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Old 04-24-2014, 09:18 AM   #1781 (permalink)
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RNS, magic nipple is a device installed in the trigger frame of a Retro, in the gas transfer port which feeds the valve. Not part of the valvetrain itself.
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Old 04-24-2014, 11:30 AM   #1782 (permalink)
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another issue i would like to fully address is wasted gas. there are several places gas seems to escape in the system when firing. underboring magnifys this issue. i am adding seals wherever i can without adding cyclic friction.
Totally agree with this - the interface between the bolt tube and power tube seems the most troublesome to me. an o-ringed bolt would help too, but at some point you're giving up pump stroke feel, yea.

I finally slept reasonably last night so I can try to get you the updated drawings tonight, sorry I've been a real piece (life)
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Old 04-24-2014, 11:35 AM   #1783 (permalink)
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How much pump stroke feel would you really be giving up with a teflon or other low friction oring in the bolt on the power tube? The oring doesnt have to be crammed on the power tube to seal. Stiction doesnt seem to be a big deal with this, the bolt on my buzzard gets slightly stuck into the sleeve on the freak barrel (which is why my wonder .790 brass insert is permanently in my deadlywind barrel, its jammed). Causes a bit of a hitch, but you dont notice it when you're playing.
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Old 04-24-2014, 12:12 PM   #1784 (permalink)
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Uhh what? How are you going to put an oring on that part... The wall thickness is very thin and this is constrained by various elements (through bore of the hammer, ID of the hammer spring). I really don't think any pressure worth saving is being lost there, so close to the ball. The tiny gap between valve nut and PT is the only place to make any gain and even then... Barely. And only because it's a forward facing gap, in immediate proximity to the high pressure of the valve.

Regarding the through bore of the hammer, you can only go so big without interfering with room for the sear spring.
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Old 04-24-2014, 01:42 PM   #1785 (permalink)
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You could groove the ID of the bolt and get an o-ring or other seal in there without grooving the powertube. It would require a new bolt design without a TPC I think. Or at least just not the standard CCI TPC.
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Old 04-24-2014, 01:44 PM   #1786 (permalink)
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You could groove the ID of the bolt and get an o-ring or other seal in there without grooving the powertube. It would require a new bolt design without a TPC I think. Or at least just not the standard CCI TPC.
Thats what I was thinking.
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Old 04-24-2014, 02:32 PM   #1787 (permalink)
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The tip of the powertube doesnt sit very far into the TPC at rest, at least not in a phantom. You dont want to mess to much with the stock clearances, due to the mobile nature of the bolt and hammer they need plenty space to move without binding.

RNS: Ghost pilot suggested making a teflon ring to press into the valvenut instead of an oring, maybe thats worth considering.

Last edited by Wizbaa; 04-24-2014 at 09:40 PM. Reason: mobile phone
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Old 04-24-2014, 03:31 PM   #1788 (permalink)
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there are plenty of ways to go about doing this and i am open to all. I will be at supergame next week and will pick up a few extra sets of internals from mike.

i have had good experience with U cup piston seals. very low drag and good sealing.
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Old 04-24-2014, 08:26 PM   #1789 (permalink)
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So I guess I'll go into further detail as to why it's not actually possible to add a seal at the end of the powertube near the bolt end:

1- the maximum powertube protrusion from the face where the hammer hits it, is 2.2 inches. any longer, and the PT will stick into the breech and prevent paint from loading. furthermore, any powertube close to this length would be sitting right behind the ball, and fire a jet of pressure right into it and cause paint breakage... no room to expand (unlike in TPC and other velocity adjusters in *all* the high end nelsons)

2- the theoretical length of extended powertube required to bypass the mainspring constraints (which limit the maximum diameter of whatever rides inside the spring to .360 thou), would be 2.3 inches. as you might gather, this figure is not compatible with the aforementioned constraint of powertube length.

3- working within said mainspring constraint of .360 OD max, and assuming one of these "standard" powertube outside diameters, the following wall thicknesses of whatever rides over the PT (in this discussion, theoretical but implausible room for an oring or seal) are provided:

phantom PT, diameter .235: wall thickness to spring = .062"
nelspot or lapco PT, diameter .246: thickness to spring = .057"

even in a carter buzzard, which uses a larger diameter hammer spring (which limits options for choice of springs), the resulting calculation is .380 OD max with a PT diameter of .250 resulting in .065 thickness allowance.

none of these allowances are even close to enough to provide for both a reasonably durable seal, and a reasonably durable and mechanically viable component. and since it's not possible to bypass the diameter constraints of the mainspring by "reaching past it", there's basically no way to improve here beyond ensuring a close fit, without causing frictional issues... for example, by using a brass velocity adjuster over a stainless powertube. both the Buzzard and Retro use brass adjusters for this purpose.
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Old 04-24-2014, 08:38 PM   #1790 (permalink)
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We're not talking about changing the PT at all.

The bolt velocity adjuster itself, near the back would be changed. I, am more familiar with the classic trracer guts and the buzzard guts than standard nelsons. In both cases a larger diameter rear section of the adjuster to facilitate the oring would be required facilitate the oing but should still fit inside the hammer spring in both cases. The buzzard bolt is also really short so the velocity adjuster back side would probably have to be made longer. I have zero interest in changing the power tube.

And my buzzard has a green cocker main spring.
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