New member... my baby, Big Red

Boom! The classic potato gun harnesses the combustion of flammable vapor. Show us your combustion spud gun and discuss fuels, ratios, safety, ignition systems, tools, and more.
KannonKing
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Fri Apr 24, 2020 10:26 am



"Bolt-action" sniper with metered injection, mixing/exhaust fan, "12 round" mag. Thoughts?

The barrel is what slides rather than a bolt, and when the breach is open, the checkvalve opens at the butt to allow 5 second exhausting of the chamber before reloading.

In the video, I did not switch on the fan before injection, so that would have been a misfire! :D
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mark.f
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Sat Apr 25, 2020 6:14 am

What's the construction? Using pure oxygen + fuel in plastic piping isn't a great idea. Maybe that's why you didn't actually fire the thing in the video.
KannonKing
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Sat Apr 25, 2020 10:46 am

"pure oxygen" and fuel? Maybe you noticed the vacuum pump hidden in the battery box that evacuates the chamber before filling it with "pure oxygen and fuel".
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Moonbogg
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Sat Apr 25, 2020 12:58 pm

It looks great. I was also wondering about the oxygen use regarding its safety in a PVC cannon.
KannonKing
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Sat Apr 25, 2020 2:58 pm

I have not had any problems shooting with additional oxygen. I have completed calibration using propane and mapp, but have not had enough shooting time to test with oxygen.

With plain fuel air mix I have achieved about 700 joules muzzle energy (only a 5' bsrrel, so chamber/barrel ratio is high), but some testing with an 8-foot barrel extension showed promising results).

I've cooked rounds with added oxygen (about 1/20th pressure relative to fuel) which I calculated would increase O2 content in chamber to about 22%. I fired about 20 rounds using remote trigger (2 boards and a string, pull string, board drops on igniter). I did not have the Chrony that day, but I noted a sharper rapport and a significant increase in muzzle flash.

Due to my current residence, I have nowhere to safely fire this unit (at least with this barrel and golf balls) so any further testing is off. 😒 Sadly golf balls are the least safe ammo due to the infinitely variable angles of return. And with over 800 yards range, I ain't taking that chance here.
Last edited by jrrdw on Mon Apr 27, 2020 11:13 am, edited 1 time in total.
Reason: Double post.
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mark.f
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Mon Apr 27, 2020 11:35 am

KannonKing wrote:
Sat Apr 25, 2020 10:46 am
"pure oxygen" and fuel? Maybe you noticed the vacuum pump hidden in the battery box that evacuates the chamber before filling it with "pure oxygen and fuel".
I didn't notice much of anything since you just posted a video. ;)

You sound pretty smart, we just tend to get nervous when people post pictures of plastic guns with oxygen tanks attached. I'm sure you're limiting it to a relatively tame amount of "enrichment" but there are tons of people on the internet who don't.

Overall good execution, and shame you can't get out to test it some more.
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D_Hall
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Mon Apr 27, 2020 12:48 pm

KannonKing wrote:
Sat Apr 25, 2020 10:46 am
"pure oxygen" and fuel? Maybe you noticed the vacuum pump hidden in the battery box that evacuates the chamber before filling it with "pure oxygen and fuel".
If you're pulling a vacuum before injection, what *else* would you be using?
Simulation geek (GGDT / HGDT) and designer of Vera.
KannonKing
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Mon Apr 27, 2020 1:14 pm

My apologies, I was being a little facetious, I would never consider detonating such a fuel/oxidizer mix. I thought the "miniature vacuum pump" was my obvious tell... I'll be sticking to a high nitrogen content with this device thank you very much. ;) And I'll cancel the snark until you get to know me.

I'm a graduate of the University of Burnt Latke, and Imperial College, so my credentials are pretty good.

This is pretty much exactly what I am seeing with the above described fueling. 588 fps was my fastest clock round

Image

It's like to think that with the barrel extension, I could get up here...

Image

To be clear, this is not a hybrid cannon, just using HGDT with it's most appropriate settings.
Last edited by jrrdw on Mon Apr 27, 2020 3:05 pm, edited 3 times in total.
Reason: Double post.
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Moonbogg
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Mon Apr 27, 2020 4:11 pm

Welcome to the forum! I saw Burnt Latke and knew you were a true spudman. We are united by the potato starch in our blood and propane in our lungs. Together we shall breathe fire and cough out tater tots.
KannonKing
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Wed May 27, 2020 2:27 am

Doc j
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Wed May 27, 2020 4:48 am

Pickle me grand mother.
"big belly laugh".
Dunno about ya tech thing variables golf balls.
Yeah 750 mtr range...
I av golfer, smak em 240 mtrs.
When I get onto em , Its "Anzac" on the tee.
One minute of silence, that is.... Gahahaha.
I'd Rekon I give big red, prob 5 mins of silence after seeing it in action.
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jackssmirkingrevenge
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Sat May 30, 2020 5:36 am

KannonKing wrote:
Fri Apr 24, 2020 10:26 am
"bang"
haha!

It looks promising, not many combustion repeaters out there.
hectmarr wrote:You have to make many weapons, because this field is long and short life
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