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Propane leaving barrel

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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Unread postAuthor: Crna Legija » Sun Oct 07, 2012 5:12 am

try put a internal chamfer on the barrel barrel so you cut over size spuds that fit the bore tighter.
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Unread postAuthor: ninjamonkey127 » Sun Oct 07, 2012 5:51 pm

Crna Legija wrote:try put a internal chamfer on the barrel barrel so you cut over size spuds that fit the bore tighter.

I don't understand.
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Unread postAuthor: jsefcik » Sun Oct 07, 2012 9:25 pm

MrCrowley wrote:
jsefcik wrote:i wouldnt leave the fan on, just put it on for a couple seconds
...and you continue to show just how much you don't know. Leave the fan on, I believe it increases turbulence and results in a faster combustion. Someone more knowledgeable on the subject can correct me if my justification is wrong but it seems to be pretty common practice nowadays to leave the fan on during combustion.



ive had better performance turning it off,i left it on and performance wasnt as good, and i do know, saying you believe is just the same as me thanks

what ever works best roll with that
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Unread postAuthor: Crna Legija » Mon Oct 08, 2012 4:52 am

ninjamonkey127 wrote:I don't understand.


:roll:
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Unread postAuthor: ninjamonkey127 » Mon Oct 08, 2012 7:57 am

Crna Legija wrote:
ninjamonkey127 wrote:I don't understand.


:roll:

Oh, now i see. I'm gonna give this a try.
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Unread postAuthor: jrrdw » Mon Oct 08, 2012 9:56 am

Having a chamber fan you should be loading the potato before fueling or you fuel mixture will be in the barrel. Hope I didn't misread or repeat anyone it's hard not to with the long quotes on the 1st page.

Are you getting consistant firing yet?
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Unread postAuthor: ninjamonkey127 » Mon Oct 08, 2012 4:51 pm

Thank you Crna Legija for the advice! It definitely worked. But now i have a broken fan and i think i have a leak somewhere. When i tried stuffing a potato down the barrel for the second time, i think there was too much air pressure building up in the chamber and it broke the fan from that square plastic thing it's in. I need to make a mental note to take the cap off the back next time i load the gun. Does a fan really make a difference?
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Unread postAuthor: DYI » Mon Oct 08, 2012 8:06 pm

But now i have a broken fan and i think i have a leak somewhere. When i tried stuffing a potato down the barrel for the second time, i think there was too much air pressure building up in the chamber and it broke the fan from that square plastic thing it's in. I need to make a mental note to take the cap off the back next time i load the gun. Does a fan really make a difference?


First, I'd love to hear about this leak you "think you have somewhere" :roll:

The fan won't break from what is essentially a hydrostatic pressure (a steep pressure gradient like a shock wave could kill it, but you don't get those from stuffing a potato down the barrel).

The cap should be off the back of the gun anyway while loading, with the fan running - why vent the chamber and load the gun as separate steps when they could be done at the same time, improving your reload rate?

HGDT does a decent job of guesstimating performance improvement from fans (note that this is based on adjusting "fudge factors" in the model to match the body of experimental data. It doesn't actually model the turbulence process - that would take weeks, at best). You'll see improvements of over 15% in many common designs using a fan. While it's difficult to talk about general cases when geometry can vary so much between builds, it should be beneficial to leave the fan running during the shot, especially if it's something fast like a Vantec Tornado. Simply having the fan in the chamber during the shot though, spinning or not, will usually improve performance. If it's going slow relative to the rate of combustion, there may not be a noticeable improvement in performance when leaving the fan running during the shot versus turning it off.

Note that all of the above is in addition to the performance improvement gained by the fan mixing the fuel mixture before the shot. My most recent 1X combustion wouldn't even fire consistently without that mixing.

Also note that, while jsefcik's "advice" should always be regarded with much skepticism, it's not physically impossible for a spinning fan to reduce performance relative to a stationary fan. It just defies what one would expect, and what is typically seen.
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Unread postAuthor: ninjamonkey127 » Mon Oct 08, 2012 9:44 pm

DYI wrote:
But now i have a broken fan and i think i have a leak somewhere. When i tried stuffing a potato down the barrel for the second time, i think there was too much air pressure building up in the chamber and it broke the fan from that square plastic thing it's in. I need to make a mental note to take the cap off the back next time i load the gun. Does a fan really make a difference?


First, I'd love to hear about this leak you "think you have somewhere" :roll:

The fan won't break from what is essentially a hydrostatic pressure (a steep pressure gradient like a shock wave could kill it, but you don't get those from stuffing a potato down the barrel).

The cap should be off the back of the gun anyway while loading, with the fan running - why vent the chamber and load the gun as separate steps when they could be done at the same time, improving your reload rate?


First off, i do have a leak. If i'm hearing air coming out the side of the barrel when i load a spud, its a leak.. I even found where the leak is coming from.

I'm pretty positive that the fan did break due to the amount of pressure building up in the chamber. I can't think of any other way it would break. Before it broke, every time i open the cap to the chamber to look inside, the fan was held in there perfectly fine, no cracks or anything in the plastic.
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Unread postAuthor: jackssmirkingrevenge » Mon Oct 08, 2012 10:31 pm

Crna Legija wrote::roll:


The device has been modified :D
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Unread postAuthor: natas » Thu Oct 11, 2012 4:40 pm

The leak u have sounds like your gas valves are not 100% tight.

second thing that hits me, it sounds like u have not ventilated the chamber with fresh air before loading in a new potato. so the gun works the first shot, but then all the air is used, and only co2 left for the next bang.

i guess thiss is a mussle loader, do you have a removable endcap so u can ventilate the chamber between shots ?

is also usefull to let the fan run between shots, to get the co2 out.

As a few have suggested here, the hose u have after the last valve is pretty long, it can also be a bit dangerous, there will be alot of pressure in that hose when u fire the gun.


hope this helps
N
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Unread postAuthor: ninjamonkey127 » Thu Oct 11, 2012 8:57 pm

natas wrote:The leak u have sounds like your gas valves are not 100% tight.

second thing that hits me, it sounds like u have not ventilated the chamber with fresh air before loading in a new potato. so the gun works the first shot, but then all the air is used, and only co2 left for the next bang.

i guess thiss is a mussle loader, do you have a removable endcap so u can ventilate the chamber between shots ?

is also usefull to let the fan run between shots, to get the co2 out.

As a few have suggested here, the hose u have after the last valve is pretty long, it can also be a bit dangerous, there will be alot of pressure in that hose when u fire the gun.


hope this helps
N

The valves are fine. The leak was coming out the side of the barrel through a small hole that was made from a screw thats holding the handles of the gun.

Yes, i do have a cap on the back.

The main problem was the spud night getting a tight enough fit when it goes down the barrel. But that problem and the leak has been fixed. I also put a new fan in the chamber today.
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