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Max Working Pressure for 2240 and Disco Valve Assembly.
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Author:  Td85 [ Tue Mar 07, 2017 10:57 am ]
Post subject:  Max Working Pressure for 2240 and Disco Valve Assembly.

Hello Gentlemen,

Does anyone know the MWP for the Brass 2240 or Alum Disco Valves? I am certain the MWP would be somewhat higher than the tube, due to the smaller ID and resulting thicker wall.

Across any of the forums do any of you guys know if anyone has hydrotested a valve to failure? I have a half complete DIY hydrotest unit, and I may have to use it. But I really do not want to have to ruin a valve body without reason. I have some 4130 Tube, that I am making into a direct to valve HPA reservoir.

After a hiatus, I am eager to get back working on my now many 2240 projects. I have access to a lathe again to help move things along.

Author:  rsterne [ Tue Mar 07, 2017 11:45 am ]
Post subject:  Re: Max Working Pressure for 2240 and Disco Valve Assembly.

The valves, as you know, were never designed as a pressure vessel.... as they are contained within a steel tube that should be stronger than the valve.... I have never heard of anyone testing one to failure....

Bob

Author:  Doc Sharptail [ Tue Mar 07, 2017 2:44 pm ]
Post subject:  Re: Max Working Pressure for 2240 and Disco Valve Assembly.

I have used a disco valve at 3k psi- in a tube that was designed for it without any issues. I'm not sure how much pressure a 22-40 valve would take. Fairly certain that the stem would fail first, before the valve body. I have taken the 22-XX valves to 1200 psi and no further. More experienced voices than mine are sure to follow...

-D.S.

Author:  rsterne [ Tue Mar 07, 2017 7:07 pm ]
Post subject:  Re: Max Working Pressure for 2240 and Disco Valve Assembly.

Unless I misunderstood, the OP is intending to NOT have the valve inside a tube?.... hence why he want's to know when it would fail as a pressure vessel, to work the MSWP back from there?....

Bob

Author:  Whitewolf [ Tue Mar 07, 2017 9:01 pm ]
Post subject:  Re: Max Working Pressure for 2240 and Disco Valve Assembly.

Brass and aluminum have different fail/ shear rates due to material and their grades. Susequent rates are the same in thread design, whether it be pitch or threads per inch/ mm. Machinist and Engineering handbooks carry alot of information to address this area.
As to pressurize a valve only! not exactly sure why as it requires some form of fixture to hold it within a guns build parameters. Within a pressure tube only the holding fixtures and the stem seal face contain the pressure within the tube/ cylinder. .

Author:  Doc Sharptail [ Tue Mar 07, 2017 9:03 pm ]
Post subject:  Re: Max Working Pressure for 2240 and Disco Valve Assembly.

He mentions 4140 tubing as direct to the valve Ala hi-pac as I understand it. Such a system would still require an outer tube of some sort to mount a trigger unit.

-D.S.

Author:  Whitewolf [ Tue Mar 07, 2017 9:16 pm ]
Post subject:  Re: Max Working Pressure for 2240 and Disco Valve Assembly.

Doc Sharptail wrote:
He mentions 4140 tubing as direct to the valve Ala hi-pac as I understand it. Such a system would still require an outer tube of some sort to mount a trigger unit.

-D.S.


My miss read Missed that, but that brings us back to thread shear and material of choice. Factors to consider are thread type, its pitch, thread count and the number of threads that will be used to hold a safe working pressure. That of the combination of all being factors to a safe build.
As I believe how I'm understanding the OP, he is wanting to used the valve's internal threads to hold his pressure vessel that he wants to construct. Making his build more compact of a design. And then maybe I'm wrong too.

Author:  Td85 [ Tue Mar 07, 2017 9:31 pm ]
Post subject:  Re: Max Working Pressure for 2240 and Disco Valve Assembly.

Hey guys, thanks for replys.

I plan on making something safer than hipac with considerable wall thickness. I am obsessed with the idea of having a reservoir feed the valve directly. I plan on cutting the fore end off the 2240 tube, using the rear section for trigger group and hammer. Then the reservoir will replace the forend of maintube.

I now realize I will have to use a disco valve stem, as the seal is to soft in the 2240 valve I am fairly sure. I am aiming for higher than 2k fill pressure, this is why I am not content in using a 2240/2250 tube with disco valve/ fill adapter. A hydraulic steel -6 oring boss will hold 4500-5000 psi, so I am sure of threads etc, just not sure of the valve. Aluminum disco valve with 9/16 unf i think is too fine to hold the resulting force, which is why I am going to pressure test the 2240 valve. Have a rebuilt piston pump, married to a electric motor with crown/worm reduction, gauge that goes to 12500. And need a water tank made from 3/8 lexan or plexus for when the valve goes.

As my machining skills get better I want to try to machine a 2240 valve from steel, eventually.
I have been gearing up getting tools to single point threads, o-ring groove cutter sets etc.

I wrote this on my wife's iPad, boy is it. Pain . Sorry for litter grammar.

Author:  Gippeto [ Tue Mar 07, 2017 11:41 pm ]
Post subject:  Re: Max Working Pressure for 2240 and Disco Valve Assembly.

A couple ideas....from some of the Russian forums...some very creative fellows over there. 8)

Al

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Author:  rsterne [ Wed Mar 08, 2017 12:04 am ]
Post subject:  Re: Max Working Pressure for 2240 and Disco Valve Assembly.

So the plan is to thread a reservoir onto the back end of a Disco/22X valve?.... No idea of the MSWP of the Disco valve body, but it would be relatively easy to calculate if you know the ID and material.... or just assume 6061-T6.... The 22XX body is brass, which may not be any stronger than the aluminum.... You can replace the poppet in a 22XX valve body with that from a Disco, it slides right in.... or, for more flow and a harder material, bush the hole in the valve down to 1/8" and use a Marauder poppet.... That will easily handle 3000 psi....

Why not just use a CrMoly tube of the same dimensions as the Disco / 22XX tube.... or for that matter, just a Disco tube.... The tube is strong enough for a 3000 psi MSWP as long as you anchor the valve with three 10-32 high-tensile screws.... Surely you don't need more than that?.... If you are thinking of running more than 3000 psi, you will have extreme difficulty knocking the valve open, and will likely need to make your own PEEK poppet to survive, so at that point, you will have no use for any Crosman parts, IMO.... You could use a Titanium tube of the same dimensions up to about 4500 psi.... After that, how would you fill it?....

Bob

Author:  Td85 [ Thu Mar 09, 2017 10:59 am ]
Post subject:  Re: Max Working Pressure for 2240 and Disco Valve Assembly.

Hey Guys,

It feels great to have experienced builders comment on my thread and helping me out. :) Even ideas help my brain mill :)

Gippeto wrote:
A couple ideas....from some of the Russian forums...some very creative fellows over there. 8)

Al


Great Idea! Some great workmanship there, thanks Al!

Bob,

Its become a matter of making it myself, rather than use sourced parts. I am the kind if guy that just has to do everything at least once :D. I only plan to do it safely, and I am in no real rush. Frankly, I'm enjoying the tinkering and design.

I do not necessary plan on going to super high PCP pressures, just want to see what kind of system I can accomplish. I must admit, I did not consider the M-rod valve poppet, just found a thread where you discuss PEEK :)

The reason I ruled out aluminum was a long while ago in a Machinist Book I read it recommended to avoid fine threading aluminum, and to always use the most coarse thread pitch available in the size. Thread I am sure would be a one of the weakpoints, perhaps the most obvious.

Author:  rsterne [ Thu Mar 09, 2017 12:25 pm ]
Post subject:  Re: Max Working Pressure for 2240 and Disco Valve Assembly.

Actually, properly designed threads are incredibly strong.... they are often the strongest part of PCP reservoirs.... Generally the weakest area becomes the thin wall of the tube, between the plug and the O-ring that seals the plug into the end of the reservoir, where the tube is of the same ID as the female thread peaks.... When properly designed reservoirs are tested to destruction, the most common mode of failure is for the tube to stretch between the O-ring location and the threads, thinning the wall, before ultimate failure....

The shear strength of threads must always be calculated using the strength of the weakest component, of course.... Some aluminum alloys, such as 7075-T6 approach the strength of steel, in fact they exceed mild steel.... It's all about knowing the materials used, and designing the part to have sufficient safety margins....

Bob

Author:  Td85 [ Sat Mar 11, 2017 8:37 pm ]
Post subject:  Re: Max Working Pressure for 2240 and Disco Valve Assembly.

Hey Bob,

Thanks again for your advice and experience! Bit long getting back been busy with 3 kids and my crazy job. I originally was a Civil Engineer before I switched career paths, so the math I can do as I figure out what is relevant. However I do not know anything about thread design, just using my standard machinist chart for drill/tap and fit tolerances. I realize that PCP pressures from these valves is not realistic, and have been consulting another machinist on how to make the sealing face inside the valve. I was reading a book on hydraulic design, and re-realized that carbon steel valves may not work well in cold temps, but I doubt CO2 will freeze one. This I consider because I would like to consider CO2 fuel an option as well, would probally fuel it with CO2 until I get a PCP setup. The same book advises to safety factor in a 4 to 1 safety factor, but in some less extreme environment conditions a 3 to 1 is acceptable.

I plan on welding the end of the tube right now, with a plug milled down to fit the ID, and the the OD match the tube. The other end would use a parker weld on fitting. Overtime at work is starting to slow, so I may beable to get some lathe time afterwards to start prototyping my reservoir at least. Still plan to hydro test, want to do it in a tank of water with some leak detecting dye to help find any flaws, especially welding need to figure out a tank that is safe. I won't be testing any of my welds that do not meet my weld design specs that is for sure.

I also have a HW .25 barrel I am planning to fit onto my Hatsan 135 this week as well, so that may win the attention contest.

Author:  rsterne [ Sat Mar 11, 2017 10:14 pm ]
Post subject:  Re: Max Working Pressure for 2240 and Disco Valve Assembly.

If you Hydrotest using a liquid (oil is typical) and no air in the system, the chance of explosion on catastrophic failure is minimal, because there is nothing to expand violently.... that's why they call it hydrostatic....

Bob

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