4500 psi main tube?

[Blutroop]

So who’s got em and what are the specs? Are they all titanium or are there any aluminum main tubes holding up to 4500?

[screwwork]

Jeremy
Which gun, there are so many brands out there?

[rsterne]

Exactly.... The pressure rating depends on the material, OD and wall thickness.... Increasing the wall thickness will increase the MSWP.... but of course your valve may no longer fit.... 

Bob

[Blutroop]

I’m curious to know what’s out there. I would love to have a prod/disco size tube in titanium but am doing some swapping for a .408 barrel so getting into big bore a lot sooner than planned. I don’t really know about any guns that aren’t Benjamin/crosman yet.

[rsterne]

A Disco sized reservoir is too small for a .408 cal, in my opinion.... Ideally you should be looking at a reservoir volume of 1cc per FPE or larger to get any kind of shot count at all, even in a big bore.... Most small bore PCPs have a reservoir of 5cc per FPE.... Big bores not so, as the reservoir would be huge....

Bob

[Rob M]

following

[Blutroop]

Ok how about a marauder tube. I talked to don cothran years ago and he was working on titanium tubes. I don’t want to bug him now after hearing about his son. How thick would a marauder sized tube have to be if aluminum? Are there manufacturers out there with titanium tubes already?

[Rob M]

Ok how about a marauder tube. I talked to don cothran years ago and he was working on titanium tubes. I don’t want to bug him now after hearing about his son. How thick would a marauder sized tube have to be if aluminum? Are there manufacturers out there with titanium tubes already?

in 2024 aluminum i believe travis already made a batch of mrod tubes..No thicker than the steel ones IIRC>.
The best ive seen of titanium tubes was chip smith.. He was a forum member many years ago who built bench rest guns from scratch.. One of his tubes , while being rather large diamter ( 1.75 as i recall) was tested to failure at over 17,000 psi.. Which is over a 4 to1 safety ratio for 4000 psi fills.

[Rob M]

theres a bunch of limitations , which have been tested when it comes to tube diamter and pressure..
Number one is , compressing air above 4500 psi is a PITA , as the heat gets extreme and melts seals , the HP required gets high also.
2 , as tubes grow in diameter, the forces on these tubes GOES way up , its not exponential , but the numbers get staggering fast.. SO then you have to secure a valve facing 8000 LBS of pressure pushing it out torward ur face.. Not a good scenario..it all gets complex, and the people building stuff for a long time have thought about these very things, and done the math.. SO has the DOT , and hence they regulate certain pressure vessels.( most actually )
Tanks are a good solution , be it a small one , or a large one.. BY design , theyre ends are part of the cylinder itself. ( as opposed to a pcp tube where thats not true )
again , its all complicated and pcp failures can be deadly..

[Rob M]

this guy took a valve into leg a few yrs ago



lucky it didnt hit his femoral

[Blutroop]

Hey Rob m, thanks for the replies. I watched that video to the end even though I lost interest when they said hi-pac and that’s a pretty big hole in the leg!
I’ve seen Jsar aluminum tubes. I believe there only rated for 3000 and the last few years they’ve been too busy with their raptors to make anything else.
I have had some training and experience with hydraulics so I am aware of the decrease in pressure handling with the increase in pipe diameter. I haven’t a clue how to turn that knowledge into actual figures like people like Bob seem to do effortlessly.
While we are talking about pressures I found some 45g co2 cartridges sold in pet stores that have a test pressure of 4000 and burst of 8100. After seeing Bob’s millennium pumper and your little mad max pistol I can’t get those cartridges out of my mind. Obviously they are not big enough to work for a .408 build but I might be able to make a small little .172 or 177 carbine pumper/pcp.
Hey what thread size are Benjamin gauge ports?

[rsterne]

CO2 cartridges have a MSWP of 1800 psi.... The 8100 psi burst insures a 4:1 safety margin....

A 3Al-2.5V CWSR Titanium tube of the same dimensions as the MRod factory tube will have about the same safety margin at 4500 psi as the stock tube does at 3000.... HOWEVER, the valve securing screws and the threaded fill plug won't be any stronger.... I think they are strong enough, but you should ask Lloyd for confirmation....

Bob

[Blutroop]

Thanks Bob. I’ve also been thinking about making a valve that screwed in like the fill plug but that’s assuming that the threaded side can hold up to more pressure than the side full of screw holes.
The prints you sent me of the co2 cartridge you used on the millennium pumper show a test pressure of 3650. I’m I being naive to think that this one with a test pressure of 4000 can hold a little more? 

[rsterne]

The test pressure is irrelevant.... Pressure vessels built to ASME specs must have a minimum 3.5:1 safety margin to burst.... That 16 gr. CO2 was (over) 500 bar (7250 psi) to burst.... If you are confident that the ones you have found are 8100 psi to burst, you can use about 2300 psi for a MSWP....

Bob

[PakProtector]

Bob, recall that even 'valve screws' is a variable quantity vs working pressure. The short cap screws are loaded differently from the standard type( as employed OE in the Marauder ). For a given screw quality, I recall that the OE form factor stresses that joint less. But echoing your point, check with the Lloyd who has actually pushed samples to failure.
cheers,
Douglas

[Blutroop]

If I remember correctly when he tested to failure the break would be on the valve side. If the screw in fill nozzle Is capable of higher pressure then I could thread a valve so that it’s no longer the weak link. I’m trying to make friends with a local that tests and rebuilds fire extinguishers. If I get any neccissary fittings I’m sure I can test em.

[PakProtector]

If I remember correctly when he tested to failure the break would be on the valve side. If the screw in fill nozzle Is capable of higher pressure then I could thread a valve so that it’s no longer the weak link. I’m trying to make friends with a local that tests and rebuilds fire extinguishers. If I get any neccissary fittings I’m sure I can test em.

Exactly, which is one of the reasons the Bottle adapter I designed for the Marauder screwed into the air tube with 1.125-20 threads, just like that fill cap did. Three screws as pins was not as strong. And I did it out of 7075... so y'all can tell the ones that were mine; they are bright silver, instead of anodized 6061.
cheers,
Douglas

[antithesis]

Ok how about a marauder tube. I talked to don cothran years ago and he was working on titanium tubes. I don’t want to bug him now after hearing about his son. How thick would a marauder sized tube have to be if aluminum? Are there manufacturers out there with titanium tubes already?

What happened with Don's kid?