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All Springer/NP/PCP Air Gun Discussion General > Engineering- Research & Development

Seamless tubing for air reservoir ?

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sperho:

--- Quote from: AmBraCol on March 08, 2013, 02:15:06 PM ---
--- Quote from: sperho on March 08, 2013, 01:56:42 PM ---Keep in mind your threaded couplings/endcaps will likely be the weak points...

--- End quote ---

That's what I'm thinking. There should be enough "beef" around these points to ensure safe use to 3,000 psi or so. 

--- End quote ---

Beef and # of threads making good contact...

lloyd-ss:

--- Quote from: AmBraCol on March 08, 2013, 01:54:19 PM ---Thank you, sir!  That info is quite gratifying.  I'm still not sure how to approach the project, but that kind of safety margin should cover for many beginner mistakes as far as the air reservoir / pump tube goes.  It will make for one heavy piece, but somehow anything I make tends to end up that way.  There was the time that I made up a homebrew muzzle loader, years ago, and used a piece of extremely dense brazilian hardwood for the stock.  It took two men and a boy to carry it but recoil was practically non-existent!

--- End quote ---

I believe you are going after what is called in the engineering world, a "Robust design", which translates into too darn heavy to lift, LOL.
A53 and A106 are 2 different specs for similar kinds of welded/weldable steel pipe.  The Grade B in both of them has a yield spec of 35ksi, and sampling testing of hydrostatic to 60% of yield, or up to 2,600 psi, whichever is less.  In this case the 2600 psi is definitely the lesser.

Your pipe weighs over 3 lbs/ft, and seems to be up to the task, but  I am curious why you really want to use it?  You can get A513 Ty5 DOM steel tubing very inexpensively, and in small quantities, which has a yield twice as high at 72ksi and a smooth I.D. and eliminate probably 3/4 of the weight. You can choose the thickness you need for the job.  Just a thought.
Lloyd-ss
 

AmBraCol:

--- Quote from: lloyd-ss on March 09, 2013, 09:45:57 AM ---
--- Quote from: AmBraCol on March 08, 2013, 01:54:19 PM ---Thank you, sir!  That info is quite gratifying.  I'm still not sure how to approach the project, but that kind of safety margin should cover for many beginner mistakes as far as the air reservoir / pump tube goes.  It will make for one heavy piece, but somehow anything I make tends to end up that way.  There was the time that I made up a homebrew muzzle loader, years ago, and used a piece of extremely dense brazilian hardwood for the stock.  It took two men and a boy to carry it but recoil was practically non-existent!

--- End quote ---

I believe you are going after what is called in the engineering world, a "Robust design", which translates into too darn heavy to lift, LOL.
A53 and A106 are 2 different specs for similar kinds of welded/weldable steel pipe.  The Grade B in both of them has a yield spec of 35ksi, and sampling testing of hydrostatic to 60% of yield, or up to 2,600 psi, whichever is less.  In this case the 2600 psi is definitely the lesser.

Your pipe weighs over 3 lbs/ft, and seems to be up to the task, but  I am curious why you really want to use it?  You can get A513 Ty5 DOM steel tubing very inexpensively, and in small quantities, which has a yield twice as high at 72ksi and a smooth I.D. and eliminate probably 3/4 of the weight. You can choose the thickness you need for the job.  Just a thought.
Lloyd-ss

--- End quote ---

Well, locally there's only one supplier of seamless tubing that I've been able to locate.  The smallest piece they sell is a half bar - about 3 meters long.  A while back I picked up this tube for an 8 bore BP shotgun project I'm also kicking around.  Since I grew up around brazilian muzzle loaders made with seamed curtain rod for barrels I figured this heavy walled seamless tubing should be up to the task of containing the combustion gasses and directing the payload in the general direction desired.  Since a short barreled smoothbore doesn't take that much off the end of a 3 meter section of pipe I'm left with enough to do all kinds of things with.  :-D  I may end up going back for a thinner walled section, in the meantime I'm playing around with options to use what's on hand.  I'll put up a sketch of what I have in mind for the air reservoir once I get it done.  It'll be a 'range rifle', not a hunting piece that's for sure.  Making do with whatcha got has been the story of my life, rarely does one seem to acquire ideal combinations of components when one lives in an area where one's interests are not shared by many in the general population.

Thanks for the info.  It looks like my instinct for the serviceability of the tube for the original intended purpose was spot on.  A moderate charge of BP under a wad and shot should not come near the pressures you indicate, assuming proper loading techniques and no obstructions in the barrel.  I'll thoroughly proof it before final build to ensure things work like expected, of course.  In the meantime I continue my pneumatic project design.  It'll be heavy, no doubt, but should prove a load of fun at the rifle club if I ever manage to pull off the build.

lloyd-ss:
That makes more sense now.  I understand about making do with what you have on hand. If you did want to reduce the weight of the tube you could always turn the O.D. to reduce the wall thickness. Good luck on your project!
Lloyd-ss

LD9125:
Found this post when looking at wall size for air reservoirs and no one gave the answer for what 8ch160 is so ill necro it.

MLES  CS  8CH160  1"5**  81564  ASTM  A106  /  A53 GR  B  /AP/  5L  GR  B

It isn't an 8

The marking is sch 160 and with the dimensions given  it's seamless schedule 160 1" pipe and not tubing

The mles is either
the end of smles for seamless
or a shortened company or trade name ti indicate who made it

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