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PostPosted: Mon Apr 02, 2018 10:11 am 
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Location: Coalmont BC
This reminds me of my Uber-Carbine, which was very similar, it used a 2200 tube and linkage and a 2289 valve....

Image

I still carry it in a locked box on my ATV, but I haven't used it in years, other than checking it once in a while to make sure it still works properly.... The final tune is two shots at about 590 fps on 19 pumps....

Image

It has a Disco hammer spring in it, with RVA, and if I crank it to the max, it does 605 at 10 pumps, 685 at 15 pumps, and peaks at 765 at 24 pumps....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
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Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
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Last edited by rsterne on Mon Apr 02, 2018 10:42 am, edited 1 time in total.

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PostPosted: Mon Apr 02, 2018 10:16 am 
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lol ~ it's difficult to me to count from 1 to 24 ~ [emoji16][emoji16]

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PostPosted: Tue Apr 03, 2018 3:55 am 
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Location: Winnipeg, Canada
Did a little more with the chrony tonight with fingers crossed :wink:

At 22 pumps with the same 14.3 gr Daisy h.p.:

Image

That was the highest out of a 10 shot string. Actual average is 717.5. Extreme spread is rising a shade here at 10.6 fps.

20 pumps yielded an average of 698.8 fps with an extreme spread of 10.9 fps.

Gun retains air at 25 pumps~ however, the following is presented as point of interest:

Image

That was the highest recorded tonight...

This retained air is still not making a lot of sense for me.
The gun was really barking at 25 pumps. Here are the results showing 2nd shot on retained air. I didn't want to push that old valve any harder than necessary~ so I just did a string of 5.

1.) 739.1 2nd 175.5

2.) 725.7 2nd 261.1

3.) 730.8 2nd 286.3

4.) 740.8 2nd 348.4

5.) 737.1 2nd 304.2

This is a decent start. I can do a bit more with the exhaust opening in the valve, lengthening hammer stroke, and increasing hammer spring tension with a 2200 hammer spring ahead of a yet to be made RVA.

I'm looking forward to this. Still waiting on my parts order to get here- should be soon. I'm going to apply what I've done here to the previous 2100 build in .177 and see what happens. Going to be a busy spring for me :mrgreen:

-D.S.

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PostPosted: Tue Apr 03, 2018 10:24 am 
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Gun was probably warming up during that 5-shot string at 25 pumps, hence the rising velocity on the 2nd shot.... If you set it aside to cool, the 2nd shot velocity drops.... Interesting that both our guns retained air at 25 pumps....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Tue Apr 03, 2018 11:43 am 
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Hi Bob:

Not too sure of the temperature dynamics of a valve consisting of an aluminum front, and brass rear.

That final string listed was chronied after 60 some odd shots~ I like to work my way up while I'm on a new build.
The brass piston head does get a little warm 15 pumps and above, but cools very rapidly. Personally, I can't see using a delrin head in torture test situations like these.

Kind of curious about heat retention of brass vs aluminum. My first guess is that the aluminum would cool faster with it's lighter density than brass, but could be wrong here as well.....


-D.S.

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PostPosted: Tue Apr 03, 2018 2:34 pm 
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All I know is that if I pump my Uber-Carbine 19 times and shoot 2 pellets basically right away, I get two shots at about 590 fps.... If I wait 15 minutes (inside my heated shop) the first shot is faster than the second shot, because the pressure drops as the air inside the valve cools.... If I add 2 more pumps at that point (21 total) I can take the 2 shots immediately, or wait a couple of hours, and either way both shots are again about 590 fps.... I suppose if I went outside into freezing condtions the same thing would happen all over again once the gun cooled more.... but I doubt it would be as significant.... I never tried that....

It certainly shows why in a retained-air pumper you should have some kind of pressure indicator.... even more so if you have a 3 or more shot tune.... you need to always start from the same pressure....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Tue Apr 03, 2018 5:41 pm 
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Location: Caronport, Saskatchewan
Very good point Bob, I've noticed this too, and having a pressure gauge is a great help in a multishot pumper. I'm thinking of doing just that for my next project with a lr700w pumper, with a tee adapter and16g cartridge hidden in the stock and gauge imbedded in bottom of the stock.

Looking forward to your continued experiments with springs etc Doc! Looks like you've got a great shooter there [emoji846]



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PostPosted: Wed Apr 04, 2018 5:57 am 
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Location: Winnipeg, Canada
I'm going to have to wait for my parts order to get here.

Valve stem let go tonight- she went twang splork on the 3rd warming pump. Shouldn't have pushed it like that the other night.

There's a pretty good wear ring around the top of the delrin seat-sealing surface. It sure sounded a lot like a total stem separation.
Did a few things despite the set back:

Opened the transfer port to .165", and the bbl inlet to the same diameter. Made a hurry up extended RVA out of an old worn 13-XX valve front and there's enough room in there now for a 2200 hammer spring. I think I may have a disco hammer spring laying around somewhere, if the need for it arises...

That set of numbered HSS drill bits has sure come in handy. Now I know how stock transfer ports are drilled out~ in small increments at a time :wink:

-D.S.

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PostPosted: Thu Apr 19, 2018 5:16 am 
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Location: Winnipeg, Canada
Image

Separated valve stem and pancaked poppet.

Image

Damage is obvious here from this angle. Ring around the stem base and cracks on the main body actually pass a lot of air~ the openings are very likely larger under poppet spring compression.

Image

Valve body comparison. First variant 2200 exhaust section on a 13-XX intake section at left. Stock 13-XX at centre. Current 2200 valve at right. Guess which one's the volume winner :wink:

-D.S.

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"Ain't no half-way"
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PostPosted: Thu Apr 19, 2018 10:22 am 
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Location: Coalmont BC
I have seen that type of poppet failure before, on a BAM B/51.... They use a very heavy poppet spring with very limited travel, and if you dry fire them (no air), or even fire them with low air pressure, the hammer drives the stem far enough it tries to drive it through the poppet, once the poppet spring goes coil bound....

I don't know if your poppet spring can go coil bound before the stem goes flush with the back end of the valve.... but if so, when you cranked up the hammer spring preload you could have had the same problem occur.... I always try and make sure that the stem can go just below flush in the back of the valve before the poppet spring reaches a coil bound condition.... This will prevent the hammer trying to drive the stem through the poppet....

In a valve the size of the 13XX valve, you are very unlikely to need more than 1/8" of lift, and there should be no problem arranging to have the stem protrude 3/16" from the back of the valve without having the poppet spring going coil bound.... You may be able to shorten the valve stem to achieve this.... just watch that the cocking pin on the hammer doesn't run into the end of the slot in the tube or receiver, or hit the back of the bolt on firing....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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