broke a powertube

CJOttawa · 08-21-2010, 10:14 PM

There's another thread in the Redux section for all sorts of power tube discussions:
http://www.mcarterbrown.com/forums/r...wer-tubes.html

Well, that was a first: I snapped a #6 powertube today.

The symptom: I couldn't cock the gun, exactly the same as when the gun isn't gassed up.
After trying a few different tacks - different hammer, different bolt, adjusted TPC - nada.

On disassembling the marker, I pushed on the powertube to discover it was loose.
VERY loose.
And PULLED RIGHT OUT.
With the gun gassed up.
!!!

Degass, remove the valve nut: the tube had sheared right where the inlet vents are, ahead of the cup seal. The seal was still in place keep air from escaping the valve.

I have NO IDEA how this happened. Repeated stress? Odd. Clean break too. Oddly symmetrical.

PB Weasel has had this happen too:

Quote:

Originally Posted by PB Weasel

Well, I had my first PT partially break at the gas inlet ports, on the original mOngo PT. I knew something was wrong because the gun would partially vent the twelvie down the barrel every 15 or so shots. One of the sidewalls between the gas inlets cracked, just as yours did CJ, only I caught it before it fully snapped. Luckily I had a brand new Lapco #6 PT kicking around and cut her down with a cut-off wheel. The new one works fine, just had to screw in the TPC just under two turns to get R018 shooting at 270FPS again. Figured I would throw this out here.

ironchef97 · 08-21-2010, 10:51 PM

You pump too hard. Kidding! Was this the powertube which had the drilled out ports you were thinking of trying? Or did you never do that mod? Also was this the custom redux one or a standard #6?

jhyan · 08-21-2010, 10:52 PM

Pretty standard place to snap a nelson powertube... not a lot of meat there.

I know if the powertube unscrews from the cup seal a little it seems to break more often... so make sure it is snugged up all the time... autotriggering also can put too much stress on the part.

ironchef97 · 08-21-2010, 11:02 PM

Quote:

Originally Posted by jhyan

Pretty standard place to snap a nelson powertube... not a lot of meat there.

I know if the powertube unscrews from the cup seal a little it seems to break more often... so make sure it is snugged up all the time... autotriggering also can put too much stress on the part.

Lol...autotriggering on a redux...only possible shooting downhill.

tymcneer · 08-21-2010, 11:16 PM

Hmmmm... S7 shock steel powertubes....

Ty

jhyan · 08-22-2010, 01:58 AM

Quote:

Originally Posted by ironchef97

Lol...autotriggering on a redux...only possible shooting downhill.

Sorry... I didn't see him mention it was on a redux. I just recall this happening a lot on bushies, ghosts and carters back in the day... nelsons you could actually autotrigger to some degree of effectiveness.

PB Weasel · 08-22-2010, 03:39 AM

Quote:

Originally Posted by tymcneer

Hmmmm... S7 shock steel powertubes....

Ty

Now I know that you said that you were done making people things, but what is that^?

DSA · 08-22-2010, 10:37 AM

Your cup seal became loose which caused the weakest point of the cup seal to snap. This is very common with Nelson based markers. Solution: Loc-Tite.

Canuck · 08-22-2010, 10:40 AM

I can verify that the cup seal was NOT loose. I have the broken parts and have been unable to remove the broken "stub".

GanonsGrin · 08-22-2010, 10:43 AM

I have a Kingman New Hammer that did the exact same thing. Where do you suggest getting replacement parts for these? I called Kingman and they just said "good luck". I searched the web to find only disappointment. Any thoughts?

08-21-2010, 10:51 PM	#2 (permalink)
ironchef97 . Join Date: Sep 2008 Location: SD	You pump too hard. Kidding! Was this the powertube which had the drilled out ports you were thinking of trying? Or did you never do that mod? Also was this the custom redux one or a standard #6? __________________ Avratech R7 review \| DSP frame review Member's only deals:Duckslide, Carter buzzards and comps, Phantom, Karnivor pump

08-21-2010, 11:16 PM	#5 (permalink)
tymcneer Brass Monkey Customs Join Date: Oct 2006 Location: Baltimore MD	Hmmmm... S7 shock steel powertubes.... Ty __________________ Brass Freak compatible and Equation inserts in .670, .675, .680 and .685 Still selling brass tubing, with .678 barrel stock now available! My feedback: MCB - eBay - AO

08-22-2010, 10:43 AM	#10 (permalink)
GanonsGrin Skeet Surfer! Join Date: Aug 2007 Location: Kingsport, TN	I have a Kingman New Hammer that did the exact same thing. Where do you suggest getting replacement parts for these? I called Kingman and they just said "good luck". I searched the web to find only disappointment. Any thoughts? __________________ And my feedback http://www.mcarterbrown.com/forums/f...-feedback.html

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08-21-2010, 10:52 PM	#3 (permalink)
jhyan Cheffer Join Date: Apr 2006	Pretty standard place to snap a nelson powertube... not a lot of meat there. I know if the powertube unscrews from the cup seal a little it seems to break more often... so make sure it is snugged up all the time... autotriggering also can put too much stress on the part.