I got some questions.

Harness the power of precision mixtures of pressurized flammable vapor. Safety first! These are advanced potato guns - not for the beginner.
PracticallySane
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Sat Dec 19, 2020 9:37 pm

I pre pressurize the hose prior to opening the valve, that way the air forces its way in before the propane can escape.

I'm thinking that as I raise the mixture that the margins become smaller. Giving a larger window of pressure for a stoichiometric mixture?
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jackssmirkingrevenge
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Sat Dec 19, 2020 9:53 pm

Once the valve is open the mixture is going to go both ways.

I think you're running lean because of this, maybe experiment with a 15% greater propane pressure to compensate and see if it makes a difference.
hectmarr wrote:You have to make many weapons, because this field is long and short life
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Sat Dec 19, 2020 10:25 pm

I found I have to purge my meter pipe with propane to get the air out before fueling, otherwise the first shot will be weak and funky because the meter has an atmosphere of air in it.
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Sun Dec 20, 2020 9:10 am

Right on guys, ill keep tweaking things. I think it would be a good bet to lock the fuel regulator in position and adjust air pressure for compensation so I am only changing one variable at a time. One thing I have noticed is that tapping the fuel gauge will cause the pressure to fluctuate by .5- .75 psi. When there is no pressure it reads about 1 psi. Im starting to think I need to replace this gauge. Maybe even the regulator.
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Sun Dec 20, 2020 1:25 pm

So you guys were on the money. I was lean for sure. I think higher mixes helps aswell. I have been successful up to 30x with roughly 20psi propane 420psi air. Now it seems to be on par with the phenumatic counterpart.

I do intend on mounting it on a stock or something of the sort. Like a bulpup configuration. So I rearranged the components so I'm not staring down the relief port any more.

Its alot more fun with success.
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Mon Dec 21, 2020 7:41 am

PracticallySane wrote:
Sun Dec 20, 2020 1:25 pm
Its alot more fun with success.
Too right, glad you got it sorted!
hectmarr wrote:You have to make many weapons, because this field is long and short life
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hectmarr
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Tue Dec 22, 2020 9:19 pm

The piston hybrid was very good. The best thing is that you built it yourself, and you made it work correctly. Total achievement! :)
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Mon Dec 28, 2020 8:14 pm

I have ran into an interesting problem... moisture from combustion is condensing in the spark gap. If I get 2 misfires in a row I pull the plug, and sure enough there is a micro droplet of water bridging the terminal. It happens quite frequently. Unfortunately if I open the gap any further the spark plug will arc from top to bottom opposed to in the chamber at 30x.

Has anyone else experienced this problem?
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hectmarr
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Wed Dec 30, 2020 5:14 am

PracticallySane wrote:
Mon Dec 28, 2020 8:14 pm
I have ran into an interesting problem... moisture from combustion is condensing in the spark gap. If I get 2 misfires in a row I pull the plug, and sure enough there is a micro droplet of water bridging the terminal. It happens quite frequently. Unfortunately if I open the gap any further the spark plug will arc from top to bottom opposed to in the chamber at 30x.

Has anyone else experienced this problem?
The same thing happens to me, sometimes. In my city, the north of Argentina, the climate is extremely humid and hot. On very high humidity days, the first shots sometimes miss. It seems that when the camera takes some temperature, the problem disappears. With my air compressor, in my workshop, it is the same. When I use it, when I finish doing it, I have to draw water through the bottom plug, and it is quite a lot. In short, shit! :( The same thing happens to me with a pneumatic airsoft gun, self-built, all rust in the air chamber ...
The solution for me is to heat the chamber, or the spark plug, a bit so that the water evaporates.
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Wed Dec 30, 2020 8:28 am

I was hoping to find a solution to avoid removing the spark plug. I am also putting some thought into a glow plug ignition instead. Trial and error...

I was even debating placing a "silicon desiccant pouch" in the chamber to absorb excess moisture.. I figured it would end up fired out the barrel so I have not messed with that yet.

I appreciate the input, there are alot of smart guys on these forums.
I’m a scientist; because I invent, transform, create, and destroy for a living, and when I don’t like something about the world, I change it. ~Rick Sanchez.
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hectmarr
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Wed Dec 30, 2020 2:05 pm

You may be able to direct the air - mixture inlet towards the spark plug contacts. A little air with some speed might do the trick. My combustion chambers are no more than 10 cm3, and I have the gas inlet stuck to the spark plug contacts. Matter of testing.
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Wed Dec 30, 2020 2:14 pm

That is an interesting problem I've not encountered. The things you learn through experience...
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hectmarr
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Wed Dec 30, 2020 4:29 pm

Moonbogg wrote:
Wed Dec 30, 2020 2:14 pm
That is an interesting problem I've not encountered. The things you learn through experience...
Maybe you are in a place with a basically dry climate? It's lucky, if that's what I say ...
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Wed Dec 30, 2020 6:22 pm

That is a very good idea! Not bad at all, I think I will give that some kind of effort. Many thanks.
I’m a scientist; because I invent, transform, create, and destroy for a living, and when I don’t like something about the world, I change it. ~Rick Sanchez.
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Thu Dec 31, 2020 11:33 am

PracticallySane wrote:
Wed Dec 30, 2020 8:28 am
I was even debating placing a "silicon desiccant pouch" in the chamber to absorb excess moisture.. I figured it would end up fired out the barrel so I have not messed with that yet.
There are commercially available solutions that you can attach to your pump: https://www.pyramydair.com/s/a/Hill_Scr ... kring/1141

Failing that it should be relatively easy to make an inline filter containing some desiccant.
hectmarr wrote:You have to make many weapons, because this field is long and short life
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