Author Topic: XS60C PCP Repeater project (Read 456134 times))

rsterne · « **Reply #120 on:** February 21, 2014, 02:08:07 PM »

Now that I actually HAVE my FD-PCP, I am somewhat doubtful if you can pull off an 8-shot string within a 4% ES in .25 cal, with the extra power, and hence extra air required.... I'm only getting 9 shots with 4% ES with 15.9 gr. JSBs at 27.5 FPE, from 1500 psi down to 1100.... The gun breathes really well, which is great for producing power, but that narrows up the shot string for a given ES.... My recently converted .25 cal Disco is getting 8-9 shots at just under 50 FPE with a 23.8" LW barrel.... and that is with a 2000 psi fill, refilling at 1200, and a larger reservoir than the 60C....

Bob

avator · « **Reply #121 on:** February 21, 2014, 05:40:04 PM »

Bob;
can u plese tell me how you are determining that you have 1100 psi remaining, have you added a guage somewhere and if so, where and how?

Thanks

toine · « **Reply #122 on:** February 21, 2014, 07:12:38 PM »

Quote from: avator on February 21, 2014, 05:40:04 PM

Bob;
can u plese tell me how you are determining that you have 1100 psi remaining, have you added a guage somewhere and if so, where and how?

Thanks

Bill -

I don't know if this is what Bob has done, or if he is just using measurements from when he refills.

http://www.gatewaytoairguns.org/GTA/index.php?topic=61955.0

stalwart · « **Reply #123 on:** February 21, 2014, 09:09:43 PM »

Quote from: rsterne on February 21, 2014, 02:08:07 PM

Now that I actually HAVE my FD-PCP...
Bob

'Bout time, eh?? Was it the border thing that took so long?

What do you think about the bolt face thing? There's plenty, right?

rsterne · « **Reply #124 on:** February 21, 2014, 10:03:46 PM »

I was just noting the pressure when the gauge on the filling tank slowed up, so it's not super accurate.... My new gauge will help....

The only thing I have noticed about the bolt so far is that the probe is wayyyyyyyy longer than it need to be to load a pellet ahead of the barrel port.... However, the chamber is also VERY deep, if you seat a pellet until the skirt just touches the end of the chamber, it's about 1/8" past the barrel port....

Are you shortening the barrels, moving the shoulder, and redrilling the port?.... or are you just removing the loading tray....

Bob

stalwart · « **Reply #125 on:** February 21, 2014, 10:22:37 PM »

I shorten, then refit properly. Lot of slop in the stock set up.

Kailua · « **Reply #126 on:** February 21, 2014, 11:09:02 PM »

I may be wrong and one should talk to Mike. But Mike's recommendation on 1500 psi is based on operation with the stock hammer and spring. The gun may be able to hold a lot more PSI.

stalwart · « **Reply #127 on:** February 21, 2014, 11:20:48 PM »

Quote from: Kailua on February 21, 2014, 11:09:02 PM

I may be wrong and one should talk to Mike. But Mike's recommendation on 1500 psi is based on operation with the stock hammer and spring. The gun may be able to hold a lot more PSI.

That's my understanding, too.

Al (airgun-warriors) said he'd go for my suggestion, and blow one up. I offered to chip in, I think it's vital data. Adding frills is fun, but I'd like some hard (safe) numbers. I guess we'll see if he's serious, soon. He has access to proper testing, I don't... or I'd do it. I'm in these for the long haul.

I plan to double up all mounting points before attempting anything, but have decided to try a simple .25 @ 1500 (or so...

) to see what kind of a base it makes.

Big Bore Bart · « **Reply #128 on:** February 21, 2014, 11:32:44 PM »

Mike did say ~~the~~ a tube had been hydro'd to 4k psi, and was rated to 6k.

Found it. It's in this thread. http://www.gatewaytoairguns.org/GTA/index.php?topic=57905.0

rsterne · « **Reply #129 on:** February 22, 2014, 12:32:00 AM »

Yes, I'm sure that is probably true.... but is that before or after it was threaded to remove about half the wall thickness?.... We still don't know what material it is.... I just ran the numbers on mine, they are in this thread.... http://www.gatewaytoairguns.org/GTA/index.php?topic=62302.0

The big problem, as I see it, is the valve mounting screws.... Assuming they are just mild steel, the safety margin is only 1.8:1 at 1500 psi....

Bob

Kailua · « **Reply #130 on:** February 22, 2014, 01:05:41 AM »

Quote from: rsterne on February 22, 2014, 12:32:00 AM

Yes, I'm sure that is probably true.... but is that before or after it was threaded to remove about half the wall thickness?.... We still don't know what material it is.... I just ran the numbers on mine, they are in this thread.... http://www.gatewaytoairguns.org/GTA/index.php?topic=62302.0

The big problem, as I see it, is the valve mounting screws.... Assuming they are just mild steel, the safety margin is only 1.8:1 at 1500 psi....

Bob

Does adding screws to maybe the sides of the valve help the chances of being safe at a higher pressure?

stalwart · « **Reply #131 on:** February 22, 2014, 05:57:27 PM »

Does anyone have any suggestions for stripping the coatings on these? The stuff is impressively resistant to Aircraft Remover. It's working, but is taking a lot of effort in places (nooks and crannies), and more time than I thought it would.

I'm prepping for Teflon bearing powder coat, so there can be no remnants.

TIA

rsterne · « **Reply #132 on:** February 22, 2014, 10:19:51 PM »

Adding screws would eliminate that problem, but using 2000 psi would then push the threaded portion of the tube to less than a 2:1 safety margin (assuming mild steel tubing), and then fatigue becomes an issue.... The solution to that would be CrMoly tubing, or a thicker wall tube (and hence more weight and less air volume)....

It's a converted CO2 gun, guys.... Protect it with a 1.8 K burst disc, which limits you to 1500 psi regulated.... or flll it (carefully) to 1500 psi.... Anything more than that, do the math on ALL the components and make SURE you know what you're doing.... same thing as if you were working on a QB/AR.... There is a reason it's only $100....

Bob

stalwart · « **Reply #133 on:** February 24, 2014, 03:12:52 AM »

Guys, is there any reason why a tube couldn't be made that would extend into the receiver, around a reduced OD valve, and basically act as the entire pressure container? The receiver could easily be bored out a bit, and if the tube was bonded to it, it would only have to do what a typical breech does.

I'm trying to figure out how to get both more volume and pressure. I have an idea that would (maybe) allow a tank block offset enough to work with the close tolerances the integrated receiver creates, and take the worry out of having that threaded joint.

Crazy?

Edit: It's going to be easier than I thought. There is plenty of room to set 7/8" (3/4" ID) DOM steel tube into the receiver without cutting it down. I've read here this stuff is good for 6K (and I have a bunch of it), so I should have quite a margin to work with... and stock valves will slide right in.

Started a mandrel, but will need a longer boring bar. It's always something!

Kailua · « **Reply #134 on:** February 24, 2014, 12:36:14 PM »

To my understanding by rsterne is that the weak point of the exposed thread under higher pressure that if the is banged or dropped under pressure if may cause a failure at that point. So if the striker adjustment was exposed outside the stock and the receiver was screwed to the stock at the inner striker block. Would the stock give the connection to receiver to air tube a solid platform being that the tube's barrel band is screwed to the stock also?

rsterne · « **Reply #135 on:** February 24, 2014, 05:18:05 PM »

The valve is so close to fitting a 7/8" OD x 0.065" wall tube you will only have to skim off a couple thou if any.... This is a good idea, but whoever told you the tube was good for 6K was dreaming.... The normal rating is 2000 psi at a 4:1 safety margin as used in the Disco....

http://www.goodyearrubberproducts.com/files/Parker/ParkerTubeCatalog4300/Parker%20Tube%20Catalog%204300examin1.Page470.pdf

Using my standard calculations, and assuming mild steel (1010) for the tubing, I get a safety margin of 2.6:1 at 3000 psi, so I certainly wouldn't use it above that.... If you step up to CrMoly tubing, then the 4:1 rating as per the chart linked above is 3000 psi, and that is what is typically used for a PCP tube on a QB78.... Since you have a bunch of the DOM, you could use it but PLEASE protect the gun with a 3K burst disc on any regulator output to make sure the pressure will never exceed that....

Bob

Kailua · « **Reply #136 on:** February 25, 2014, 12:25:48 AM »

To my understanding by rsterne is that the weak point of the exposed thread under higher pressure that if the is banged or dropped under pressure if may cause a failure at that point. So if the striker adjustment was exposed outside the stock and the receiver was screwed to the stock at the inner striker block. Would the stock give the connection to receiver to air tube a solid platform being that the tube's barrel band is screwed to the stock also?

Well anyways this is the best camera I could find. If its blurry sorry. But pics shows the XS60C with an end cap, one pic showing a sleeve to keep the screw head extended out, and one pic showing the stock screwed to the striker block. This is a home made stock but I sure the factory stock can be modified.
If anything exposing the screw might make tuning easier. JMO

rsterne · « **Reply #137 on:** February 25, 2014, 02:02:42 AM »

I'm not too concerned about the tube failing from an accident when the stock is in place.... I'm more concerned that if people overfill the gun that fatigue cracking may set in where the threads are exposed just in front of the receiver.... It the tube cracks there, it could eventually let go in a catastrophic failure.... The force pulling the tube apart there is 870 lbs. at 2000 psi, and the stored energy in the reservoir at that pressure is 5700 FPE....

I like your idea of the exposed velocity adjuster, BTW....

It should also be possible to silver solder a sleeve into the reservoir that is long enough to go about 1/4" past the threads to increase the wall thickness there.... At the front of the reservoir, a new fill fitting with the O-ring moved back behind the threads is an easy fix.... Add some high-tensile screws and you should be all set.... Then the next weak point becomes the bearing load of the valve screws in the aluminum receiver.... It just goes on and on, right, once you try and go past 1500 psi....

Bob

Kailua · « **Reply #138 on:** February 25, 2014, 02:14:44 AM »

To quote my self the rifle is what it is. As for myself if and when I get to my regulated bottled project will probably not exceed the recommended 1500 PSI. I guess I should just keep my mouth shut but figure some people are going to go over the limit no matter what and thought this might be a way something to keep things safer. thanks
Oh I forgot to add if interested the longer adjustment screw has a nut behind the spring which was locked in with a set screw.

avator · « **Reply #139 on:** February 25, 2014, 09:05:42 AM »

I need to look a little closer but, I've thought about just cutting the stock back above the power setting adjustment and adding a lever to the locking nut so that left would be loose, and right would be tight. Then just drilling a hole to insert a small screw driver to adjust the screw. I don't want to chop it up any more that ness. Mike has some stocks available, I might have to grab one. Maybe even make a wood plug for the hole.

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XS60C PCP Repeater project

Author Topic: XS60C PCP Repeater project (Read 456134 times))