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| jon_89 |
 Posted: 06/26/2007 14:14 PM Post subject: more power |
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Lieutenant Colonel
Joined: 11 Apr 2007
Posts: 429
568.78 Spud Bux
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| i have a 1.5 by 3.5 inch chamber and am currently using propand. is there any way to get more power? |
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| hi |
| Posted: 06/26/2007 14:26 PM Post subject: |
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Major General
Joined: 01 Feb 2007
Posts: 1456
1019.01 Spud Bux
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as soon as you describe what propad is. just kidding.
mapp gas is slightly more powerful. |
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| jon_89 |
| Posted: 06/26/2007 14:31 PM Post subject: |
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Lieutenant Colonel
Joined: 11 Apr 2007
Posts: 429
568.78 Spud Bux
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| oops! will another spark gap give it more power? |
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| hi |
| Posted: 06/26/2007 14:37 PM Post subject: |
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Major General
Joined: 01 Feb 2007
Posts: 1456
1019.01 Spud Bux
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| it might, but its so small you wont even notice, it may be worth a try if you are bored enough. you really cant expect much out of a cannon that small. |
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| Spudgun on Crack |
| Posted: 06/27/2007 19:34 PM Post subject: |
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Corporal
Joined: 23 Jun 2007
Posts: 79
322.13 Spud Bux
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YES YES I CAN GET YOU MORE POWER!!!!!!
TRY AT YOUR OWN RISK!!!!!
This is dangerous but the power will be very very powerful.
Ok so you are using propane right, now go to the store and go to the blow torch isle and get the oxygen cylinder. Now mix a little oxygen and propane/mapp gas in the chamber and the force of the combustion may blow off the cap or explode the chamber so you may do this at your own risk!
This will get the most power! |
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| Arborman |
| Posted: 06/27/2007 19:39 PM Post subject: |
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Specialist
Joined: 16 Mar 2007
Posts: 51
5.81 Spud Bux
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oxy enriched mixes and non metal chambers dont go well together.
Enrich and DIE!!
im assuming you have a plastic chamber... |
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| VH_man |
| Posted: 06/27/2007 19:56 PM Post subject: |
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Major General
Joined: 09 Dec 2006
Posts: 1333
1952.11 Spud Bux
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spekaing of more power, this would have to be with metal chambers........
has anyone made a combustion powered by white gas?
i treid it once in my PVC combustion (BAD IDEAAAAAAA!!!!!!!!) and i amazingly didnt die/get infused with PVC particles. however, the spud went FAR!!!!!!! it was amazing.
just a thought........ dont try it........ unless you have metal as your chamber |
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| turbohacker |
| Posted: 06/27/2007 20:21 PM Post subject: |
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Major
Joined: 20 Dec 2006
Posts: 393
487.48 Spud Bux
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Has anyone experemented with liquid fuels injected through little misters?
Im thinking some oxygen and liquid nitro-methane  |
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| VH_man |
| Posted: 06/28/2007 20:54 PM Post subject: |
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Major General
Joined: 09 Dec 2006
Posts: 1333
1952.11 Spud Bux
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lol. thats a good idea. better than sitting there for 5 minutes waiting for gasoline to evaporate............
bah if only i was allowed to make combustions. id have a Gas-powered marlbe sniper by now......... |
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| Spudgun on Crack |
| Posted: 06/28/2007 22:07 PM Post subject: |
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Corporal
Joined: 23 Jun 2007
Posts: 79
322.13 Spud Bux
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I think that a 3/4inch to 1/2 inch all copper mini will be able to have and oxy rich fuel.
I am off to build one and i will make a topic about this as it does not take that much effort on my part to get a 3/4 in to 1/2in reducer a female adapter for the fuel injection cap in the back.. and a little bit of 3/4in and 1/2in pipe |
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| Flying_Salt |
| Posted: 06/28/2007 22:24 PM Post subject: |
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Post whored my way up
Joined: 09 Oct 2006
Posts: 785
136.98 Spud Bux
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Don't enrich it with a pvc chamber. It will explode. MAPP gas is slightly stronger than propane. Do you have a chamber fan? Those help mix the fuel, even though your chamber is so small it won't change much. Multiple spark gaps can improve preformance slightly but you probaly wouldn't notice.
The best way to improve power would be an insanely thick and strong steel chamber with an oxy/acetylene mix. |
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| jimmy101 |
| Posted: 06/29/2007 12:28 PM Post subject: |
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Major General
Joined: 28 Mar 2007
Posts: 1594
6760.52 Spud Bux
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| VH_man wrote: | spekaing of more power, this would have to be with metal chambers........
has anyone made a combustion powered by white gas?
i treid it once in my PVC combustion (BAD IDEAAAAAAA!!!!!!!!) and i amazingly didnt die/get infused with PVC particles. however, the spud went FAR!!!!!!! it was amazing.
just a thought........ dont try it........ unless you have metal as your chamber |
You are doing something wrong if gasoline gave significantly more power than other fuels.
The fuel content, per mole of oxygen required, for gasoline (white or red) is essentially identical to propane. IIRC, the difference in energy is ~1%.
All most all hydrocarbon fuels contain basically the same amount of energy per unit of available oxygen used in the combustion process. The only real outlier is acetylene which has ~15% more energy per mole oxygen than does propane. (Hydrogen is also an outlier at ~15% more energy but hydrogen isn't a hydrocarbon.) |
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| jimmy101 |
| Posted: 06/29/2007 12:39 PM Post subject: Re: more power |
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Major General
Joined: 28 Mar 2007
Posts: 1594
6760.52 Spud Bux
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| jon_89 wrote: | | i have a 1.5 by 3.5 inch chamber and am currently using propand. is there any way to get more power? |
First of all what are the other dimensions of the gun and what are your projectiles?
Minis tend to have barrels that are much too small for the chamber volume.
Your chamber is 6.2in3. If you are using 1/4" copper tubing for the barrel it needs to be ~10 feet long for a CB of 1.0. It will probably perform OK with a 5~7 foot barrel (CB 2~1.5).
For 1/2" tubing the barrel would need to be 2.5 feet long for a CB of 1.
The other thing that might help would be a chamber fan. If you can fiind a small enough dc motor you can make your own. The tiny vibrator motor used in cell phones works well. |
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| jon_89 |
| Posted: 06/29/2007 20:14 PM Post subject: |
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Lieutenant Colonel
Joined: 11 Apr 2007
Posts: 429
568.78 Spud Bux
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| .5 by 18in and i am using either potato or paper darts with a screw for weight |
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| jimmy101 |
| Posted: 06/30/2007 11:56 AM Post subject: |
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Major General
Joined: 28 Mar 2007
Posts: 1594
6760.52 Spud Bux
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So your CB is about 1.7. A little on the high side but to get a better ratio the barrel would have to be a lot (~2x) longer. And even then the increase in performance isn't going to be a whole lot.
I would think you best chances at improving the performance are;
1. Figure out how to add a chamber fan (hard to do, need a really small motor). Better mixing helps performance and having moving gases during combustion may speed up the burn rate.
2. Try to increase the static friction (particularly with the paper darts). With PVC barrels people increase the static friction by double beveling the muzzle knife so the spud is cut a bit oversize and fits very tightly in the barrel. Combustion guns seem to prefer a fairly high static friction between the ammo and barrel, acts kind of like a burst disk. If your barrel is PVC then double bevel the muzzle. If your barrel is copper I can't think of anyway to get a double bevel to work since the barrel wall is so thin.
Edit:
Sorry, I probably should describe what a "double bevel" is. Normally, you sharpen the end of the barrel (by fileing, sanding, ...) so the muzzle is sharp like a knife. When you shove a whole spud down on the muzzle the sharpened end of the barrel slices through the spud cutting it to exactly the size of the barrel. A double bevel knife means you file down both the outside and the inside of the muzzle. The resulting circular knife edge has a diameter a bit greater than the barrels ID. When you shove a spud down onto this type of cutter the spud is cut large and then compressed down to the barrel ID. For a 2" barrel you can easily get 30 pounds or more of static friction using this method. |
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