Burst Test of the new Light Weight M-Rod air tube from JSA

[Hajimoto]

Aaaaaaaaand ordered! My MROD has gained a few pounds over her life. She is my primary Night Snipe rifle currently and to take 1.5 pounds off, no brainer.



Here she is with all her night ops gear on.


I will be producing an installation video of the process for sure.

[lloyd-ss]

Getting that 1-1/2 pounds off your gun will make it so it doesn't need wheels, LOL.
I hadn't seen your youtube channel before; you've got some great stuff. And it really shows me how much I need to upgrade my video capabilities. I am so far behind in that technology.

[triggertreat]

I noticed you were using SS screws or at least that's what it looks like.  Do you think there would have been a difference in the results with using OEM screws if so?

[lloyd-ss]

I noticed you were using SS screws or at least that's what it looks like.  Do you think there would have been a difference in the results with using OEM screws if so?

I don't think there would have been any difference.  SS socket heads are usually softer than standard steel socket heads, but often more ductile, unless you specifically get expensive high strength stainless fasteners. The screws bent a little bit, but the holes in the valve distorted and the tube wall sheared.  When things start twisting and bending, the failure can either be accelerated or delayed, and that is very hard to predict. 

[triggertreat]

I noticed you were using SS screws or at least that's what it looks like.  Do you think there would have been a difference in the results with using OEM screws if so?

I don't think there would have been any difference.  SS socket heads are usually softer than standard steel socket heads, but often more ductile, unless you specifically get expensive high strength stainless fasteners. The screws bent a little bit, but the holes in the valve distorted and the tube wall sheared.  When things start twisting and bending, the failure can either be accelerated or delayed, and that is very hard to predict.

I do appreciate your input and your testing efforts on this tube.  Nice to see 9000lbs before trouble is noticed.


I do/may tend to bend the rules ever so slightly at times as my gauges can differ depending on the pressure when comparing them.  From your results, this looks like a very safe tube or just as safe as OEM especially if one sticks with the 3000psi limit or very close to it.

[Dairyboy]

Aaaaaaaaand ordered! My MROD has gained a few pounds over her life. She is my primary Night Snipe rifle currently and to take 1.5 pounds off, no brainer.



Here she is with all her night ops gear on.


I will be producing an installation video of the process for sure.

You'll love it hajimoto! Big difference! Mine feels so much better but I don't have all kinds of stuff like you lol mine weighs 7.4lbs scoped now!

[Vee3]

Gotta get me one of these (gen 2). Main reason my Mrod sits unused is weight. Aluminum tube should be an option at the Crosman custom shop.

Anyone know what the weight of the gauge/block assy is? Might go without it.

I'd also like to know if the anodize is Type II or Type III.

[aluminumfetish]

I'm so happy you all are enjoying that thing!
I just brought it to Kentucky to shoot it!
 

Those bells were the most fun thing to shoot at the FunShoot. A LOT of fun !

[Geronimo]

Would the transfer port and forward breech screws have made any difference? I understand an oring will fail before the tube rips but would it have taken even more pressure with the rest of the pieces in place? I know it is impossible for 99%+ of us to reach these pressures but I知 just curious. Knowledge is power they say.

[lloyd-ss]

Gotta get me one of these (gen 2). Main reason my Mrod sits unused is weight. Aluminum tube should be an option at the Crosman custom shop.

Anyone know what the weight of the gauge/block assy is? Might go without it.

I'd also like to know if the anodize is Type II or Type III.

If you add the gauge block, gauge adapter, and the gauge together, that's another 2.7 ounces.

The guys from JSA will have to chime in on the anodize, but I am 99.9% sure it is Type 2, in black. The type 2 has insignificant thickness build-up, whereas the harder type 3 (also called hard coat) can build up a couple of thou in thickness and that has to be compensated for (thread gauging for example)  when the part is initially machined. Type 3 would make a nice wear surface for the hammer area inside the tube, but honestly, I forget how you mask a part that has both type 2 and type 3, but I do remember that it is an expensive pain in the rear.

[lloyd-ss]

Would the transfer port and forward breech screws have made any difference? I understand an oring will fail before the tube rips but would it have taken even more pressure with the rest of the pieces in place? I know it is impossible for 99%+ of us to reach these pressures but I知 just curious. Knowledge is power they say.

Provocative question, Justin, keep thinking and asking. The pressure testing of finished production assemblies is a bit like a game of whack-a-mole. You keep finding the next weakest link. This valve was plugged and didn't have a poppet in it, so when do you think the poppet might have failed?  How about the fill nipple?  The pair of 4-40 breech screws might have added another 8% of shear strength, and the T-port some more % too. But when the tube did actually fail in this test, it was kind of stuck at 10k psi, and the tube was just stretching in diameter and taking on more and more hydraulic oil.  The tube might have actually burst at 10,500, or maybe not till 12,000, I really don't know.  The only way to know when the tube itself would actually burst would be to make a test fixture for it that prevented the ends from swelling at the O-rings (like a constrictor ring around the ends) so that you could actually force the aluminum tube to burst.  But that really wouldn't have given the real life safety information we needed to know. Now I am wondering what pressure the valve poppet would fail at, LOL.

[oldpro]

Hmmm what pressure would have forced the poppet to extrude into bore or throat? I知 not certain but it is and intriguing question.

[lloyd-ss]

Hmmm what pressure would have forced the poppet to extrude into bore or throat? I’m not certain but it is and intriguing question.

Darn you Travis, you knew I'd take the bait.

[oldpro]

I値l bet it痴 long before a tube failure would happen. Should be fun watching fluid spray out of the exhaust port

[lloyd-ss]

I've got a short piece of steel M-rod tube and a stock valve body. The throat is about .23 dia, so even at 9,000 psi, the punch-thru force on the poppet is only 374 pounds. I might have to test that just to know. The shear area in the poppet is about .11 sqin (circumference of .23 dia x .15 thickness), so if the plastic has a shear strength greater than 3400psi, there is a chance it might not punch thru at 9k.  Hmmmmmm...

[SilentMatt]

I'd also like to know if the anodize is Type II or Type III.

Type II

[Motorhead]

Hmmm what pressure would have forced the poppet to extrude into bore or throat? I知 not certain but it is and intriguing question.

IMO a LOT lower !! especially in gen II valves with the raised and fairly sharp sealing surface. Likely the seats edge will create shear just as we see in used guns when doing valve service.

Just a WAG tho ...

[rsterne]

Shear strength of Delrin is about 8,500 - 9,500 psi.... Doubt it would shear quickly, but could eventually extrude if left under pressure long enough at 9,000 psi ? .... MRod poppets will start to extrude into a 0.281" throat (and the sides begin to bell out) at 3000 psi, but seem fine in a 0.266" throat at 3000....

Bob

[Geronimo]

Thanks for the answer Lloyd. I知 smarter today than i was yesterday but of course now i have more questions. Staying tuned as i know they will be answered. Awesome work guys. I wouldn稚 be a hardcore air gunner without the support of pioneers like we have here. Lucky me.

[Hajimoto]

Hey LLoyd!
 I have ordered one of these and was bragging to the fact on another forum and was informed of the following.  Can you read through it and educate me accordingly?


It was just curios if you were in any way involved with the pressure test video?  [/color][/size]Early in the video when tube diameter measurements were taken after the first pressure cycle and it was noted the change in diameter, the material had already yielded.  When designing and working with high pressure materials to be used with a compressible fluid, we consider a yield of this magnitude to be a material failure.   Any time an item is stressed to the point of exceeding the specified minimum yield strength of that material, the item has officially failed.  Testing to ultimate catastrophic failure is certainly important, but it is not a point I would ever want to use in the real world safety design rating of a product.  Hopefully those doing the video performed a calculated yield point to use for predicting material failure and fatigue related cycles.[/size]


Thank you in advance!