Destructive Titanium Airtube Testing.

[Ca_Varminter]

Here some info that I have been ask many times...
So I wanted to share this valuable information!

The Titanium tubes samples were made by Chip Smith.
He had them sent out for Full Hydrostatic Destructive Testing!!!!!!!!!
 
This is a reprint his post

I machine alot of things. I constantly get request's for Titanium tubes but have not been real keen on making them. I dabbled with a couple and did some tests of my own and was able to hyro them to 12,500 psi before my pump maxed out. With more people asking for them I decided to sent some out for testing at Maxbar in Houston. They are a lab that does pressure testing and have the capabilty to pressure test to 300,000 psi and have the proper equipment to read the exact pressure.
Here is what you have to work with:
End cap threads
1.387-24 thread
pitch dia of 1.357
1" of thread engagement
1/8 npt fill port. Same as the quick fill
One set of endcaps are 7075 T6 Aluminum and one set is 316 stainless to see which fails.
The Titanium is from Titanium Joe and is 1.500 dia .087 wall(actually comes in at .084 wall) and is 3al-2.5v Cold Worked Stress Relieved (CWSR) Seamless. Here is the properties
http://www.titaniumjoe.com/grade9Data.htm
My O-rings are placed between the pressure and the threads.
Here is the test pieces sent to Maxbar. One set of 7075 end cap and one set 316 stainless. Which failed first and why? 

Now for the results.....

The tube wall failed right at the end of the thread at 17,448 psi. Both the aluminum and Stainless end caps held the thread shear as did the Ti tube. The tube wall bulged and the O-rings held until the failure at the end of the thread. The wall thickness at this point would be .0565"
They both failed within 2psi of eachother. I was a little concerned the thread of either the end cap or the 1/8 npt would fail first. I was just not sure of the calculations and needed something to prove them.
Here is some pics.

 
So with Chip's invaluable contribution to this area..
This Validates my conclusion I had on this subject...
The weakest link in the Titanium Tube is.....
The area you turn for the internal threads!!!

Also, here is the actual test results that Chip received from the testing company.


This is some great information from Chip!!
Thanks for all he has done for the sport!!!!

Stuart

[KevG]

Very interesting read.i love stuff like that.
KevG

[KCE]

A very interesting read indeed.
Chip Smith like so many of you guys are a valuable source of knowledge and without you guys the world about the rapid would not be the same.
Most if not all of them would be in cupboards or cabinets unusable.
Some of you guys have taken the rapid in to the next world with your ideas and concepts and I for one am very grateful to still be a proud owner of a rapid or two.