Author Topic: XS60C PCP Repeater project (Read 456249 times))

Sfttailrdr46 · « **Reply #1340 on:** January 07, 2016, 07:06:31 PM »

ROFLMBO you guys crack me up this is better than any therapist any day, this place and a nice glass of Glenn Fidich and I'm good

stalwart · « **Reply #1341 on:** January 09, 2016, 04:47:06 AM »

Also, demonstrably, cost effective. I mimic that, with a different liquid.

On that theme, as we wait for favorable conditions, I present the cam even I can afford to ruin. Sold on ebay, the clip didn't even have a spring (they didn't mention that)... $5. I just hated the idea of ruining the "fine" camera I combine with my even worse photographic skills to bring you all into the shop.

The base is very magnetic, I'll be using a can of paint to get the height (won't have to wipe down a tripod). Salvage...

If you don't count the ruined fittings, the entire rig came in under $100, parts and materials. There's no excuse for not knowing what we are going to learn.

stalwart · « **Reply #1342 on:** January 10, 2016, 07:05:18 PM »

Well, guys... here's something. I got sick of waiting on the weather to dry up, and did this inside. Mistake. I have a real mess to clean up.

This vid isn't worth editing (I pre-focused the cam, then moved it a couple feet back without remembering to refocus it), so I just posted it up here:

As you can see, the new fitting started to leak before any other failures. You can see the gauge dropping before each new stroke (at about 3K), then the puddle forming as the leak develops. The screws failed at 6K, after seriously stretching the holes in the receiver.... and, for some reason that ruined the gauge... somehow leaving it permanently stuck at a pressure it never saw. Any ideas why?

rsterne · « **Reply #1343 on:** January 10, 2016, 09:46:25 PM »

So the gauge was mounted to a piece of steel that simulates the valve, fastened in with the two stock screws and sealed with an O-ring just ahead of the screws?.... What was the test subject gun?.... thread tolerances?....

Bob

stalwart · « **Reply #1344 on:** January 10, 2016, 10:01:59 PM »

Correct. The screws failed as the designer intended. If it was a valve/block in there, it would have vented out the bottom of the receiver and into the stock cavity (in an intact gun), leaving the shooter intact, and wondering what the h*** just happened.

The gun is DT1... .017" thread engagement. Again the unknown designer I have come to respect (very much) knew what he was doing by putting in an "absurd" amount of overlap between the tube and receiver.

I have been DQing set ups with equal or slightly more engagement... I don't regret that a bit, and this just makes me feel even better about that standard.

rsterne · « **Reply #1345 on:** January 10, 2016, 11:30:32 PM »

That 0.017" is per side?.... so a diameter difference of 0.034" between the tube OD and the receiver ID?.... pretty much in the middle of the tolerance range, IIRC....

Bob

stalwart · « **Reply #1346 on:** January 10, 2016, 11:42:24 PM »

Correct. I'm thrilled with the result... quite reassured.

I just noticed something in the vid: You can see the blue fluid, I added directly to the tube, leaking out the fitting, yet much of the stuff seen in frame after the failure is the brown stuff from the pump. I was a bit shocked at the force generated... as the mess seen, in frame, prior to the test was made carefully bleeding the air (as you suggested).

The action and the probe each moved quite a ways (over 2')... and I couldn't figure out how enough air remained to do that. The shock even very slightly moved the cam (at least the lens, 40" away).

I now believe I have demonstrated how much force can be retained (and quickly returned) by the hose. The splatter pattern is pretty clear...

rsterne · « **Reply #1347 on:** January 11, 2016, 01:46:28 AM »

Maybe you had some air in the pump?.... you sure had some, somewhere.... or as you say the hose was expanding.... Lots of stored energy there, so be careful....

Bob

stalwart · « **Reply #1348 on:** January 11, 2016, 02:16:23 AM »

I back fed some blue, tube raised, then closed the valve and pumped it back through... topped it off, sealed it, and bled through the Fosters. The gauge came off zero within a fraction of a pump. You can't see it (thanks, Eric

) but the test started with just a few pounds in it.

That's why the leak showed blue. I think it would have turned brown, soon, if I had just stayed under 6K. The blue mess the gun left was pure... and the oil stayed in until it stopped (separate mess). I grabbed a screen shot of the vapor trail as it left the frame... somewhere in the 46th second. I'll see if it can be seen within the 200KB limits.

I'm convinced it was the hose... and, I don't want to get any closer to the guns. Got some thinking to do. About containment.

rsterne · « **Reply #1349 on:** January 11, 2016, 02:41:32 AM »

Actually, those screws did pretty good to stand 6000 psi.... The end load is 2615 lbs.... The root diameter of 5mm x 0.8mm screws is 0.152-0.162", so that works out to an area of 0.0181-0.0206 sq.in. each... and a stress at failure of 63Ksi - 72Ksi.... which if the 60% of tensile at shear is correct, means they had a Tensile strength of 106Ksi - 120Ksi.... That places them at about a Grade 5 or just under.... It also means that with a 3:1 safety margin, the gun should never see more than 2000 psi.... so right there, you have your first important piece of information.... BTW, the information I have on safety margins for pressure vessels is a minimum of 3.5:1 using UTS (ie to burst).... Using that, with a 6000 psi failure, we get MSWP of 1700 psi.... with the test data to back it up.... Incidently, when I first did my safety assessment of the FD-PCP I warned that the screws were the weak point (after the pockets stretched first), but all of that was based on mild steel because I was not privy to what the materials are....

Bob

StevenG · « **Reply #1350 on:** January 11, 2016, 01:45:53 PM »

Quote from: stalwart on January 10, 2016, 10:01:59 PM

Correct. The screws failed as the designer intended. If it was a valve/block in there, it would have vented out the bottom of the receiver and into the stock cavity (in an intact gun), leaving the shooter intact, and wondering what the h*** just happened.

I am pretty sure a change of pants would have been required as well.

avator · « **Reply #1351 on:** January 11, 2016, 03:31:47 PM »

You guys sure know how to have fun !!!

stalwart · « **Reply #1352 on:** January 11, 2016, 03:38:57 PM »

Bob, I'm impressed with all I've seen here. To take a random sample, and see it perform EXACTLY to spec, says a lot about the gun.

I'm tickled I could put together something good enough (but, only once) to do it's end.

I'm still mystified by the gauge damage. It didn't strike anything... trying to figure out what might have caused a pulse in the last micro-seconds. I cannot afford to buy a gauge for every test.

Steven, I'm not going to pretend, even for a second, that your statement wouldn't apply to me.

Bill, is that an offer to help clean up? That will be "fun"! I just walked away... with all the broken stuff in hand... lol.

stalwart · « **Reply #1353 on:** January 11, 2016, 07:21:37 PM »

Guys, next time you see Santa, be sure to thank him. There is abundant proof we destroyed a perfectly good gun.

Edit: never mind... it's not downloading properly.

stalwart · « **Reply #1354 on:** January 12, 2016, 11:23:17 AM »

I was asked a question I should have anticipated, and answered in the first post about this:

There is no measurable change in any of the other parts.... not a single thousandth. Nothing puffed up enough to stretch.

I remain impressed.

rsterne · « **Reply #1355 on:** January 12, 2016, 01:52:14 PM »

Yes, it would appear, based on a random sample of one, that a 2000 psi fill pressure is not completely unreasonable, but certainly not above that, to maintain a 3:1 safety margin to the failure point of the weakest link, the screws.... I assume you were using the stock front fill fitting and CO2 retaining collar/nut?.... and that the threads there had the same 0.017" overlap?.... Any sign of angling or other strain on the retaining flange on the CO2 nut?....

It will be interesting to see what happens when you test guns with less thread overlap and the threads cut deeper into the tubing wall....

Bob

StevenG · « **Reply #1356 on:** January 12, 2016, 01:57:59 PM »

Have you yet found the worst possible combo, oversize receiver and undersize tube?

A random sample of one is nice, but let's see what happens when you lose the pcp lottery, so to speak.

stalwart · « **Reply #1357 on:** January 12, 2016, 02:26:16 PM »

The nut had only .001" less engagement, and showed no damage.

I have a wide range of sizes to try, as soon as I figure out why the gauge failed... and find a good substitute fluid. I'm not interested in spraying $9 worth of fluid everywhere, and buying a new gauge for each test. I will tap the fitting deeper to see if I can save it... and will look into cutting additives to see what can be done to water to allow it to be left in the pump between tests. Could use some help with that.

As to worst case... DT2 is, as it was delivered, as close as we need to go, I'm betting. I'll set up even worse, if it's fate leaves any doubts.

avator · « **Reply #1358 on:** January 12, 2016, 04:43:52 PM »

Guys, am I correct in assuming that ya'll are testing the Gen I FD-PCP? If this is the case, is it possible to dedicate a thread? I suppose I could read through 68 pages of information to be certain.. if I weren't so old and lazy. And... Bob, did you just say that (if my random FD-PCP has the same or better match up on the threads as the one Eric tested) that filling to 2k would fall within safety margins? As stated before, I've degassed all three of mine and found no substantial loose or wiggle but, it would be nice to be able to enjoy these gun in the same comfortable fashion as I did before the "disaster". I did not specifically mic ID or OD but, I have been reluctant to put more than 1200 psi in any one of them since the formal GTA warning. With a 36" fill hose, I'm wasting a lot of air per fill with my 3300 psi 100 cf tank.

avator · « **Reply #1359 on:** January 12, 2016, 04:45:27 PM »

BTW... I do realize that this testing is very preliminary.

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XS60C PCP Repeater project

Author Topic: XS60C PCP Repeater project (Read 456249 times))