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shooter_girl · Spammer

AirGunEric said that I posted this question in the wrong place so here it is again, and hope i'm in the right place this time.

I've been looking at 2240 photos on this and others sites and noticed that a lot of the 2240's that have been rebuilt have longer tubes that look like my 2250, and most of them have screws in the sides of the tubes. Why change the tube I got a bulk-fill adaptor tube at the show and have it in one of my 2240's. It works fine but the pictures have me wondering if i'll need to bolt the valve into the tube.

Someone please explain.

rsterne · Moderator

The valve in a 2240 is not fastened in strongly enough if you bulk fill with CO2 or use HPA (high pressure air).... In the stock setup, only the valve is pressurized, not the tube, so there is little end force on the valve compared with when you bulk fill....

The extra locating screws are needed for your safety....

Bob

AirGunEric · Site Admin

If you look at that single screw that holds the typical 2240/2250/2260 valve in place- it isn't even solidly mounted- it holds the valve in place by having it's head act like a wedge in a hole that allows for a fair amount of movement. As Bob pointed out, that may be fine in a limited (into the valve only) Co2 application, but not a very solid idea in other circumstances.

packrat · Senior Member

shooter_girl---let me suggest that you read the thread I posted just below...there is a virtual wealth of information in that thread..though it is written in conjunction with a rifle build probably at least 95% will be applicable to pisto;s as well....it will answer a LOT of questions you may have...when I first got interested in HPA and PCP I knew NOTHING....just this one thread really opened my eyes...do yourself a favor and read it all!!!! GOOOOOD STUFF !!

http://www.airgunhome.com/agforum/viewtopic.php?t=3165

shooter_girl · Spammer

shooter_girl · Spammer

AirGunEric · Site Admin

You can do all sorts of things to work around the single, poorly mounted screw.

Depending on the configuration of your specific bulk adapter, perhaps nothing needs to be modified. However, not knowing that your adapter's specific configuration is/isn't- we cannot answer specific questions about it.

That being said, in a HPA or bulk-feed application where the tube itself gets pressurized, the 3 screw idea may be the best solution (especially if HPA running at 1400+ psi). As well, if the tube is pressurized, something will need to be done to seal around the valve. In order to get better efficiency, many people have used the valve from a Benjamin Discovery in these situations, which is aluminum and has 3 screw mounts in it already (and two outer o-rings to keep the pressure in the tube).

rsterne · Moderator

The seal between the stock powerlet and the valve is only about 1/4" in diameter at the sealing surface.... Even on an extremely hot day (CO2 can reach 1900 psi at 120*F) that works outs to about 93 lbs of end force on the valve....

Once you pressurize the tube, the diameter exposed to the pressure increases to 3/4".... At the same pressure, the force increases by 9 times to 839 lbs.... At 3000 psi, the end force on the valve would be 1325 lbs....

The screw that locates the valve is a 6-40.... That has a minor diameter of 0.1065".... Safe working load in shear should be calculated at 20,000 psi which gives a safe working load of 178 lbs.... It's pretty simple math from there.... The screw has a 2:1 safety margin as designed by Crosman.... but is overloaded by nearly 5:1 in a bulk fill on a hot day.... That puts it over it's likely shear point.... On HPA with a regulator failure, the load will cut that screw off like butter with a hot knife.... and yes, it has happened even with a bulk fill on CO2....

I understand that you are convinced by your experiment that what you are doing is safe.... The "Powermax" is designed to only pressurize the valve, and as such, at 2,500 psi should only put the stock screw under a load of about 122 lbs DUE TO THE PRESSURE ALONE.... this does not take into account the additional force generated by screwing it in to make it seal.... In addition, if the seal were to fail, since the valve is not sealed into the tube, the air pressure should leak out safely, although the momentary load could easily be enough to shear the screw....

The good news is that as long as the gun is assembled at the time of failure, the valve is unlikely to come flying out the back of the gun.... It would have to shear off the breech retaining screws and blow the hammer seat out the back to do that.... boy, it would sure scare the heck out of you, though.... Shocked

Many engineers have looked at the way the 22XX valve is retained and every one I know of (with any brains) says that for safety the valve needs to be retained properly if the gun is bulk-filled or used with HPA.... In the Discovery, Crosman use three 8-32 screws to locate the valve, and that gun is only designed for 2000 psi.... I think that is the bare minimum required, and I'm not alone....

There is an additional problem in pressurizing the tube on a 22XX.... In most cases there is a safety warning pressed into the tube by a method called "roll-stamping".... I have seen examples where the letters are so deep into the metal that they have distorted the inside of the tube.... This area is basically weakened much like the pineappling on a grenade.... and if subjected to sufficient pressure, will fail with similar results.... ie schrapnel.... In conjunction with yourdaddyjoe on this forum (MuzzleMack Products), I developed an extended valve front end that places the O-ring which is required for bulk-fill CO2 or HPA ahead of the roll-stamped area for safety.... If you are contemplating pressurizing the tube, PLEASE check into this to save possible wear and tear on that pretty face....

One other thing you should be aware of.... the manufacturer of the "Powermax" was thrown off this forum because he ignored safety warnings.... and continued to plug a commercial product without permission.... IMO, his product is safe provided it is not overtightened and a seal failure does not occur which suddenly pressurizes the tube.... Since properly engineered products are safe even with reasonably induced failures.... I remain unconvinced.... Rolling Eyes

Bob

shooter_girl · Spammer

All those numbers got me head aching. I still don't know what that all means. I talked to the powermax guy. He had a nice little table with some things I hadn't haden't been able to find. He didn't say anything bad but he did mention bob. Even has your name on the instruction/caution flyer that came with it so I asked who bob was. He said that they say you know everything and that it was just as safe to retap and replace the set screw with a bigger headed screw. Then he told me not to use a wrench to tighten it in, duuuh. He did show me how to do it and where to cut the frame behind the spring. I grinded the head and sides flatter (well, hubby did because I told him to) and removed a little meat from behind the spring. Haven't done it to my new 40 yet but it's still holding up. I just don't like the look of all those screws. It's really gonna ruin the paint job I have planned for my girls. Hot Pink is the color of a true huntress:oops:

Jaxom · Senior Member

Just my two cents here. If it's a matter of safety vs appearnce, I do believe most would pick safety first. Even if you were to retap the single screw so it could accept a larger one, that's still only one mount point.

Think of it like this...you've just installed brand new carpeting, then you want to put a plant on a stand, which would you choose, the single legged pedistal...or a three legged stand?

This is one of those cases where more is definetly better. Perhaps you can dress up the screw heads to cooridinate with your planned paint job? Ya know, use some other color or chrome them or something. That would stand out and say I'm good lookin' AND safe!

AirGunEric · Site Admin

AirGunEric · Site Admin

Hell- I'm not even going to hold back- Rodent/Shooter is a complete douchebag. Who has time for his stupid games- obviously he's another loser with too much free time trying to flog his dubious sh!t. I suspect the only reason we didn't catch on to him sooner is that we believed the pretext that this was just a "lady" looking for some assistance.

Mark5043 · Silver Status Member

What a LOOOOOOOOOOSER! Faq-U

I have to admit I was fooled by this lunatic f--kwad.... Rolling Eyes

rsterne · Moderator

Well, I fell for it hook, line and sinker, didn't I.... Shocked

Some people never learn.... Rolling Eyes

.... Thanks, Eric....

I normally don't wish people ill, but I hope this jerk ends up with a valve imbedded in his skull.... or happens to be holding his roll-stamped 2240 at groin height when the seal fails and it turns into a grenade.... Faq-U

Bob

kanyon · Silver Status Member