Edgun air tubes
Anyone know what material (7075-T6?) and the max pressure rating is on Eds tubes? Just curious as to the specs. I know he prefers to use socket head cap screws vs threads which I understand is a stronger solution.
Thanks
DT
All Replies
Sorry if I missed it but what are you filling the Leshiy too and is the tube made out of Duralumin too? Is it basically the same as a Lelya tube but a bit longer?
Thanks
DT
Yes, that is the same.
Ed
Ed,
Sorry if I missed it but what are you filling the Leshiy too and is the tube made out of Duralumin too? Is it basically the same as a Lelya tube but a bit longer?
Thanks
DT
Btw, does your country have the equivalent of 7075 aluminum? Any reason you chose 2024 over 7075? Cost or performance maybe? Does your tubes come extruded in 3.2mm thickness or do you machine it from a solid rod?
I have yet to find a supplier of 7075 t6 alluminum tube in USA never mind russia……
I found photo of 2006 at my computer of how it was 🙂 So old and funny how it was 10 years ago.
So, you can see the gauge and the reservoir testing:
Here is can see the maximum damage of the reservoir. As you see the tube is OK but the wholes for the screw head became ellipse out of circle. That was the only damage. Once, when we reached the pressure of 650 bar the plug moved back in those ellipce wholes and O-ring reached the whole and the water just went out and the pressure dropped down. The same could be with the air, you will get just blast of air out of that whole due to the O-ring broken and that’s it.
Design wise, Ed’s reservoir with the ends held on by bolts is very smart. I’m curious what metal are the retaining bolts made of? Unlike threaded ends where the material is thinner due to making of the threads is where most fail under testing that I’ve read about. If I were to design an airgun, I’d use the same bolt technique. I must say though Ed, your exposed fill port idea sucks. The Cricket has a better design except for the fact you can’t prop it open. I think your newest .30 cal Matador has a newer covered fill port design? Hopefully your new line of guns also incorporates this.
Btw, does your country have the equivalent of 7075 aluminum? Any reason you chose 2024 over 7075? Cost or performance maybe? Does your tubes come extruded in 3.2mm thickness or do you machine it from a solid rod?
Ed,
Just curious. I thought it had some advantages in fatigue strength and weight since you could get away with a thinner wall for more air volume. I see now that the aluminum you are using is very robust and well tested. No worries.
Dan
What are your thoughts on Titanium as a tube material?
Thanks
Dan
It is twice heavier then duralumin with the same or worse mechanical characteristics. Why?
Ed,
What are your thoughts on Titanium as a tube material?
Thanks
Dan
Good stuff guys. Thanks again for the info and contributing to this discussion.
I think my questions have been answered and then some!
DT
Ed,
Thanks for the reference. That’s a good durability test.
-x356b
That is the reason I use D16T for the reservoirs (in fact all details of EDguns are made of D16T). Just an example. We use the part of the tube of the reservoir for adjusting the regulators. It looks this way, the front plug is taken off, the regulator is put inside, the front plug is taken in, fill the pressure, check the regulator. Take it off, readjust, repeat the procedure and it can be few times. We have few tools like that, they work for years. It means that all the regulators which we use for guns pass through these few tools for years. Thousands regulators, dozen and dozen thousands cycling of fill in and release out of air. Hundred thousand cycles. You can see them. They are still working…
I’ll concur with Veer and Dan. Non-ideal properties of gasses at high pressure can explain the apparent non-scalability of shot count with pressure. When the pressure goes very high the underlying assumptions in PV = mRT are no longer correct. (The assumptions being that the volume of the gas is mostly empty space and that there are no attractive forces between gas molecules.)
The van der Waals approximation that Veer references is a good way to understand what’s going on, but is not used so much in anymore in engineering calculations. There are more accurate models. A recent NIST paper gives some idea of the state of the art.
http://www.nist.gov/data/PDFfiles/jpcrd581.pdf
What all of this says is that the shot count deficiency at high pressure is not a regulator problem, it is a property of high pressure air. Unfortunately, air stops behaving as a nice big spring when the pressure goes high enough.
Regarding Dan’s question that started this discussion, Ed has shown that the yield strength of the airtube/end fitting system is around 650 bar. If I remember correctly, Luxfer states that its tanks will not fail below 5/3 of working pressure. So the airtube system has a good safety margin compared to diving cylinders.
Another failure mode to consider is cyclic fatigue failure. This is different than the yield strength failure. In cyclic fatigue, repeated cycling of the load (tank pressure) at levels far below the yield strength will cause a failure. I’d be a little surprised if cyclic fatigue is a problem on airgun tanks, given the low cycle count (number of refills) a tank undergoes. (Has anyone seen references on this?)
-x356b
Regards, Robert.
I think this explains it but I am a little rusty on my physics! :sadn:
DT
Dan
I fill both Lelya and Veles up to 240 bar.
and the matador ??????
http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/waal.html
Regards, Robert.
- You must be logged in to reply to this topic.
Ed i sent you a msg, can you confirm you got it? thank you.