Author Topic: 880 replace elastomer spring (Read 5079 times))

Ronno6 · « **Reply #40 on:** July 21, 2024, 08:07:46 PM »

Quote from: Van on July 21, 2024, 07:02:54 PM

Thanks Ron, you have a nice 880 rebuild kit at a good price. Got it back together and shot over the crony. 10 pumps with Destroyers 7.4g was shooting between 630fps to 645fps I guess it will get broke in & vary a bit less. Here it is back together I'm happy with it.

Thanks for the kind words.......
I hear there is a nice trigger mod kit out there.....somewhere....

caudie · « **Reply #41 on:** July 21, 2024, 08:46:49 PM »

Pat - I like your reasoning and agree if one o-ring needs replacing the others are not far from needing replaced too. The complete "seal kit" plus an Elastomer Spring is only $1.25 and easy to replace. I am glad I replaced the Elastomer first and tested it's affect on velocity. I didn't know that it could affect performance that much. But from now on when I replace 1 piece I'll replace the others.

The next 2 in line to be tested - Checked out OK for now. I'll keep shooting them as is but will test them again after a couple 3 tins of pellets. The 4th (a refurb from Field Supply) has not been shot much at all - being stored most of the time and in pretty much new condition. It was cheap, being under $30 delivered. It's worth more to me now in parts but I'll check at least the Elastomer before using it regularly for sure. I might even get it out now that I'm thinking about it and fire a few over the chrony to see how it's doing. Been a while.

avator · « **Reply #42 on:** July 21, 2024, 09:16:00 PM »

I love the metal/metal Daisies. I have several. And yes, Ron's trigger mod is awesome.

Back_Roads · « **Reply #43 on:** July 22, 2024, 08:43:12 AM »

Yup I still have one of Ronnos trigger kits at the ready for the next 880 that comes along

Van · « **Reply #44 on:** July 23, 2024, 11:17:45 AM »

My 880 rebuild has settled in at 650-655fps at 10 pumps with Destroyers 7.4g pellets. That is what I have heard is max recommended # of pumps. I did try 12 pumps and got 680- 690fps and the extra zip was noticeable but don't know if the seals will hold up at that pressure in an 880. I pump my Crosman flat top 1377 cartridge valves to 14 pumps when shooting longer ranges. I also got better results using 30W pure silicone oil than Secret Sauce from Mac1. Anyone here had problems pumping 12 before in an 880.

caudie · « **Reply #45 on:** July 23, 2024, 11:34:14 AM »

I've pumped mine to 12 pumps a few times but usually shoot it with 4-6 pumps. Pblawler has quite a few metal/metal older guns that he mod's. As a kid he said him and his friends used to pump them up to 20 pumps regularly. He recommends replacing the abutment pin with a harded steel pin or a cut off 1/8" drill bit for 20 pumps now. He also has a pbl power mod which he swaps out the Elastomer and pump head from a Daisy/Win 1977xs and uses 20 pumps in them regularly.

caudie · « **Reply #46 on:** August 06, 2024, 01:58:49 PM »

Since the last chrono test about a year or so ago the second Daisy 880 I tested lost 5 fps at 10 pumps with 9.8 gr Black&Gold WRN. At 6 pumps with 7.7 gr Black&White WRN it gained 11 fps. The third 880 lost 10 fps at 10 pumps with the 9.8 gr WRN and the fourth 880 lost 7 fps with 10 pumps with the 9.8 gr pellets. I'll continue shooting these and test them again in a few months or so. These lost a little but not enough to have to refresh them yet.

Ronno6 · « **Reply #47 on:** August 06, 2024, 03:26:22 PM »

These bumpers (easier to type than "elastomer spring") do take a set after bring compressed for some time.
This results in them giving ground at a lower pressure than when new, giving lower pumping efficiency.
Closing the pump handle to the latched position and storing the rifle that way makes the problem even worse,
as the bumper is further compressed, even if just a little.
A coil spring ala that in the Winnie 1977 would have been a better choice....

caudie · « **Reply #48 on:** August 07, 2024, 07:08:29 PM »

Well, I'm still thinking about these Elastomer Springs. I needed a small project today to keep me busy, so I thought I'd take the #3 Daisy 880 that lost the most in velocity and change out the Bumper. When I got it out I measured the Bumper (.420 in length). Not really having a quess at the length seeing it was only 10 fps down from normal. So another thought comes to mind - what would a shim do to restore it to normal. I took a #10 washer (od .5 & id .219), drilled the ID out to .25 to shim up the Bumper. The only thing that could screw up shimming the Bumper if when compressed it may be too large to go into the compression chamber. Measuring the OD of the Bumper (.720 when compressed)) it should have enough clearance to work fine (piston .730 + o-ring at .76). When installed the velocity returned to normal - gaining back the 10 fps + a little. Question 1) was it worth the effort? 2) How long will it work - It really would have been easier to just replace the Bumper with a new one. Sometimes I just need a question answered - so it was worth the little extra time to try it for me.

Since the New Bumpers I have range from .485 to .494 it gives a little bit more use but how much? If only a week or month - Not much. But if it lasts 8 to 12 months or more, maybe it'd be worth while. I don't see this as a permanent fix but a new bumper isn't either.

Now I have a question for Ronno6 - have you done any research on a steel spring to replace the bumper? I know I can use the Spring from a Winchester 1977 but at $15 + shipping replacing 4 in these guns would add up rather quickly. There's lots of springs that could be made to fit but
the wire size would be the problem What size wire would approzimate the pressure required to work like a bumper? I may just have to make a trip to a local store and see what I can come up with.

Another question came to mind. Buying a complete piston assembly to replace a Bumper has come up. While I agree that it would be an easy way to replace a Bumper - I think the best solution to this would be to only buy the assembly when needed. If an assembly was stored any length of time the Bumper on it would take a set if only a little. I don't know if it will help but I've disassembled the piston assembly I have on hand to keep it in the best possible condition if/when I need it. Right now I think changing to a New Bumper is probably the best bet for the longest service.

Probably should have just changed it out - but I just wanted to see what it would do. I didn't loose anything but a few minutes time so I guess I'll find out.

Ronno6 · « **Reply #49 on:** August 07, 2024, 08:39:06 PM »

I sent inquiries to a few spring manufacturers but never received a reply or offer.
Uncertainty as to the material and spring forces could contribute to the lack of response.
I was in purchasing for over 25 years and purchased many made-to-print coils, but
have been out of the game for over 20 years now and all my passed contacts have retired also......

It is a bummer that Daisy does not sell this spring on its own, but that is a testament to its longevity.
That, plus IIRC there are some dimensional differences in the envelope size that would require changes to other parts in the assy.
Use of the 1977 piston assembly requires alterations...the pivot pin hole requires relocation the the end of the link ahead of the pivot pin needs to be shortened about .060" or so... If done correctly, no alteration to the pump tube intake slot is necessary.

There have been members who have replaced the ES with a solid stack of washers and realized performance gains.
That would be an easily machinable single component, but removing the desirable compressibility of the ES and the
desired give in the system if the cam-over state is reached means (to me) that the stress is transferred to other components in the system........ the next weakest link theory may come into play...

Back_Roads · « **Reply #50 on:** August 08, 2024, 12:06:32 AM »

A stack of beveled washers like in a regulator, or a stack of split lock washers spaced with washers sized to fit

caudie · « **Reply #51 on:** August 08, 2024, 01:44:47 AM »

James quote: "A stack of beveled washers like in a regulator, or a stack of split lock washers spaced with washers sized to fit."

I don't know anything about the beveled washers in a regulator but the stack of lock washers spaced with washers seems to me would work for a Elastomer Spring. The load is there for just a very short time and that might be just the thing for the Bumper effect. Thanks James, that'll be something I could get and try out.

avator · « **Reply #52 on:** August 08, 2024, 07:44:15 AM »

I wonder if a section of gas line hose or the like with a washer on both ends would work.

Ronno6 · « **Reply #53 on:** August 08, 2024, 07:52:41 AM »

Quote from: Back_Roads on August 08, 2024, 12:06:32 AM

A stack of beveled washers like in a regulator, or a stack of split lock washers spaced with washers sized to fit

Um Belleville wshers?
https://en.wikipedia.org/wiki/Belleville_washer
Worthy of consideration!
But...NOT inexpensive...typically about a buck apiece.
Work loads all over the place, that spec is cumulative and calculable when stacked.
Still, could work.... maybe use a few bellevilles for load, sandwiched between flat washers to achieve stack height and save $$$
The unknown is the load specs for that dastardly elastomer spring.....I doubt even Daisy knows...
Anybody have a load tester??

Back_Roads · « **Reply #54 on:** August 08, 2024, 08:14:35 AM »

Quote from: avator on August 08, 2024, 07:44:15 AM

I wonder if a section of gas line hose or the like with a washer on both ends would work.

The rubber is a very solid rubber hard to compress in a vice even Bill, why we are looking for better options with strong resistance. If it did not take a set and could compress 1500 psi perhaps

Ronno6 · « **Reply #55 on:** August 08, 2024, 02:19:31 PM »

I am looking at Belleville spring washes as a non-tiring replacement.
But i could really use some spring rates for the Daisy part.

I have contacted Daisy in an effort to find out, but received no response as yet.

I am wondering if using a digital torque wrench a value can be obtained by compressing the ES to the proper length using a 1/4" bolt setup?
Determine how much torque is required to compress to length, then try different combinations of Belleville washers to achieve a similar value.........hmmmmmmmm

caudie · « **Reply #56 on:** August 08, 2024, 03:39:54 PM »

Ron - This might be relevant.

http://forums.y-blocksforever.com/Topic60563.aspx

Ronno6 · « **Reply #57 on:** August 08, 2024, 03:59:42 PM »

Quote from: caudie on August 08, 2024, 03:39:54 PM

Ron - This might be relevant.

http://forums.y-blocksforever.com/Topic60563.aspx

Would probably work, but I don't have one..........
An absolute value would not be as important as a relative value between systems...

Ronno6 · « **Reply #58 on:** August 11, 2024, 02:04:11 PM »

What is needed is to establish how much compression is needed when the pump assy. achieves the cam-over state.
Belleville washers in the appropriate size do nor deflect much, in the range of .004 - .010"
Stacking face to face would increase the deflection, but reduce the rate.
They would need to be used in conjunction with a solid spacer.
If the washer system is totally compressed at cam-over, rate would not be
important, as the system would become inflexible with the solid spacer used.

My brain is hurting.........

caudie · « **Reply #59 on:** August 11, 2024, 02:31:55 PM »

I hear that Ron. I went back in to the shimmed ES - removed it and replaced it with a new one. It had a little harder cam over so didn't want to create a new problem. I'm OK with the bumpers - easy to replace and work well for quite a while. I do wish that Daisy would start selling the Spring in the 1977 assembly individually though - probably not going to happen.