Sealed tube on 22xx?..

floydlong · April 07, 2014, 03:56:05 PM

Seems to me that if one would machine an o-ring grove in a 22xx valve and use a no-ring on it it would be a sealed tube like a QB 78/79 system. It sure would be nice to bulk it like the QBs. Has anyone attempted this? Comments?

ped · April 07, 2014, 04:39:17 PM

just use the front part of a disco valve which gets round sealing the front trigger frame hole and a disco filler cap
ped

Gippeto · April 07, 2014, 07:40:01 PM

Also need to improve valve securement.

Al

floydlong · April 07, 2014, 10:29:16 PM

Gippto,
Would I need to further secure the valve if I'm only using CO2?

And PED, do you know the Crosman part # for a Disco valve?

floydlong · April 07, 2014, 10:30:20 PM

And the part # for a Disco filler cap?

breakfastchef · April 07, 2014, 10:40:45 PM

Parts diagram for the Benjamin Discovery

http://www.crosman.com/pdf/manuals/BP1K77xx%20&%20BP9M22xx%20EVP.pdf

Regarding additional screws to secure the valve...since you would no longer be pressurizing just the interior of the valve (as in 22xx normal configuration), you would be pressurizing the entire tube in front of the valve. The extra screws provide a safety margin.

Quote from: floydlong on April 07, 2014, 10:29:16 PM
Gippto,
Would I need to further secure the valve if I'm only using CO2?

And PED, do you know the Crosman part # for a Disco valve?

ped · April 08, 2014, 01:53:10 AM

My bad for not mentioning pinning the valve also the roll stamp on 2240's and 2260's extends past the valve so would recommend you only use a 2250 tube with the discovery valve
hpa sport sell an extended valve front suitable for 2260 tubes
ped

Gippeto · April 08, 2014, 06:26:41 AM

Most definitely need to "pin the valve".

Force on the valve face with a bulk conversion on co2, could reasonably reach 440 lbs force on a warmish day. The unknown quality #6 screw is simply not up to handling this force. For what it's worth, I know a fellow who (a long time ago now) had the stock screw fail on a bulk co2 conversion...beefing up this area is really cheap insurance.

Will suggest drilling and tapping the stock screw location for 8-32 and using a QUALITY low head socket head cap screw as a good start.

This mod alone gives ~2.5x safety factor (shear value on the 8-32 screw is roughly 1100 lbs force)...not quite enough in my book, and would add an additional screw on either side of the valve. 3x (at yield) is my absolute MINIMUM for anything that contains pressure...and even quality screws are cheap...REAL cheap compared to a hospital visit.

If you need/want more information, don't hesitate to ask.

Al