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PostPosted: Thu Sep 20, 2018 5:28 am 
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Location: Winnipeg, Canada
Has anyone done this themselves?

If you have, how workable is it? Does it compress slightly for applications such as QB-AR?

I don't have a lathe here, but could probably turn and cut it on a drill press.
I like the idea of delrin for a port sleeve. It should be easy to get varying size inside diameters through my numbered drill set...
Still looking at ways of slightly slowing air flow for my pcp'd AR.

-D.S.

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PostPosted: Thu Sep 20, 2018 5:35 am 
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Location: Bowmanville, Ontario
Delrin can be a bit hard. Maybe try abs if you want something that may "squish" a bit to self seal..? Otherwise delrin is very workable, nice to cut.

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PostPosted: Thu Sep 20, 2018 10:28 am 
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Location: Coalmont BC
Delrin works OK, but I usually use Teflon, with about 0.010" of "crush"....

Bob

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Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Thu Sep 20, 2018 11:24 am 
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Location: Rocky Mtn Hse Alberta
I use aquarium tubing
Have had good results with straws from the Mcdonald collector cups
Not sure if they still have such?
On a drill press you could make a jig to guide a razor blade to cut the tube

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PostPosted: Thu Sep 20, 2018 11:26 am 
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Location: Rocky Mtn Hse Alberta
Missed the part where you want to choke flow
Maybe go less hammer hit instead

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PostPosted: Thu Sep 20, 2018 12:19 pm 
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Location: Winnipeg, Canada
I'm in the ball park velocity wise now- after cutting back on the hammer spring.
Looking to flatten the curve a bit- and hammer spring cutting seems to make abruptly steep changes to the way the gun behaves.

Was thinking Delrin because it would be easier to do the centered hole thing.

I was very impressed with the brass t/p in the chaser pistol, and it's shouldered steps for O-rings.
My track record for working tiny bits of brass is pretty poor though.

The Teflon idea seems to be a good one.

Going to think on this a bit more yet- no big rush on this project...

Still a great place for ideas and opinions! Keep 'em coming.

-D.S.

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PostPosted: Mon Sep 24, 2018 11:04 pm 
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Location: Canada
For choking it down, you can still use the factory steel TP...fill it with solder or epoxy and drill it to size.

For "poly tubing", I like ice maker tubing or 1/4" air line as used on air brake systems. (it also comes in other convenient sizes ;) )

Al


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PostPosted: Wed Sep 26, 2018 1:43 am 
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Location: Winnipeg, Canada
Hi Al

Am currently using .25" o.d. icemaker poly tubing. It seems to stand up quite well to any pressure I throw at it, provided it's cut to the proper length.

Came very close with the brass air line 1/4 x1/4 union- just wish it had a slightly wider, shallower shoulder profile.
Still got some digging around to do yet. :mrgreen:

I is a bit of a hoarder when it comes to anything that looks like t/p material, and there is a lot to go through.

Been toying with the idea of using a 13/22-XX port in there with a port seal on both ends. Will have to look to see how far the 1/4" mill cutter will go into the valve. I think there may be enough there. Somewhere in the junk pile there's a reduced flow 13-89 t/p that should be about the right flow rate for my purposes. Just a matter of finding it...

-D.S.

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PostPosted: Wed Sep 26, 2018 1:48 pm 
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Location: Coalmont BC
In a stock QB, I use a Crosman 22XX transfer port seal ONLY.... The square section O-ring fits into the hole in the tube nicely, and the ID is larger than the port in the receiver, so you can drill that out if desired.... You want to do smaller, so something you might consider is trying an O-ring with the same OD and a larger cross section (so a smaller ID)…. just all by itself, sitting in the 0.271" diameter hole in the QB tube.... It should squash down to allow the receiver to seat against the tube, and curve to match the convex top of the valve and concave bottom of the receiver at the same time.... There are a ton of metric O-ring sizes, for example a Metric 2 x 3mm is 0.276" OD x 0.118" ID…. that might work great.... I would expect the ID to be a bit smaller when "squashed" down between the valve and receiver.... If you need a bigger hole, select one with a smaller cross section (but greater than the 1.5mm wall thickness of the tube, so that you get some compression to seal)….

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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