.25 build specs

[Airsnipe]

You can have your Titanium tube Cerakoted.....

Ya, I have been looking into cerekote, duracoat, aluma-hyde... Seems like Cerekote is the way to go. Anyone have experience with any of these and would like to share opinions?

[Bill G]

Thanks Bob, I was planning on going with 75%-80% of bore based on some of your other posts I have read. This was exactly the confirmation and push I needed to get some stuff done. 

Bill, it's a ground up build. I'm using a 1.5"OD titanium tube so a Marauder valve is not going to work out. I also don't think I'm going to pin the valve. I don't like the design requirements to pin @ 1.5"OD forces. I know its doable but threading sounds much easier to accomplish all the safety factors I want and the design I want. That and I have a lathe that has a through hole that will fit the tube. The valve and end cap/fill adapter will be 7075.

One thing I'm stuck on is how I'm going to make the Ti tube black. Doesn't seem like you can anodize Ti black so maybe powder coating.

 

What are your specs for the Ti tube?  Are you going to thread it or use the screw/pinned method?

[Airsnipe]

I am using 3al-2.5v (105k yield) 1.5 OD .087 wall. Both ends will be threaded.

[Rizen 1]

I personally like the cerakote.... Both my Extreme rifles have all the parts cerakoted and I am very pleased with the durability..

Also, here is something about the tube you are using that you may find useful..http://www.airgunadvice.net/viewtopic.php?t=16452&highlight=pressure+test

[Airgun.Sniper]

 You guys always have bright ideas which is pretty cool for sure

 Cheers

 Jay

[rsterne]

Interesting test of the TI tube.... looks like the ultimate failure was a tensile failure of the tube wall where the thread stopped, an area that is only subject to pressure once the O-ring lest go.... up until then it is in pure tension.... Judging by the big bulge in the wall of the tube, I would say that area is NOT an area of concern, however, and here is why.... JMO of course....

It seems obvious to me that the first thing that happened is that the tube wall started to expand, because the hoop stress exceeded the yield strength of the tube wall.... Once that expansion reached the O-ring, which may have happened rather rapidly, the O-ring ceased to seal, and the pressure was then allowed to reach the end of the thread root.... That area was strong enough to resist the end force on the plug (pure tensile), but once the hoop stress was added, it failed immediately and catastrophically.... The good news here is that the tube bulged before it failed.... If it hadn't bulged, the O-ring would have still sealed, and the thinned area at the thread root would likely not have failed.... With 1" of thread engagement, I am not surprised that neither end plug had a problem, in fact you could probably remove them by hand after the test and they would have looked perfect....

Bob

[Airsnipe]

This is a great test.

Now I wonder how this failure would have happened if there would have been some holes in the tube between the o-ring and the threaded section like Bob had suggested earlier? As long as the holes where large enough the vent the pressure quick enough and did not cause the weak link by weakening the tube, I would guess the tube would have dumped the pressure without such a catastrophic failure (tube separation). 

[Airsnipe]

I personally like the cerakote.... Both my Extreme rifles have all the parts cerakoted and I am very pleased with the durability..

Also, here is something about the tube you are using that you may find useful..http://www.airgunadvice.net/viewtopic.php?t=16452&highlight=pressure+test

Did you do the cerakote yourself or have it done?

[lloyd-ss]

This is a great test.

Now I wonder how this failure would have happened if there would have been some holes in the tube between the o-ring and the threaded section like Bob had suggested earlier? As long as the holes where large enough the vent the pressure quick enough and did not cause the weak link by weakening the tube, I would guess the tube would have dumped the pressure without such a catastrophic failure (tube separation). 

Chip Smith (who made the tube and commissioned the test) makes lots of Ti tubes and has the knowledge and experience that go along with that.  Designing a weak link into your system that will give you a soft failure is a good idea, especially if there is the potential of over-pressurizing a particular part in the system.
Lloyd

[lloyd-ss]

For the Cerakote finish, I like it ok, but I have a local source that does a very nice job with polyester powder coat, which I really love.   The particular product he uses for my stuff is VERY tough and you can drill and machine a finished part without chipping or separation.  Using proper care, I can even chuck parts in a lathe right on the powder coat with no marring  of the finish.  One thing to be aware of is the buildup of the powdercoat (and Cerakote, too) onto the surfaces.  Like if you are making a close slip-fit band around a tube and both parts get powdercoated all over and you have .003 buildup per surface, that means you need a total clearance of .012 so that the parts will fit back together.  And different shops will have different thicknesses.
Another thing about powder coat is that it builds up a little extra on SHARP outside corners.  So you need to give all outside corners a noticable edge break or radius to avoid assembly or appearance problems.  Lessons learned, LOL. 

[moorepower]

You can anodize ti. I have some of the same tubing, and my plan is to use 7075 threaded ends, but one end will be similar to a Hatsan, with the valve being made using an end cap. As long as you're using a block for the hammer it would be the easiest and safest way that I can think of to do it.

[Airsnipe]

You can anodize ti. I have some of the same tubing, and my plan is to use 7075 threaded ends, but one end will be similar to a Hatsan, with the valve being made using an end cap. As long as you're using a block for the hammer it would be the easiest and safest way that I can think of to do it.

I don't think you can anodize it black.

[moorepower]

You're right, it's more of a very dark purple.