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PostPosted: Fri Aug 02, 2013 4:26 pm 
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Joined: Mon Jun 24, 2013 6:54 pm
Posts: 361
Location: Earth
If one's goal would be to have a hipac setup that they could still use carts in, would there be any benefit to using the poppet end of a disco valve over stock (or ported, gutted) 2240 valve? Fit? Pointless?

The disco valve looks longer then the 2240, but I don't have one and scale can confuse.
Disco is ready for the side screws to pin it, and is built for 2k versus 1600psi, but beyond that is there much point?
Would one be better off spending time on the stock 2240 valve and pinning it instead?

I welcome links, I couldn't find them, I looked.


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PostPosted: Fri Aug 02, 2013 4:54 pm 
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Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8978
Location: Coalmont BC
The rear half (poppet end) of the Disco valve is the same distance from the mounting holes and port to the joint with the front half as a 22XX valve.... It is a bit longer at the back end, only because the original versions had an O-ring to seal the stem, which Crosman has since eliminated (presumably to save money).... This extended portion at the rear causes two problems if you install it in a 22XX tube....

1. If the breech you are using uses the front hole for the 4-48 screw that mounts it under the bolt, that screw will hit the valve, so you need to grind a slot in the back of the valve at the top to miss it....

2. If the valve stem leaks (and they can), the puff of air that comes out can pressurize the area between the hammer and the valve, increasing the chance of hammer bounce which wastes air.... You can solve that problem by grinding a notch in the back of the valve at the bottom to uncover the vent hole which is behind the lower valve mounting hole....

In other words, you can replace the rear half of a 22XX valve with a Disco valve, but be aware of those two potential problems.... The other advantage is that the Disco valve uses a Delrin poppet instead of the brass one with a soft insert in the 22XX valve.... The Delrin is better for higher pressures (ie HPA use)....

When you drill the 22XX tube for the side screws, I would recommend using 8-32 low profile SHCSs in a high tensile material, and drilling the holes to 0.270" to fit the heads of the screws.... The lower valve mounting hole in a 22XX tube is already that size.... Drill the hole locations accurately so that all three screws are taking equal load.... This only applies if you are going to pressurize the tube using the front half of the Disco valve and O-rings, if you are just using a HiPac, simply upgrading the lower screw to an 8-32 as per the HiPac website should be good enough....

In terms of performance, the ports in a stock Disco valve are the same size as a 22XX valve.... but both can be enlarged for HPA use in .22 cal (don't change them for .177)....

Bob

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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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PostPosted: Fri Aug 02, 2013 6:57 pm 
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Joined: Mon Jun 24, 2013 6:54 pm
Posts: 361
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Many thanks for answering the questions I did not yet know to ask.
I extend gratitude for your previous posts as well Rsterne, you have enlightened many which include me.
There's something about a graphed string that makes it real, then add all these other shot strings and, well, let's just say the effort required to do that has not gone unseen. I applaud your efforts - including this one.
cheers,
Blarg


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