GTA
All Springer/NP/PCP Air Gun Discussion General => Machine Shop Talk & AG Parts Machining => Engineering- Research & Development => Topic started by: Altinator44 on August 26, 2020, 08:05:49 PM
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Has anyone developed or working on a larger plenum for the Umarex Gauntlet?
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Check with Hajimoto. He does a lot of mods for the Gauntlet. https://hajimotoproductions.com/
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I looked into this almost a year ago, so bear with me, the exact details are a bit blurry and I don't have my notes anymore.
The plenum is a very simple steel tube. There are...again fuzzy, 3 holes to mount the bottle elbow, 4 holes to mount the hammer stop(on the .25), and 3 holes I think to mount the valve. If a jig were made to properly index the holes, it's as simple as drilling holes in a piece of seamless tubing. There was 1 threaded...add on I believe. I think it mounted to the upper receiver(?). It was not through drilled, as that would mean the threads would have to be pressurized(every other screw hole was protected from the pressurized air via an o ring on the component installed). A tab of metal was bent to the curve of the pipe, tapped, and welded to the surface of the pipe. That's the biggest challenge.
This is where it got woolly mammoth fuzzy. I THINK(measure yourself) I was looking at 7/8 O.D., 3/4 I.D tubing. I came to the decision of 3" longer than the stock plenum. Doing the math after the fact, using my fuzzy 3/4" ID, that would add 21.79cc to the plenum. It also moves the bottle forward 3 inches.
I was looking at stainless steel seamless tubing. According to a chart I found, stainless 7/8 O.D with .065 walls has a working pressure of 2800 psi. Gun ships 1900 psi, and common mod is 2100 psi, so this seemed a safe buffer. YOUR RESULTS WILL VARY!
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Well this seems to be a good start I am just surprised that no one has made screw on mod yet but it would seem this would be a labor sum task. Thanks for the reply.