Our modified 2240 valve got some pretty impressive chrony numbers yesterday.

[Gertrude]

 Our "Quest" to find the highest FPE possible, using a (modified) Factory 2240 valve body, (and as many Factory Crosman Parts as is possible), continues....

I spent yesterday at my buddy Jeff's house, doing some more tinkering and testing our latest 2240 valve mods and then running some lead across the chrony. We are installing these heavily modified valves in our "Frakengun" builds, using 18" Crosman .22cal barrels.

 We have now bored the valve body plenum walls .030 wider than stock, opened up the "throat" section to .250", opened up the TP to .180, dremeled the angle into the bottom fwd side of the TP port. We then bored the rear of the valve, installed a .003 interference fit brass slug, and then redrilled it to .124 to fit the smaller shaft size of a factory Crosman 760 poppet, which also has a much smaller OD on the overmolded "Head"of the valve.
 We have machined a free flow front half valve body, much the same as many others before us have done, to convert this valve into a HPA application, and are using a conical type spring on the poppet.
 Mounting screws are upgraded from the 6-32 to 8-32, and extra's are being added on the sides.
 valve is being fired using P-rod trigger group, w/ JB Weld modded hammer, Disco spring w/ shim approx. .060 thick.

 Chrony testing was done tethered to a large fill bottle, and pressures were manually maintained for each shot using high end gauges that have been verified to be accurate within 25-30psi. Chrony used was a new Caldwell Ballistic Precision Premium Kit with the IR LED Light Kit, and was approx. 4' from the muzzle.
We shot "5 shot" strings with various pellets, and the FPE numbers below represent the highest FPS for each pellet tested.

Here's what we got at 1800 psi,

CPHP 14.3 gr ------------------ 1007 to 1012 FPS - 32.53 FPE
Predator Polymag 16.1 gr -------- 972 to 976 FPS - 34.06 FPE
JSB Match 18.13 gr -------------- 930 to 937 FPS - 35.35 FPE
H&N Barracuda Match 21.3 gr ---- 902 to 909 FPS - 39.09 FPE
JSB Jumbo Monster 25.39 gr -----845 to 846 FPS - 40.36 FPE
Skenko Newboy Senior 28.6 gr --- 818 to 821 FPS - 42.71 FPE


Then we ran one shot each at 1500 psi. Here's what we got,

CPHP ------------ ----956 FPS - 29.03 FPE
Polymag ------------- 933 FPS - 31.13 FPE
Barracuda Match ---- 863 FPS - 35.23 FPE
Newboy Senior ------ 779 FPS - 38.41 FPE


We are wondering how these numbers would change using a 24" Disco Barrel ?. HMmmm,...
 We will be machining the same mods into Jeff's .22 Disco valve soon to find out .

For the 18" barrel, I am also considering opening the barrel port a few more thousandths, then slotting it a few more thousandths, and machining up a custom Delrin TP seal with ID to match.
 I'm trying to get these numbers up high enough, to justify putting my B&A .25 barrel on this current Frankengun build.
 I'd really like to see that eventually happen, providing I can get a .25 JSB King 25.39 gr to run out at around 870 - 900 FPS... but I'm just not sure if that will be possible at 1800psi.
 Until, (if),... we can determine with any certainty, that the 2260 air tubes are the same material (?) as the Disco air tubes, I'd like to not go over the 1800psi mark.
 

[Onebaddj]

Thats some pretty impressive numbers. Nice work. Cant wait to see what the next round of tinkering will bring.

[rsterne]

Pretty much made a modded Disco valve out of it (since the back half is functionally identical), so the numbers are not that surprising.... but certainly fun to do, nevertheless....

Bob

[ped]

 Until, (if),... we can determine with any certainty, that the 2260 air tubes are the same material (?) as the Disco air tubes, I'd like to not go over the 1800psi mark.
 
[/quote]
I read an interesting article by mike at tko(think it was mike) about some pressure testing he did on 2260 and discovery tubes might be worth trying to find it then you can draw your own oppinions was on the crosman green forum I think

[rsterne]

I know of one 2240 tube that was tested to 10,000 psi without failure, and it even had a roll-stamp.... What I don't know is how deep the roll stamp was, and they vary a LOT.... I personally feel comfortable using 3000 psi in a 22XX tube PROVIDED the roll-stamped area is not pressurized.... but that is me, I'm not recommending it to anyone else.... 1018 DOM tubing that is 0.875" OD x 0.065" wall has a safety margin of 3.1:1 at 3000 psi, and 1026 DOM tubing is 4:1.... However, at a minimum you need to use three high-tensile 8-32 SHCSs with the head taking the load into the tube wall, just as you would with a Disco.... and 10-32 is even better.... Do NOT use the stock Disco valve screws, or unrated ones from a hardware store, at those pressures....

If you have a link to Mike's article, I would love to see it.... The test I am referring to was a Hydrotest by Walter Glover (Voltar1).... The only thing noticed was the 8-32 screw heads settling into the pockets in the tube until the load was equally shared, at about 7000 psi.... He stopped the test at 10,000 psi.... Lloyd has some excellent tests on Video right here on this Forum, in the PCP Gate....

Bob

[Gerard]

You can remove all the worry about the roll-stamped portion of the tube by adding a regulator. Robert Lane makes one specifically for the Crosman/Benjamin tube ID, his CO2/HPA conversion regulator. Comes pre-adjusted to whatever pressure you specify at time of order, or is easily adjusted. I got one to put into my HiPAC (had to turn down the OD just a hair but the Lane O-ring groove depth worked out just fine) on a 2240 and shooting at around 800psi works nicely for my setup. Cranking one up to 1,400psi or so should give you enough juice for a heavy-hitting 22xx without excessive strain on the valve retention bolts, while giving you much more consistent velocity for however many (or few) shots you're after. A regulator takes up valuable volume, but the Lane is pretty tiny. Even allowing for a significant plenum volume for higher power you might still see benefit, even if it's just for 3 shots at a 3,000psi fill, the ES dropping to almost insignificant.
http://airgunregulators.com/pcp-regulators/co2-duel-fuel/mk6-co2-duel-fuel

[rsterne]

You can remove all the worry about the roll-stamped portion of the tube by adding a regulator.

What happens if the regulator fails?.... Do you not end up with 3000 psi (or whatever your fill pressure is) in the plenum and valve?.... IMO, any regulated gun should be set up to be safe in the event of a regulator failure.... and don't say it doesn't occur, because is does.... A QB79 suffering such a failure with a nearly full HPA tank can, and likely will, fail, shearing off the tank block screws and sending the tank assembly flying.... I know of this happening at 2600 psi because the regulator in question was not fitted with a 1.8K burst disc, and allowed the gun to see the full 2600 psi.... My advise has always been that if using a 22XX (or QB7X) on HPA with a regulator, unless you build the gun for 3000 psi, and the roll-stamped area is not pressurized, to make sure the gun is protected by a 1.8K burst disc.... I don't think that is the case with any of the "in-tube" regulator, please correct me if I am wrong....

Bob

[Gerard]

Sorry Bob, I was over-stating the 'no worry' I suppose and that's never a good idea with high pressure systems. In my case I went from running the full 3,000psi in the HiPAC directly touching the valve face seal (ertalyte stepped seal I fitted to a modified seal area which allows for a press-fit of this hard plastic part) as per normal HiPAC setup (though his seals are garbage), so the inside of the valve saw 3,000psi, not the Crosman tube. I had installed 10-32 screws on both sides as well as a 10-32 into the bottom of the valve, and there was never a trace of deformation behind those in the tube wall. So I know my valve is secured against the full 3,000psi, but also that the valve is only receiving 800psi as it's now only getting regulated pressure. Should the Lane regulator 'blow out' somehow I know my valve is up to the task, though it seems likely the vent hole I drilled between O-rings in the regulator would bleed off that pressure to the outside air. Loudly, but fairly quickly removing all pressure.

So yes, of course the valve should be properly retained against full fill pressure, even if it never sees that pressure in actual use.

[ped]

I know of one 2240 tube that was tested to 10,000 psi without failure, and it even had a roll-stamp.... What I don't know is how deep the roll stamp was, and they vary a LOT.... I personally feel comfortable using 3000 psi in a 22XX tube PROVIDED the roll-stamped area is not pressurized.... but that is me, I'm not recommending it to anyone else.... 1018 DOM tubing that is 0.875" OD x 0.065" wall has a safety margin of 3.1:1 at 3000 psi, and 1026 DOM tubing is 4:1.... However, at a minimum you need to use three high-tensile 8-32 SHCSs with the head taking the load into the tube wall, just as you would with a Disco.... and 10-32 is even better.... Do NOT use the stock Disco valve screws, or unrated ones from a hardware store, at those pressures....

If you have a link to Mike's article, I would love to see it.... The test I am referring to was a Hydrotest by Walter Glover (Voltar1).... The only thing noticed was the 8-32 screw heads settling into the pockets in the tube until the load was equally shared, at about 7000 psi.... He stopped the test at 10,000 psi.... Lloyd has some excellent tests on Video right here on this Forum, in the PCP Gate....

Bob

this is it Bob

Having built over 50 PCP conversions of the 2400KT and derivatives, I have some experience with the issues of using various tubing for the pressure vessel.

 I also have access to some of the most advanced hydro equipment in the world, currently being used to test very large 4,000 to 10,000 PSI CNG tanks.(Compressed Natural Gas used for transportation: buses, cars etc.)

 I have hydro'd 4 Crosman/22xx/Discovery airgun pressure tubes to purposeful failure over the span of about 2 years.

 Each tube used the standard Discovery valve, secured with 3 screws.
 Each tube was fitted with a standard fill adapter, with the check valve removed. (Removing the check valve allows a rapid cycle testing of the vessel ... over 15 cycles per minute with the very small volumes of the tubes.

 One tube also had the fill adapter threaded on AND "pinned".

 One tube was a Discovery tube.
 One tube was a Crosman 2260 tube with a "pinned" valve using 3 screws 120 degrees apart. (Not using the 90 degree holes in the factory valve.)
 One tube was a stainless steel tube.

 IN THESE THREE CASES, THE FAILURE OCCURRED WHEN THE FILL ADAPTER WAS STRIPPED FROM THE TUBE.

 Examining the tube and fill adapters after the failure showed that the very short thread involvement of the fill adapter (less than 1/4" total length) stripped the threads of the tube and also marginally damaged the fill adapter threads. The attending engineer said he was kinda of surprised the length of the threads wasn't closer to 1/2", and he did some involved calculation of thread depth/material and surface area shear. He said it was within the PSI rating of the vessel, but considerably short of their DOT requirements for vehicle CNG fittings ... by a wide margin.

 (Photo of a fill adapter showing the fine threads and short thread length.):
[linked image]

 No other damage was found on any of those three tubes. Temp-Plate/LCC labels showed no tube deformation.

 Each adapter failed at different pressures, with a failure range of 3250 PSI (as I recall ... Low to high.)

 The fourth tube (2260 tube) also contained a pinned fill adapter. That tube split about 1/2 way between the fill adapter and the valve head, on what would be the lower "side" of the tube. The tube split at 2700 PSI higher than the highest pressure of the fill adapter failures.

 After my 2nd test, I have since started torquing the fill adapters to the airtubes in recent builds in an effort to determine thread fitment. 120 in/lbs. gives a good indication of thread involvement.

 I have photos of the tubes somewhere in my computer server, but can't seem to find them.

 Someday I'll hydro a complete gun with a tube sleeve and pinned adapter to force valve failure, just to see what it would take to get the valve to exit the rear of the gun. Might be surprising to some what kind of pressures these little screws and tubes can handle.

 Take care and be safe,

 Mike T.
 TKO - Omaha, NE USA
 402-889-9222

[rsterne]

Highly unfortunate that the pressures at which the fill adapters pulled from the tubes is not stated, only that the range (low to high) was 3250 psi.... we don't know if that occurred at 5,000 psi, 10,000 psi, or 20,000 psi.... Although Mike states that the valve was secured with three screws, we don't know if those were stock Disco valve screws or not.... Lloyd tested stock Disco screws and found that they sheared at the equivalvent of about 7000 psi, while high tensile 8-32 screws went well over 11,000 psi.... There is also this article from when the Disco first came out that tube and valve assembly was tested to 11,000 psi, and the tube itself to 15,000.... http://www.americanairgunhunter.com/benji_discovery.html

All the tests except this one that I am aware of have NOT used the Disco fill fitting.... so it would sure be nice to know if the threads in the tube stripped out at over 11,000 psi (as per the article), or less than that.... I know Mike reads this Forum on occasion, perhaps he could give us that information?....

Bob

[nervoustrigger]

I don't mean to beat a dead horse here but I think it's worth mentioning that it's not so much a matter of if a regulator fails, rather when it fails.  If you keep a regulated rig long enough, it will fail.  The seat on most if not all HPA regulators is a semi-rigid plastic that will eventually develop a leak.  If you're lucky, the output pressure will just creep up a bit before there's enough "squish" to get it to seal.  If it goes unnoticed, it will just continue to worsen until something gives.  And hopefully that something is a burst disk and not a valve or a bottle.

[vigilandy]

I don't mean to beat a dead horse here but I think it's worth mentioning that it's not so much a matter of if a regulator fails, rather when it fails.  If you keep a regulated rig long enough, it will fail.  The seat on most if not all HPA regulators is a semi-rigid plastic that will eventually develop a leak.  If you're lucky, the output pressure will just creep up a bit before there's enough "squish" to get it to seal.  If it goes unnoticed, it will just continue to worsen until something gives.  And hopefully that something is a burst disk and not a valve or a bottle.

+1 on this.  I've had two regs "fail" on my Ninja tanks.  "Fail" is in quotes because these were Ninja SHP regs shimmed to increase output to 1400.  Can't really blame Ninja.  They were in use for a 2-3 months before failing.  Fortunately they also had 1.8k burst discs!   

I think I may be doing something wrong seeing how the reg that Jason set up at 1500 psi has been working just fine for about a year now. 

[ped]

a bit more from the thread
The pressure "spread" from the lowest pressure failure to the highest was around 3250 PSI.

 The lowest fill adapter failure was 6300 PSI (Stainless tube), highest was around 9500 PSI.

 Something I should mention ... when pressure testing with equipment as big as I was using, it can pressure cycle (complete) a small vessel in about 4 seconds. Do that 10 times in a minute and seal failures become more likely. Heat builds very rapidly. Even though the tubes are suspended in a water flooded concrete flask.

 I had plans to test another tube with an extremely slow fill rate, as it was predicted by the AE that the failure pressure would be much higher. Airguns are usually filled at a very slow fill rate.

 The attending engineer mentioned factors like the type of lubricant used to lube the o-rings that may remain on the threads during assembly can skew the failure point.

 Pressure vessels have two "moving-target" safety values... Highest pressure of the entire system, and number of fill cycles. Even the fill cycle number is a variable, as seldom does a airgunner fill their gun from completely empty. Discovery users fill from about 1K to 2K.

 I should also have mentioned that the first test was designed to simulate a worst case fill scenario ... Filling a Discovery from a full 6K Nitrogen tank in 2 seconds.

 Regarding the last thread on the tube being weak... since the fill adapter is sealed forward of that in to the minor diameter of the tube, the only stress at that point is shear, not pressure.

 I have a meeting with the AE about another project and I'll see if he has some trace data from our adventures!

 Take care,

 Mike T.

[Gertrude]

I'm curious here now.
So with these numbers,  would that indicate the tubes for the 2260 and the tubes for the Disco are of the same or equal material ?

[james]

Those are some impressive numbers.I wonder what increasing the diameter of the chamber 1/2 inch on a red ryder or buck would do for its fps?To clarify I would like to have it built with a larger diameter air chamber and pistonalso a stronger spring.I am not confident a Buck or red ryder can be hot rodded.If however it was done that way from the factory I think it could work well and not be much bigger heavier than a current model maybe the model name could be the Daisy Moose .It would of course have an adult size stock.What i would not want to change is the repeater function having 400 or 650 bb's to play with is mighty nice.A cock and shoot bb gun is great for plinking a higher cocking effort within reason would not be a deterrent.

[rsterne]

It would appear that the results indicate that the steel used in the 2260 and Disco tubes has a higher shear strength than the stainless steel used, in any case.... Whichever tube (2260 or Disco) failed at 9500 psi (by having the fill fitting pull out) had a safety margin of over 3:1 at 3000 psi.... DOM 1018 Steel tubing the size of a Disco tube (0.875" OD x 0.065" wall) has a theoretical burst pressure of 9500 psi, so the tubes would appear to be better than that, as the 2260 tube tested with the pinned fill fitting let go at (9500 + 2700) = 12,200 psi.... That is right on the theoretical burst point for 1026 DOM tubing, so that could be what Crosman use.... it would be safer to assume they use the less expensive 1018 DOM tubing, and with a 9500 psi burst strength, and that being what the fill fitting stood (the best one), it would seem that with the proper valve screws a 3000 psi fill should give you about a 3:1 safety margin....

Remember, Lloyd managed to shear the stock Disco valve screws at the equivalent of about 7000 psi, however.... It took high tensile 8-32 screws to get over 10,000 psi, so that would be the minimum for a 3000 psi fill to get that same 3:1 safety margin.... Using a Disco Fill Fitting, you should never exceed that.... Thanks Mike for those results....

I wonder if the rapid cycling and heating made the tube expand, helping it to shear along the Fill Fitting threads due to the decreased overlap?.... Just a thought.... but as you said you were after an accidental, worst case, 2 sec. fill to 6000 psi....

Bob

[Gertrude]

So are we now comfortable with taking a 2260 tube to say 2200-2500 psi with a Crosman cap and 8-32 screws in a 2240 valve ?

[rsterne]

I personally prefer not to pressurize the roll-stamp area.... simply because they vary so much.... I have seen ones so faint you can hardly read it, while others are stamped so deep there are actually marks on the inside of the tube.... You can't tell me that hasn't compromised the strength.... Well, you can, but I won't believe you.... My personal comfort level is I have no problem using any 22XX tube on HPA providing the gun is protected by a 1.8K burst disc.... I have done 3000 psi 2260s, but I use an extended valve front end so that the O-rings seal ahead of the roll-stamp.... and I use three, 8-32 high tensile screws in a Disco style valve.... You could use the rear valve body from a 22XX, and drill and tap it for three such screws.... and then replace the poppet with an upgrade.... but why would anyone bother doing that when a Disco valve is exactly what you need and they are cheap, and already drilled for the screws.... Stay under about 2400 psi and you can use the stock Disco valve screws as well....

Bob

[Gertrude]

Thanks Bob,
I agree on the valve extension and oring past the roll stamp, and as far as the Disco valve vs 2240 valve, I just like the brass over the aluminium. Doubt that I'll really want to go up to 3000 psi,  but was hoping to achieve 50 fpe in .22 on the 18" barrel.
Probably won't happen, but is fun trying.

[rsterne]

Anything you can do to one, you can do to the other, brass or aluminum.... so it's really up to you.... They have exactly the same internal dimensions to start with, but the Disco poppet is more suited to HPA pressures.... If you want a cute trick, get an MRod poppet and sleeve the stem hole in the valve down to 1/8" by using a short piece of K&S brass tubing from any Hobby Shop.... You can glue or solder it into place.... OOPS!, I see you did something similar already!.... Me bad!.... *LOL*....

Bob