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Diesel copper gun

Post questions and info about hybrid (compressed gas with fuel) powered cannons here. This includes discussion about fuels, ratios, ignition systems, build types, safety, and anything else relevant.
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Diesel copper gun

Unread postAuthor: jmeyer1022 » Wed Jun 03, 2009 2:01 pm

I was thinking about doing it with PVC, but I don't think it could take the pressure. I got the idea after see this
http://www.youtube.com/watch?v=gLzEqfRVeOA
I'd want to go on a larger bore than bbs, Golf balls would be purty.
Not sure what I'd use for fuel either, I was thinking propane, but i don't think it would ignite. Difficulty scale on this? Suggestions? I did research on the workings of a spring powered bb gun, but I'm still unsure of how hard it will be to put this together.
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Unread postAuthor: Technician1002 » Wed Jun 03, 2009 5:52 pm

PVC compression combustion = bomb. :shock:

Not a good idea. To get combustion from combustion you need a compression ratio high enough to cause ignition. This is somewhere in the 15:1 or more ratio. 15 BAR and above in PVC is already in th danger zone. Add in ignition and the most likely result is a trip to the morgue or hospital. Copper for plumbing may fail.

Propane and other gasses heat just fine from compression. Auto ignition at high enough pressure is expected. It will most likely be explosive.

Diesel is best left to steel.
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Unread postAuthor: far_cry » Wed Jun 03, 2009 6:21 pm

and to burn i diesel you need a lot of pressure
and how you think to use diesel fuel exactly , he is like more a oil he not burn that easy
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Unread postAuthor: Lentamentalisk » Wed Jun 03, 2009 10:14 pm

Sorry far_cry, but that is completely unreadable... I think that you are saying the same thing that tech just said, but I am not sure.
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Unread postAuthor: MountainousDew » Wed Jun 03, 2009 10:25 pm

If I may try to translate...
"For diesel to ignite you need a lot of pressure, and it doesn't burn that easily because it is more like an oil.
How do you plan on using diesel exactly?"

I hope I got it right, he reminds me of myself trying to speak Spanish well. I got your back Far_Cry, or at least most of your shoulders...
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Unread postAuthor: daccel » Wed Jun 03, 2009 10:58 pm

Wouldn't diesel be a better fuel than propane because it has a lower autoignition temperature, so you wouldn't need as much compression and therefor wouldn't have as high a peak pressure? Unless that's what you're going for and building accordingly. Although I guess it requires being sprayed for best performance, which complicates things.
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Unread postAuthor: Brian the brain » Thu Jun 04, 2009 4:31 am

Best fuels would be acethylene or ether.


Ether is found in starter fluid...

Bothe have very low flash points and wide range of flamable mix
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Unread postAuthor: c11man » Thu Jun 04, 2009 7:31 am

ether is good....

my friend using the engine starter fluid (ether) in his spray and pray and it works very well.

i agree with btb on acethylene or ether. but acethylene has many disagvantages
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Unread postAuthor: jmeyer1022 » Thu Jun 04, 2009 9:29 am

I've heard to many freak accidents with acethylene. I'm going to pass under that. I'll start with starter fluid and work with other fuels if this project goes over. I was going to use copper piping, but from what I've read in responses this isn't a great idea. How high would pressures reach(I know this will vary based on the side of the gun) How high does that bb gun reach when it is dieseled?
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Unread postAuthor: jonnyboy » Thu Jun 04, 2009 12:20 pm

jmeyer1022 wrote:I've heard to many freak accidents with acethylene. I'm going to pass under that. I'll start with starter fluid and work with other fuels if this project goes over. I was going to use copper piping, but from what I've read in responses this isn't a great idea. How high would pressures reach(I know this will vary based on the side of the gun) How high does that bb gun reach when it is dieseled?

I can't tell you how fast his is going but I do know that commercial airguns when they diesel you can get an extra 300 or 400 fps. Look up dieseling an airgun on youtube. You might be able to find a regular shot vs. a diesel shot.
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mobile chernobyl wrote:I can shoot a Canuter Valve off my '82 Chevy Ram F150 AT LEAST 3/4 Mile with 'ma cannon made of soup cans duct taped together, then I just squirt some bacardi 151 in the chamber and hold up my cigarrete lighta and WHOOSH! That thing flies at least 3/4 mile
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Unread postAuthor: jeepkahn » Thu Jun 04, 2009 12:53 pm

jmeyer1022 wrote:I've heard to many freak accidents with acethylene. I'm going to pass under that. I'll start with starter fluid and work with other fuels if this project goes over. I was going to use copper piping, but from what I've read in responses this isn't a great idea. How high would pressures reach(I know this will vary based on the side of the gun) How high does that bb gun reach when it is dieseled?


there've been a few members on here that bulged their chambers by dieseling, if you can build a chamber to handle the force exerted it would make for an interesting cannon... It would prolly be considered an autoigniting hybrid....
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Autoiginition temperatures.

Unread postAuthor: Technician1002 » Thu Jun 04, 2009 1:02 pm

I found this chart that has autoignition temperatures needed for various fuels. Diesel oil autoignites at much lower temperature than propane.

LPG = Liquefied petroleum Gas. This is Propane.
CNG is compressed Natural Gas
LNG is liquefied Natural Gas
Why they have Natural Gas twice is not understood.
Natural gas either delivered compressed or liquid is still natural gas.
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Unread postAuthor: jeepkahn » Thu Jun 04, 2009 1:14 pm

And I just did some digging and for a given "chamber" diesel will produce up to 2600psi during the burn process... so just build your chamber to withstand 3000psi + and you should be fine, in fact by weight diesel will be MOAR than gunpowder as a propellant...
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