel volume to the chamber volume. I suspect the volume of your chamber is probably much bigger than the volume of the barrel. The performance of a 10:1 chamber to barrel is going to suck. Perhaps change the barrel to 1/4" copper tubing so you can use a much longer barrel. BBs fit in 1/4 copper tubing pretty well, a small piece of tissue paper can be used as a wading. Spuds work also. Not sure how well Q-tips fit in 1/4" copper tubing. |
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| jackssmirkingrevenge |
| Posted: 05/31/2007 13:12 PM Post subject: |
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space monkey
Joined: 15 Mar 2007
Posts: 6485
9880.03 Spud Bux
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| jimmy101 wrote: | | Chamber fans are usually a big help in combustion guns, but won't fit in a pill bottle. Might try dropping a couple BB's (or something a little larger) in the chamber. Shake the chamber to get the BBs to help mix the gases. |
You could make a small fan out of aluminium from a pop can and attach it to a shaft that projects out of the bottle and have it powered by an external source. |
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| boilingleadbath |
| Posted: 05/31/2007 19:51 PM Post subject: |
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Moderator
Joined: 12 Mar 2005
Posts: 1647
5491.22 Spud Bux
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"The performance of a 10:1 cannon will suck"
Not from a energy/barrel length perspective, which (for guns optimized for overall length) is is pretty close to the point.
My reasoning is that:
A) A mini is small, so the fast combustion approximation applies.
B) Under the fast combustion approximation, larger chambers mean less pressure drop over the cycle, which means higher average pressures.
C) Higher average pressure equals higher velocity. |
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| Will-91 |
| Posted: 05/31/2007 21:39 PM Post subject: |
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Private
Joined: 31 May 2007
Posts: 4
7.70 Spud Bux
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| Whats the best propellent? |
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| fastcannonman |
| Posted: 05/31/2007 21:41 PM Post subject: |
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Corporal
Joined: 30 May 2007
Posts: 72
12.87 Spud Bux
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| i find axe works well. red zone works two |
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| Will-91 |
| Posted: 05/31/2007 21:45 PM Post subject: |
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Private
Joined: 31 May 2007
Posts: 4
7.70 Spud Bux
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| OK, cool. Thanks for that. |
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| Will-91 |
| Posted: 05/31/2007 22:09 PM Post subject: |
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Private
Joined: 31 May 2007
Posts: 4
7.70 Spud Bux
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| I cant get it to shoot. The propellent wont light. what should I do? |
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| fastcannonman |
| Posted: 05/31/2007 22:13 PM Post subject: |
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Corporal
Joined: 30 May 2007
Posts: 72
12.87 Spud Bux
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| i would try using less proplent. open the cap and click the igniter. do u see a blue line inbetween the nails? |
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| keep_it_real |
| Posted: 05/31/2007 22:13 PM Post subject: |
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Captain
Joined: 23 Dec 2006
Posts: 306
448.75 Spud Bux
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| Probably use less fuel. Make sure the chamber is well ventilated. A chamber fan would also help. |
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| gotbass7 |
| Posted: 05/31/2007 22:16 PM Post subject: |
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2nd Lieutenant
Joined: 02 Feb 2007
Posts: 213
52.30 Spud Bux
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| this is important. shake the gun and blow in the chamber. try spraying really really fast. once. on bigger guns, spray really really fast a couple times |
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| fastcannonman |
| Posted: 05/31/2007 22:31 PM Post subject: |
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Corporal
Joined: 30 May 2007
Posts: 72
12.87 Spud Bux
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| jimmy101 wrote: | | Might try dropping a couple BB's (or something a little larger) in the chamber. Shake the chamber to get the BBs to help mix the gases. |
try that
Merged:
tell me when u get it to work and if u need more help pm me
Mod Note: I swear to god fastcannonman if you don't learn the rules and posting procedures soon your looking at a post ban. |
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| hi |
| Posted: 05/31/2007 22:33 PM Post subject: |
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Major General
Joined: 01 Feb 2007
Posts: 1451
1004.40 Spud Bux
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| i find that ( on really mini mini mini cannons) that you spray it, then wave it in the air back and forth for about a second, then cap it and shoot it. it works every time. |
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