Author Topic: XS60C PCP Repeater project (Read 455915 times))

stalwart · « **Reply #700 on:** December 05, 2014, 06:17:29 AM »

More pressure to build a .30...

I guess the .50 cal will have to wait.

Some cool parts will be here soon. Ninja...

RHytonen · « **Reply #701 on:** December 05, 2014, 07:00:39 PM »

Quote from: stalwart on December 05, 2014, 06:17:29 AM

More pressure to build a .30...

I guess the .50 cal will have to wait.

Some cool parts will be here soon. Ninja...

Add my pressure on that .30...

Rod

stalwart · « **Reply #702 on:** December 05, 2014, 07:44:55 PM »

Quote from: rsterne on November 13, 2014, 12:34:12 AM

Just as an aside.... I looked up the tap drill size for a 13/16-16 tpi thread and it looks like 19mm or 3/4".... Shouldn't that start right into a 7/8" OD x 0.065" wall tube (0.745" ID).... The OD is still 0.8125 regardless of the pitch, so why couldn't you use a thread that coarse on an end plug?.... Anybody?.... The minor diameter of that thread is 0.745"....

Bob

I've considered all options, and I'm thinking this is a good one for my Grizzly. I want max plenum. How far would I have to go in?

Guys, Bob is going for a nice reverse set up, and I'm trying for more of a "brush gun". Bob has his figured out... I do not. Comedy ensues...

rsterne · « **Reply #703 on:** December 05, 2014, 10:13:56 PM »

Without doing the math, 3 threads is probably enough but I'd never do that.... certainly 1/2" of engagement would be plenty.... The weak point will be the threaded assembly trying to pull the tube apart right at the end of the threads where the wall thickness is the tube thickness minus the thread depth.... Since the tube is 0.875" OD and the 13/16" threads are 0.813" OD, the remaining wall is 0.031" thick, so the area is PI x (0.813+0.875)/2 x 0.031 = 0.082 sq.in..... If the tensile strength of the tube is 70K and the yield point is 52K (1021 steel) the yield point is 4264 lbs.... At 3000 psi on a 0.745" plug the end force is 1307 lbs. so the safety margin to yield is 3.26:1.... If you use CrMoly with a yield strength of 63K, that increases to nearly 4:1.... The safety margin to failure is greater, of course....

Bob

stalwart · « **Reply #704 on:** December 06, 2014, 01:34:13 PM »

Cool. Thanks, man.

I'm sure I'm not the only one here who appreciates how completely you answer questions.

tominMPLS · « **Reply #705 on:** December 08, 2014, 01:58:56 PM »

That is the absolute truth! Bob's posts are not only thorough, his designs brilliant, but his explanations make you realize that perhaps a builder is not putting enough thought into the safety of a design. Designing a project is great when everything fits and functions as you envisioned it should, but is that design as safe as you can possibly make it? I think (myself included, until now) safety is too easily overlooked in the "rush to create" the newest coolest and best rifle/pistol/gizmo ever. I cannot thank him enough for making me realize this important fact.

Thank you Sir! You are greatly appreciated!

Tom

stalwart · « **Reply #706 on:** December 08, 2014, 04:57:38 PM »

Look what Tim (Mac1) sent! Regged to 2K.

Based on Bob's calcs, we are going to end up with a couple .30 repeaters with enough shots per fill to mean it.

rsterne · « **Reply #707 on:** December 08, 2014, 05:56:08 PM »

SWEET !!!

I'm gettin' antsy.... *grin*....

Bob

rsterne · « **Reply #708 on:** December 08, 2014, 07:14:08 PM »

I've been plagued with a leak in my sons's FD-PCP since new.... I tried everything to get it to seal to no avail.... One serious problem was a deep lengthwise scratch in the receiver, and when I found that I was sure that was the problem.... I sanded out the inside of the receiver where the O-ring sits, leaving the paint in the scratch, but it still leaked.... I wasn't happy with the OEM seal on the end of the threaded tube which is a rather hard, proprietary item that is pinched between the end of the tube and the front of the valve, and "maybe" expanded outwards to seal, or maybe not.... If you tighten the tube too much, it pops inwards and you can't even fill the gun it leaks so badly.... I had tried O-rings, 70D, 90D, square in cross section, quad-seals, but they all popped out on installation....

I came up with the idea of making a thin insert that I could put inside the tube, with a shoulder to keep the OEM seal from collapsing inwards, and that at least allowed me to tighten the tube in as tight as I could by hand without it popping inside the tube.... It STILL wouldn't seal.... Then this morning I awoke with the idea of using the seal holder insert with a standard 90D #115 O-ring.... I reasoned that the insert would keep the O-ring from popping inwards, and when I tightened the tube against it, it would have to expand outward to seal that all important gap between the receiver and the outside of the tube, where the threads are.... FINALLY, I got a seal.... Here are the parts....

Seal holder with O-ring

Seal holder with OEM seal in place (didn't work for me, might for you)

The installation that FINALLY sealed up....

The tube shown isn't the threaded one from the FD-PCP, but is the same ID and OD.... The brass insert is glued into the end of the tube with a drop of crazy glue.... There is no load on it, you just don't want it to slide out of the way.... The shoulder on the insert is flush with the end of the tube, and the part that fits into the O-ring is 0.080" long and 11/16" OD.... The insert is 5/8" ID and the OD is a slide fit inside the tube, about 0.740" works fine, then glued in with the 11/16" portion proud of the end of the threaded tube.... After installing the valve, you slide the lubed O-ring down to sit against the shoulder in the receiver.... Thread the tube in, and the short, 11/16" OD part of the insert goes inside the O-ring and the end of the tube tightens against the O-ring.... It can't pop inwards because the insert prevents that.... so it expands outwards against the receiver, pinched between the end of the tube and the receiver....

One other thing, make sure that the end of the tube is smooth and square.... You don't want it to slice up the O-ring.... HAND TIGHT IS ALL YOU NEED....

Bob

stalwart · « **Reply #709 on:** December 09, 2014, 03:12:52 PM »

Well done, Bob. Thanks for putting it here.

For all... a teaser:

RMM · « **Reply #710 on:** December 09, 2014, 04:01:30 PM »

You two, Bob and Eric, never cease to amaze me.

I've got not much farther than this but Stalwart 2K .30, meet Mike's 1.5K .22.

P.S. Mine is just going to be a brush gun.

rsterne · « **Reply #711 on:** December 09, 2014, 11:15:02 PM »

OOoooooooooooo.... getting closer.... *grin*.... I really like the looks of that with the 22CI tank, looks MEAN.... like a Grizzly....

Bob

stalwart · « **Reply #712 on:** December 10, 2014, 11:39:56 PM »

It's going to be a fun little rig, Mike. You going for shot count, or zip?

Quote from: rsterne on December 09, 2014, 11:15:02 PM

OOoooooooooooo.... getting closer.... *grin*.... I really like the looks of that with the 22CI tank, looks MEAN.... like a Grizzly....

Bob

Very close, actually... and headed North, soon.

I love this place...

RMM · « **Reply #713 on:** December 11, 2014, 06:31:13 PM »

Quote from: stalwart on December 10, 2014, 11:39:56 PM

It's going to be a fun little rig, Mike. You going for shot count, or zip?

I love this place...

I'm seeing the importance of FPE for hunting , with accuracy of course, so zip it is. I'm still in the novice mode, you and Bob are light years ahead of me, but I'm having a ball with this stuff, including my mistakes.

I love this place also...

RMM · « **Reply #714 on:** December 13, 2014, 11:17:39 AM »

I'm using an rsterene Maxi valve in my Bobcat and it can be removed out the rear of the receiver so does anyone see any reason the tube to receiver threads can't be permanently epoxied or red Loctited?

Or let's go one step further and leave out the flat o-ring and let the epoxy or red Locktite be the seal??

rsterne · « **Reply #715 on:** December 13, 2014, 12:59:49 PM »

Other than that you are pulling the valve O-rings out past slots, which tend to be hard on them, I see no reason.... There is actually a purple Loctite made, I believe, for sealing Hydraulic fittings that might be just the ticket.... JB Weld should work as well, of course.... Mind you, if you get a leak, you'll never get it apart to fix it, either....

Bob

RMM · « **Reply #716 on:** December 13, 2014, 01:52:49 PM »

Thanks Bob and I'm still putting some thought to the permanent tube to receiver idea, it was your tube leak problem that got me thinking. I'm just playing with my Bobcat and If I decide to just screw in the tube I will be doing your 0-ring trick, oh and thanks by the way.

My other two 60's will be Stalwart 3Ks so I'm setup just right with those.

Still having fun in IL

tominMPLS · « **Reply #717 on:** January 04, 2015, 02:36:47 PM »

Hey Eric, anything new going on with the project? Did everyone go to the Bahama's?

And Bob, thanks for sending all that Canadian below zero weather down here for us Minnesota people to enjoy! LOL!

Tom

rsterne · « **Reply #718 on:** January 04, 2015, 03:01:24 PM »

Waiting for parts to arrive here.... from two sources....

Bob

ali · « **Reply #719 on:** January 05, 2015, 11:25:46 AM »

Hi. Does anyone knows how to calculate the tube's tensile strength having allen screws in shear like the US FT PCP airgun front plug?
I had observed that the screws here are not in the same axis - i think 3 screws are in the front and maybe 2 screws somewhat at the back.

Based on the looks of it, the tube strength is increased. Am I right?

Thank you to our advertisers!

XS60C PCP Repeater project

Author Topic: XS60C PCP Repeater project (Read 455915 times))