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PostPosted: Sun Oct 17, 2021 7:55 pm 
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I was searching for O-rings for the x53 Daisy when I came across a 3 part Blog on Pyramid, and happened upon this concerning power mods:
There is also the little nub on the pump arm latching detent that protrudes into the hammer channel and serves to cushion the hammer strike against the valve since the hammer hits it and causes the spring for the pump arm detent to absorb some of the hammer strike that would other wise fully open the valve. I cut that nub off of my pump arm detent so the hammer can open the valve fully when it is released upon firing. So its those two mods that I did that got mine up to the stated spec that daisy says it should shoot.

It is in the comments below the article by BB P: https://www.pyramydair.com/blog/2016/05 ... 53-part-3/

Anyhow, my Q is where is this nub he speaks of? any details on its removal? My 853 has the pump cup filled, no other power mods and I'd really like to add 20 fps to get it to 495. Here is a couple pic of the pump arm and the latch:


Attachments:
Nub.JPG
Nub.JPG [ 85.57 KiB | Viewed 917 times ]
daisy pump.jPG
daisy pump.jPG [ 59.94 KiB | Viewed 917 times ]

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PostPosted: Mon Oct 18, 2021 5:14 pm 
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Duke I believe Bulldawg spoke about the spring-loaded sliding part into the receiver, the part that actually locks the pump arm in the closed position. I didn't take my 953 apart to check but I strongly suspect this is what he meant. May have a go at it next week-end.


Attachments:
953_latch.JPG
953_latch.JPG [ 31.94 KiB | Viewed 866 times ]

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PostPosted: Mon Oct 18, 2021 5:29 pm 
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OK, seen. That makes more sense. I don't have my 853 with me and i can't understand how the hammer would interact with this "latch", so if you do figure it out I'd be grateful for some tips and pics.

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PostPosted: Sat Oct 23, 2021 8:46 am 
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Update:

I've taken my 953 apart, and found some interesting things. I'll pass on the dis-assembly of the rifle, and go straight to the point.

There's indeed an interaction between the hammer and lever latch. The little nub on the pump arm latching detent that protrudes into the hammer channel is there, and looks to effectively cushion the hammer end-stroke by about 1/16''. The latch spring is quite heavy, and has a preload when installed, so I have no doubts it may have an effect, albeit small.

First picture shows the lever latch, second pic shows the parts installed in their correct positions.

As a small note, I can add that there's not much hammer impact marks on the front hammer channel wall, just some ''wear'' marks, so I guess it's another clue the small nub does its job. That brings me to think that maybe it's there to avoid cracking the potmetal part of the channel, after many impacts on the front wall. The small nub is maybe just a durability feature, and not specifically a power-limiting device?

Will update again as soon as I can.


Attachments:
x53_latch_1.JPG
x53_latch_1.JPG [ 79.84 KiB | Viewed 794 times ]
x53_latch_2.JPG
x53_latch_2.JPG [ 59.24 KiB | Viewed 794 times ]

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PostPosted: Sat Oct 23, 2021 10:47 am 
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Note that as with any pneumatic that uses a hammer, allowing the hammer to travel further may not open the valve further.... How far the valve opens usually depends on the pressure inside the valve.... Since the 853/953 dumps all the air in the valve on firing, then by definition the valve is opening far enough to do that.... If removing the bump stop for the hammer does any good, it could only be because it is allowing the valve to open a bit faster, not because it is increasing the lift or dwell (how far or long it is open).... Once the valve opens to 1/4 of the throat diameter, it cannot flow any more air....

This is very much a "if it works, then it works" kind of mod.... The downside is removing the latching mechanism for the pump handle will likely cause the pump to fall open when the gun is not cocked (pressurized), which could be annoying.... In addition, if that stop prevents the hammer from hitting the pop-metal valve casting, it could of course eventually crack.... Allowing the hammer to bounce off the back of the valve in some guns actually reduces the velocity because that rebound shortens the dwell, although that is unlikely with an SSP.... There is also the concern of having the gun exceed 500 fps if you don't have your PAL, of course....

Bob

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PostPosted: Sat Oct 23, 2021 10:59 am 
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Awesome. Good point about the cushioning. I have to believe Daisy put that nub there for good reason. The post I refereed to is the only one mention of this mod I ever saw, so if you are going to check if it makes a power increase, maybe reassemble without the latch and run a few over the chrony before making any un reversible changes. If there is a power increase, maybe a very thin rubber washer/gasket could be put in there around the valve stem to cushion the impact if it does happen with the nub removed. All this for 20 fps... maybe not worth it, eh?
And Bob, the reason for doing this would be to bring the speed up to close to 495. Many of these Daisies are relatively weak out of the box. Mine is struggling to reach 470 fps with RWS Hobbies. I believe the 'merican 853 could shoot 520 ish.

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PostPosted: Sat Oct 23, 2021 11:13 am 
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It looks like Airmec only removed the latch spring, which allowed the black rubber part to slide further forward, out of the way of the hammer.... That should tell you if the mod works, without cutting off the nub....

Bob

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PostPosted: Sun Oct 24, 2021 5:27 pm 
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rsterne wrote:
It looks like Airmec only removed the latch spring, which allowed the black rubber part to slide further forward, out of the way of the hammer.... That should tell you if the mod works, without cutting off the nub....

Bob


Yes I removed the spring for demonstration purpose, but when the pump arm is closed the latch is further rearward, giving the 1/16'' ''cushion''. The latch is actually made from a hard plastic, easy to work with a rasp and sandpaper.

Dukemeister wrote:
Awesome. Good point about the cushioning. I have to believe Daisy put that nub there for good reason. The post I refereed to is the only one mention of this mod I ever saw, so if you are going to check if it makes a power increase, maybe reassemble without the latch and run a few over the chrony before making any un reversible changes. If there is a power increase, maybe a very thin rubber washer/gasket could be put in there around the valve stem to cushion the impact if it does happen with the nub removed. All this for 20 fps... maybe not worth it, eh?
And Bob, the reason for doing this would be to bring the speed up to close to 495. Many of these Daisies are relatively weak out of the box. Mine is struggling to reach 470 fps with RWS Hobbies. I believe the 'merican 853 could shoot 520 ish.


I went further and made a new hammer with a front ''bumper'' made from UHMW polyethylene. The new hammer weighs exactly the same as the original, so that shouldn't have influence on the test. I also modified the latch by filing the nub down, but left a small portion for it to stop where it's supposed to when the pump arm is open.

Sorry I haven't had the time to put the rifle back together and test it, I'll be updating soon.


Attachments:
953_hammer_7.JPG
953_hammer_7.JPG [ 53.65 KiB | Viewed 741 times ]
Modded_latch_1.JPG
Modded_latch_1.JPG [ 35.75 KiB | Viewed 741 times ]
Modded_latch_2.JPG
Modded_latch_2.JPG [ 47.07 KiB | Viewed 741 times ]

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PostPosted: Sun Oct 24, 2021 7:16 pm 
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Well I saw I made a design error :oops: . The valve stem is not centered in the hammer channel, and the center button on my hammer would not touch it by much, being too small (1/8''). I drilled the small button out and pressed a bigger one (5/16'') in place, problem solved, and still plenty of bumper surface 8) .

Edit: Just a small detail: the button is recessed 0.010'' from the bumper surface, so it shouldn't contact the front wall.


Attachments:
953_hammer_V2_1.JPG
953_hammer_V2_1.JPG [ 34.26 KiB | Viewed 729 times ]
953_hammer_V2_2.JPG
953_hammer_V2_2.JPG [ 48.2 KiB | Viewed 729 times ]

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PostPosted: Mon Nov 01, 2021 1:59 pm 
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Update:

Had to rework the hammer again, as the front ''bearing'' part was too long. A new hammer MUST have the same exact dimensions as the original. I also made a new, heavier spring guide to compensate for the loss of steel, and hardened the rear lip where the sear catches.

Again I'll pass on a few details and get to the results: I observed a gain of about 17 fps directly related to the latch mod.

My Daisy 953 has the piston filled, the bolt probe now has an Oring, and it has the latch mod. These are the only power mods. Before the mods it was shooting a RWS Hobby 7 grains pellet @ 402 fps, now in a 5-shots string I observed a maximum velocity of 491 fps with these same pellets :shock: . I can't say I'm not happy with these results!


Attachments:
953_hammer_V3_1.JPG
953_hammer_V3_1.JPG [ 92.67 KiB | Viewed 659 times ]
953_w_Hobbys7gr.JPG
953_w_Hobbys7gr.JPG [ 35.27 KiB | Viewed 659 times ]

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PostPosted: Mon Nov 01, 2021 2:34 pm 
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Awesome. Thanks for the detailed work and careful and thorough documentation.
I will be attempting the latch nub removal when I get the chance and will report back on the before/after results. Mine has pump cup filled, and no other power mods - going from memory it was doing about 470 with Hobbys - so the nub mod would give it 490 which is where I want it to be.

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PostPosted: Mon Nov 01, 2021 4:54 pm 
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You're most welcome Duke :drinkers: . That was a fun journey :)

Just want to add some small tech details: the 5 shots I checked were all from 487 to 491 fps, so spread is pretty good despite the mod, maybe even better than before. Due to a faster poppet opening as Bob suggested? No parasitic variations due to the heavy latch detent spring? Dunno, but a shot from my 953 now reminds me of the straight shot from an oldie Crosman self-cocker!

Also, though this wasn't an issue, there's no more hammer bounce (there was some before), and hammer/shot cycle is much smoother. UHMW polymer seems to be good for absorbing the hammer impacts, maybe an alternative for the BStaley mod? I may well re-try it in future projects 8) .

Cheers!

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