Advanced combustion cannon w/ break action breach load

[jook13]

Its been a long time since I have posted on this forum. I recently got my tax return and decided it was time to start building again .
I made this advanced compustion with all the bells and whistles I could manage. It has:
-2 spark gaps (powered by bbq ignitor)
-on-board metered propane
-fan with switch and wires nestled neatly in a project box and ball valve for venting.
-break barrel with cam lock quick connect/disconnect
-56" golf ball barrel. I know it should be longer. I had it at 8 foot, but it was too bulky and cumbersome to reload.

Everything is built out of pressure rated PVC. I dont want to hear any lectures about CB ratios, I know all about it. I planned for a much longer barrel but cut it shorter for convenience. I have more powerfull launchers, but as compact as this one.

I have not shot it yet. I plan to take it out this weekened. I promise damage shots and videos.

[mark.f]

Nice to see you're still alive. Very nice cannon, too.

The break barrel action needs a little explanation, I think. I looks as if you cut some material out of that tee so that it will bend downward?

Again, nice job!

EDIT: Ah, I see a bolt from that elmo enhanced top view. Nifty.

[jook13]

Right, I'll get some close up pictures of that area.

When I make my videos this weekened, I'll be sure to show off how it works too.

[jackssmirkingrevenge]

Still at it, good to hear looks good, looking forward to the damage media

[jook13]

So I went to shoot it today. Ran into problems...

It fires maybe 1 out of 100 times. I know it cant be a metering problem. I have done the math over and over and am sure I am putting the right about of fuel in. When it does fire it packs a really big punch.

When I look in the chamber I can see the sparks, they show up everytime. My question to you guys is this: Is it possible the spark gaps are too small? They are maybe 1/16 inch gaps, I didn't think it would be a problem. Maybe it is...

This is embarrasing because my other Advanced combustion works fine

[JDP12]

hmm... thats odd. I dont think a spark gap can be too small really. If you see it sparking, that'll be enough. I don't doubt you that you know how to do the math, but honestly thats probably what it is... I would go back and double check that first. just run the calculations quick again.

[mark.f]

Are you using propane or MAP/Pro? MAPP is no longer widely available and MAP/Pro is basically propylene.

[jook13]

Propane. According to my calculations I should be using my meter at 40.6 PSI. When it does fire (like 1 out of 100 clicks) it packs a punch, it doesn't sound like a shot with too much or too little fuel. I have also tried experimenting as low as 20 PSI and as much as 70 PSI and every where in between with no success.

It seems to me like it is not sparking when it is closed, but when I open it up and look at the sparks, I see them every time. My cannon is mocking me!

edit: forgot to mention, thanks for the FAST replies!

[jackssmirkingrevenge]

hmm... thats odd. I dont think a spark gap can be too small really.

For piezos they can, something about the spark arcing across enough of the fuel/air mixture. I would suggest at least 1/4" for a normal combustion.

[jook13]

Yeah, I'll rip out and redo the spark strip... I am dissapointed.

i'll let ya all know if it works... and if it does I will still keep my promise with the videos and damage pictures and whatknot...

[jackssmirkingrevenge]

I am dissapointed.

Sorry, couldn't resist

[Combustionjunction]

Looks good try using a difrent fuel propane might be to hard to ignite with a small spark try body spray see if that works if it does try propane again or perhaps the potato is getting caught on the creas in the break barle.Really cool concept and if it works it will be amazing nice gun sorry for spelling.