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Power of X to Psi Conversion

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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Power of X to Psi Conversion

Unread postAuthor: Isomer » Tue Jan 08, 2008 11:35 pm

Just wondering what certain X's are equivalent to in psi
1x:
2x:
3x:
4x:
5x:
6x:
7x:
8x:
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Unread postAuthor: LikimysCrotchus5 » Tue Jan 08, 2008 11:40 pm

What do u mean? As in atmospheric mixes for hybrids? Like a 2x mix would be 15 psi added to the chamber and 2 injections of propane.

a 4x mix would be 45 psi added and 4 injections of propane.

I think i am right, i just know that there is already 15 psi in the chamber due to its atmospheric pressure inside the chamber. To make it combustible, you add a 1 injection of propane. This is how a normal combustion works.

As for hybrids, you just keep adding air to make the mixture combustible.

8x mix would be 8 injections of propane from your meter and 105 psi added to the chamber
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Last edited by LikimysCrotchus5 on Tue Jan 08, 2008 11:42 pm, edited 1 time in total.
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Unread postAuthor: bluerussetboy » Tue Jan 08, 2008 11:42 pm

or are you asking what pressure is created after ignition?
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Unread postAuthor: MrCrowley » Tue Jan 08, 2008 11:44 pm

1x mix is already in the chamber.(atmospheric pressure, 14.7PSIA)
2x mix is 14.7PSI, 1 x 14.7PSI = 14.7PSI
3x mix is another 14.7psi, 2 x 14.7PSI = 29.4PSI
4x another 14.7, so that's 3 x 14.7PSI = 44.1PSI
etc
I think that's how it goes anyway.

edit: damn.
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Last edited by MrCrowley on Tue Jan 08, 2008 11:52 pm, edited 3 times in total.
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Unread postAuthor: Isomer » Tue Jan 08, 2008 11:45 pm

nonono, im very sorry i was unclear
i meant the pressure in psi created when differrent mixes are ignited
sorry again

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Unread postAuthor: bigbob12345 » Tue Jan 08, 2008 11:49 pm

1x:50-60psi
2x:110-120psi
3x:190-200psi
4x:270-290psi
That is all of them that I know
if they are wrong then they are wrong
but Im pretty sure its something like that
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Unread postAuthor: LikimysCrotchus5 » Tue Jan 08, 2008 11:55 pm

Haha i beat u :) @ MrCrowley
But next time be more specific
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Unread postAuthor: Killjoy » Wed Jan 09, 2008 12:20 am

Ah, I ran that stuff through gaseq a while back all the way up to 20x mix pressures, I gotta dig it up on my computer give me a few.
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Unread postAuthor: Novacastrian » Wed Jan 09, 2008 1:17 am

bigbob12345 wrote:1x:50-60psi
2x:110-120psi
3x:190-200psi
4x:270-290psi
That is all of them that I know
if they are wrong then they are wrong
but Im pretty sure its something like that


You were right when you said "it's something like that". From my experience i can achieve 65 psi at a 1x mix, although i think the correct number IS 81 psi (under optimal conditions?)
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Unread postAuthor: Killjoy » Wed Jan 09, 2008 2:12 am

Found it, but now that I look at it some of the numbers are kind of wrong (it was 2 am when I did it so thats probably why), ok I think most of the entire things is kind of off (by like 100 psi in some cases), anyways I guess it'll give you a general (really general) idea pressure wise.

20x=2315psi
19x=2200spi
18x=2080psi
17x=1970psi
16x=1850psi
15x=1735psi
14x=1620psi
13x=1505psi
12x=1390psi
11x=1270psi
10x=1160psi
9x=1030psi
8x=930psi
7x=810psi
6x=690psi
5x=570psi
4x=455psi
3x=340psi
2x=230psi
1.5x=175psi
1x=115psi
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Unread postAuthor: benstern » Wed Jan 09, 2008 2:36 am

Actually it depends on local air pressure (which in turn depends on elevation and temperature) which can vary around a half a pound or more between most shooting locations. So all those figures are complete estimates at best.

My local air pressure is around 14.12 psia
http://www.turblex.com/altitude/index.cfm
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Unread postAuthor: jimmy101 » Thu Jan 10, 2008 12:39 pm

Killjoy's numbers look pretty close. They are off a bit but more than accurate enough for spuding.

The numbers are the GasEq calculated peak pressures for propane+air in a closed chamber. The actual peak pressure in a spudgun will be a lot less, perhpas half the closed chamber values, since the projectile starts to move well before the peak pressure is reached.

Here are the first few numbers I get from GasEq (intial temp 80F, P=1 ATM)

Code: Select all
          Peak Pressure     Peak Pressure
 X             (ATMa)               (PSIG)
---------------------------------------------
1X              9.3                    122
1.5X         14.0                    191
2X            18.7                    260
3X            28.3                    401
4X            37.8                    541

For every integer increase in "X" the closed chamber peak pressure goes up by 140 PSIG.
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