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

[oldpro]

 That is a reasonable question and a material sheet with the data needs to be in the reply or it will yield even more questions I believe. 

[Privateer]

Maybe. But your not using compressible fluids in real world application. And certainly not pressurizing that high!

[oldpro]

Maybe. But your not using compressible fluids in real world application. And certainly not pressurizing that high!

True but to inform people to the specs and material is important otherwise there are people out there whos opinion will be swayed by miss information.

[Privateer]

I'd be interested in what forum that was actually posted.
 

I'd also like to see data and comparable tests on stock tubes and see their replies.

[oldpro]

I'd be interested in what forum that was actually posted.
 

I'd also like to see data and comparable tests on stock tubes and see their replies.

I know what your saying but all I can do is provide the information and let them make up their own minds. JSAR has 3 engineers 1 Mechanical Engineer. we didnt need to do any failure tests to know it was plenty safe but we also knew it was the right thing to do. Ill have Matt post a material list and Lloyd can give his perspective on the questions.  There will all ways be questions with new products or materials.

[Privateer]

Right Travis.
Haters gonna hate and all that when they didn't have a hand in it.
(Not to mention what forum that all may have been in)

[oldpro]

Right Travis.
Haters gonna hate and all that when they didn't have a hand in it.
(Not to mention what forum that all may have been in)

I know Jeff but what can I do? Ill just give the facts thats all I can do. The material used is 2024 T3 alloy .095 wall and specs are all the same as OEM.

[Privateer]

Yep. You all are doing good!
If I had any doubt? I'd have never pre-ordered the Gen 1 tube nor sent the Hatsan tube for your look see.
 

[lloyd-ss]

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!

Sure, I will be happy to address that comment, and it is a good comment. A couple of hours of video was edited to produce the two videos of a few minutes each. Numerous measurements were taken throughout the testing that are not shown on the videos.
The yield calculation for the tube predict material yield to start at approximately 8500psi.  Yield is normally taken as a 0.2 percent permanent deformation of the tube. After the 9,000 psi o-ring failure, the deformation was measured as being 0.002" on the diameter, or about 0.16 percent, so still barely below the yield definition. Based on that measurement, one could say that yield had started and that failure had occurred. However, as the pressurization continued, the growth remained rather insignificant, as determined by measurements, and also by observation of the minimal amount of oil that was pumped into the tube.  The increase in oil volume did not really occur until about 10,000 psi, when yield and resulting elongation were fully underway. Full failure occurred at 10,000 psi.

You could say that yield had started at 9,000 psi, which would be a 3 to one safety factor for yield. Final failure was at 10,000psi, or a 3.3 to one safety factor.
Those two numbers represent good, solid safety factors for a small pressure vessel.

Required safety factors vary by certifying organization with the yield safety factor always being lower than the ultimate failure safety factor. Bob Sterne has researched the various trends in safety factors, and I hope he will chime in. As I said, suggested/required safety factors vary by organization, and even year to year within some organizations.

Again, a 3 to 1 safety factor for yield is, I believe, satisfactory and safe.

 

[mobilemail]

And I suppose for anyone who is still nervous but still, inexplicably, finds one of these tubes overwhelmingly compelling....

A Marauder can be pretty easily tuned to a performance curve only requiring a 2600-2800psi fill, increasing the safety margin by a small factor.

Now...let the smart guys carry on..

[Hajimoto]

LLoyd,


 I was asked to post the following from the gentleman that asked the question relative to the tube failure. Because he is new to GTA he was not able to respond directly.


"I just read the latest post by lloyd-ss on GTA and I appreciate his response. In addition, in no way was I trying to create trouble or ”hate” as another poster noted. My concern was only that of safety. Being a Mechanical Engineer and having spent a good part of my life working with the design of high pressure piping and support equipment, I only offered the post quoted for the concern of others. If it caused any problems or concerns, I sincerely apologize."


Thanks for everything Lloyd!

[oldpro]

 It was a legitimate and good question from someone with knowledge of the standards used I hope it answers his questions. The material if he wants to know is 2024 T3. No such thing as a stupid question.

[lloyd-ss]

Certainly no offense taken by me. Sharing of good technical information is always appreciated.
Lloyd

[Vee3]

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

Good to know. Thank you.

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.

True but generally speaking, one specifies the coating thickness required. This is standard practice (per MIL-A-8625) for all types of anodic aluminum coatings.

Side note - Sulfuric (Type II & III) anodize penetrates the material and builds up equally. If .001" thickness is specified, .0005 will be below the surface, .0005 will be on top of it. Important to know when designing anodized parts.

Type 3 would make a nice wear surface for the hammer area inside the tube...

Yes it would. Type III with a teflon seal (common practice for high wear parts) would be ideal for this application. Steel hammer (subject to side-loading during cocking) under a spring in an aluminum tube needs a little something to help prevent undue wear.

...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.

PITA indeed. You never want to mask anything you don't have to. One plating house I dealt with for many years charged 50 cents each to mask blind holes, a buck for through holes. Slots? forget it. Often charged us $10 each. We specified the coating thickness on the print and dimensioned parts to allow for it.

I've never seen anything that required both II and III on the same part. If a part required Type III in even one small area, the entire part got it. Type II & III cost us the same (but we did a lot of business with plating houses).

[KnifeMaker]

It was a legitimate and good question from someone with knowledge of the standards used I hope it answers his questions. The material if he wants to know is 2024 T3. No such thing as a stupid question.

I beg to differ Travis. I saw a stupid question on Youtube just today. LOL! 

Knife

[oldpro]

It was a legitimate and good question from someone with knowledge of the standards used I hope it answers his questions. The material if he wants to know is 2024 T3. No such thing as a stupid question.

I beg to differ Travis. I saw a stupid question on Youtube just today. LOL! 

Knife

Youtube doesnt count.....haha

[Gertrude]

I just stumbled onto this thread. I have not read through the whole thing yet, but just wanted to say it is good to see you back Lloyd.

[oldpro]

I found him hiding in his doomsday cave trying to figure out if the stalagmites could be used as transistors. I talked him back to reality now we have him among us . Glad he’s here also

[lloyd-ss]

A lotta good folks here.   This is a great place to be, especially after having met many of you at the Funshoots over the years.
Lloyd

[triggertreat]

It was a pleasure meeting you too Lloyd.  I never did catch the name of that canon you brought with you though.