GTA
Airguns by Make and Model => Vintage Air Gun Gate => Topic started by: Rob112o on January 23, 2017, 05:28:11 PM
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Working on these vintage pumpers be it a Sheridan, Benjamin, and sometimes Crosman I come upon different/odd parts. Last couple rebuilds I've come across 2 things out of the norm, both from Sheridans. The first was from a 1968 Blue and it was the 2 piece bolt. Where the loading pin was a removable piece, not meant to be, but still does come loose on accident. Usually lost down range as it was shot out. I was able to get a loading pin off the yellow. I didn't think it was gonna happen.
This time around it was on a 1979 Silver Streak. The only reason I came across it was because I plan on selling. It worked just had some quirks. She's always held air anytime I check on her. In very good overall condition and shoots accurately, not that that's a surprise. Couple of the quirks, it would leak for a second or 2 and stop. I just thought I couldn't hear it leaking anymore. I'd come back and discharge several weeks later and would still have the air. I've done a 10 shot 8 pump string a while back and it's clear this slight leak was causing the deviation to be so large. Also causing a low FPS. http://www.gatewaytoairguns.org/GTA/index.php?topic=112378.msg1102961#msg1102961 (http://www.gatewaytoairguns.org/GTA/index.php?topic=112378.msg1102961#msg1102961) The other quirk being something rattled in the valve. I figured it was the check valve spring. Now, I'm not gonna tell you what it is just yet. Let's see what y'all have come across.
Pic of rifle:
(http://i1030.photobucket.com/albums/y364/Rob112o/Mobile%20Uploads/2016-09/D7698406-500F-438C-8AA3-461D56537B39_zpstoi0ghvf.jpg~original) (http://s1030.photobucket.com/user/Rob112o/media/Mobile%20Uploads/2016-09/D7698406-500F-438C-8AA3-461D56537B39_zpstoi0ghvf.jpg.html)
Pic of the parts. She was very clean and by the look of the trigger blade very little use in her 38 years of life. (Pic isn't here yet I'm uploading on Stupidbucket)
(http://i1030.photobucket.com/albums/y364/Rob112o/image_zps4bxjmccd.jpeg) (http://s1030.photobucket.com/user/Rob112o/media/image_zps4bxjmccd.jpeg.html)
(http://i1030.photobucket.com/albums/y364/Rob112o/image_zpsnki08ozt.jpeg) (http://s1030.photobucket.com/user/Rob112o/media/image_zpsnki08ozt.jpeg.html)
(http://i1030.photobucket.com/albums/y364/Rob112o/image_zps1zbbha5f.jpeg) (http://s1030.photobucket.com/user/Rob112o/media/image_zps1zbbha5f.jpeg.html)
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what's the little black thing, centered between the hammer and valve spring??? obviously, that's what was rattling in the valve. looks like a tiny grub screw.
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That little black thing goes in the spring behind the trigger, there is a little indent hole it must help retain the trigger spring in alignment . best i can tell w/o a close up of that little thing ?
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Bingo, it is that little black thing. A close up you ask?
(http://i1030.photobucket.com/albums/y364/Rob112o/image_zpsusaygqas.jpeg) (http://s1030.photobucket.com/user/Rob112o/media/image_zpsusaygqas.jpeg.html)
This would be a first Dan form the 70's onward that had 2 lead seals on the valve. Also the only on that came out with the valve body when I removed it. As you know how difficult that forward lead seal can be to get out.
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Is that a tiny cap nut? Goes on the threaded end of the valve stem?
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Kind of what it looks like, and explain why it was found where it was.
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That little black thing goes in the spring behind the trigger, there is a little indent hole it must help retain the trigger spring in alignment . best i can tell w/o a close up of that little thing ?
Actually the purpose of the little thing you are talking about is a trigger stop. I suppose it could also act as a spring guide. I take them out of my Dans. I like the trigger to follow through after the shot. I would tend to agree that it goes on the valve stem. Especially because the valve stem is threaded.
Something else I noticed in the OP's pic. Is it common to have 2 washers in the valve between the springs?
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Is that a tiny cap nut? Goes on the threaded end of the valve stem?
Good eye Terry! It threads onto the bottom of the valve stem. It's a little brass cap it was fresh out of the valve when I took the pic so little dirty. As you can see by the pic below a little bit of volume will be added to the valve with the base being smaller.
(http://i1030.photobucket.com/albums/y364/Rob112o/image_zpsgvsmqnxj.jpeg) (http://s1030.photobucket.com/user/Rob112o/media/image_zpsgvsmqnxj.jpeg.html)
So the weirdest thing was, the stem actually unthreaded right through the base. It's a 4 piece valve stem; the cap, base, the rubber washer inside base, and stem w/ threaded end. I've come across valve stems that unscrewed off the base, like in bottom image. (You can see the the "cap" wasn't removable on this one). But, never one that goes through the base. Just when I thought I had Sheridans figured out. They go and throw me a screwball.
(http://i1030.photobucket.com/albums/y364/Rob112o/image_zpsk5gr1tao.jpeg) (http://s1030.photobucket.com/user/Rob112o/media/image_zpsk5gr1tao.jpeg.html)
The benefit would be a much easier valve stem for replacing the rubber washer. On the above valve stem I was able to get out the rubber washer easier and replace and screw stem back on.
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That little black thing goes in the spring behind the trigger, there is a little indent hole it must help retain the trigger spring in alignment . best i can tell w/o a close up of that little thing ?
Actually the purpose of the little thing you are talking about is a trigger stop. I suppose it could also act as a spring guide. I take them out of my Dans. I like the trigger to follow through after the shot. I would tend to agree that it goes on the valve stem. Especially because the valve stem is threaded.
Something else I noticed in the OP's pic. Is it common to have 2 washers in the valve between the springs?
If you look closely you can see I already replaced factory trigger spring and removed the little pin which acts like a trigger stop. It's sooo much lighter now. About the 2 washers, I usually come across that in Benjis this was a first on a Dan.
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I would be surprised if that gun, with the two washers in the valve, didn't hold some air in the valve with 8 pumps. Maybe even less.
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if you take a closer look, that valve stem and spring belong in a Benjamin, not a Sheridan. the Sheridan stems had a much larger spring seat, to center the larger diameter spring. the 4 piece valve stem was a common one, found in the 310, 312's. wonder how it ended up in a 70's dan?
as far as the extra washer, I've seen a couple sheridans with two washers in them. never could figure out why, though.
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It wasn't ever dumping 8 and wouldn't always dump 5 or 6 either. I think that little cap was getting in between a coil ever now and then. It was never consistent on a follow up shot to clear valve. Sometimes it would sound like a fart of air other times at least a pump and occasionally enough that it would have sent a pellet if loaded.
Scott, I concur with that. Some of the internals didn't look to be from this rifle. Especially, how clean it all looked. Other than that cap everything else was almost free of blackish oil. So I'm guessing someone attempted a rebuild. Well, the original owner or whoever he had do it. This rifle was bought brand new by the person I bought from.
It's dumping now a full 8 pumps. I swapped out the spring inside with a stout spring, but 2 coils shorter. It needs to be cocked to pump. Which isn't an issue since the Dans can be un-cocked. I just need to get her on the chrony now.
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When I tore my dan down it had the 2 washers , so they went back in ,since it was used to them there ? I thought it odd and maybe some one wasn't a good counter in the assembly line ?
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Hmmm, bit of a stumper going on with this Dan. She does a full clear on 8 FPS. It has to be cocked to accept the first pump. Once cocked you can slow pump it, fast pump it, doesn't matter the air goes in with no escape out the barrel or breech. 10 shots 8 pumps after just being resealed:
1. 444
2. 463
3. 506
4. 519
5. 517
Oil
6. 534
7. 541
8. 543
9. 545
10. 546
Day 2
1. 555
2. 554
Remove felt bumper
3. 561
4. 558
5. 572 with 9 pumps, full dump.
That's when I gave up. I'm sure I can pump up to 11 and get 610-620, but that's clearly not right. I thought my chrony may be out of wack. So I took out my 65 Dan and got 645 which puts her close to her average. There is a difference about the 78. When the arm is fully opened the actual pump cup clears the slot in the tube. I just looked at all my other Dans and none do this. A couple have some of the cup visible, but none like this:
(http://i1030.photobucket.com/albums/y364/Rob112o/image_zpsayucvv9t.jpeg) (http://s1030.photobucket.com/user/Rob112o/media/image_zpsayucvv9t.jpeg.html)
Y'all think that could be causing the issue? Some of the immediate air is lost right there when I start my stroke? I should have taped the "Air Hole" and tried pumping. I'll do that tomorrow.
Here is a link to her numbers prior to the rebuild. With all those original parts I had found in her, minus the pump cup.
http://www.gatewaytoairguns.org/GTA/index.php?topic=112378.msg1102961#msg1102961 (http://www.gatewaytoairguns.org/GTA/index.php?topic=112378.msg1102961#msg1102961)
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piston rod's too short. I have the same thing with my '67. only cure is an adjustable rod.
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An adjustable piston from Mac1 is a good investment. I put one in my '67 Streak.
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Just another idea..
Check how loosely the valve pin fits in the valve. If it's too loose air will escape out the back of the valve instead of passing thru the transfer. In your case, it does look like the piston rod is too short. We already know someone put different parts in the gun.
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Today I put my face near the "air hole" and I could feel air as the cup starts compressing. If I'm opening the pump arm and cover the "air hole" it will still gasp air since the pump cup passes the tube slot. So I did some measuring of things today. I sized up the 79's piston with a 68's. The 79's piston measures in at 7 9/32. The 68's measures in at 7 5/16. So quite a small difference:
68 left and 79 right
(http://i1030.photobucket.com/albums/y364/Rob112o/image_zpsbq60woyy.jpeg) (http://s1030.photobucket.com/user/Rob112o/media/image_zpsbq60woyy.jpeg.html)
The noticeable difference was in the slot in the tube. The 79's slot measures 8 3/8. The 68's slot measures 8 5/32:
68 Blue 79 Silver
(http://i1030.photobucket.com/albums/y364/Rob112o/image_zpscvbgikug.jpeg) (http://s1030.photobucket.com/user/Rob112o/media/image_zpscvbgikug.jpeg.html)
I checked the other 79 Silver Streak I have and it also has the slot length being 8 3/8. I decided to swap the 68 and 79's pistons. Which solved the problem of the cup passing the slots. Doing this got me an increase in FPS. She is now averaging 584 from 545 FPS. Still I feel she should be higher. She dumps all air at 9 shooting 590 FPS. The other 79 Silver is doing 638??
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Looks like you have a version of a " FRANKENDAN " rather than a Sheridan. LOL
Yes, FPS should be higher than that , so something is still wrong.
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You could be getting some blow by, during the shot. Pop the back off, and retighten the valve nut.