Slide diaphragm replacement, oh what fun!

[Greg B]

Started thinking about replacing the diaphragms on my slides. A couple were damaged. Just the diaphragm, not the entire assembly. Got 4 new ones from a guy in Australia.
I also was curious about the weight of the assemblies.
I had a brand new slide and it weighed in at 57.34gr.
the old ones were:
57.18
57.01
57.18
57.10
So within half a gram of each other.


After disassembling one slide, I compared the the weight of the old diaphragm to the new one.
old: 2.80 gr
new: 5.35 gr
Quite a difference.


More on re-assembly later.

[FlyingSteve]

Let us know if you find any difference in performance with the new rubbers. I don't think there will be unless you had lots of little holes/tears in your old ones.

[Nessism]

Good thread Greg. Please tell us what's involved with performing this repair - R & R details.

[Greg B]

Getting them apart

After marking the slide bodies so I can reorient the diaphragm tab correctly, I chucked the slides in the lathe & machined the flange that is rolled over to hold the diaphragm.

Careful. Don't want to cut too deep.

There, slide comes apart.

Four disassembled slides. And four brand new diaphragms. (Carb painting by RenoBruce)

[Guest]

This place is full of nerds. I have the same balance shown in message #1!

From the point of view of an erstwhile rubber chemist:

Some of the rubber in the diaphragms is plasticizers. They serve to improve ease and quality of manufacturing uniform parts, and to keep the part flexible in service. Over decades of use, gasoline vapors would be expected to leach away some of the plasticizers. But plasticizers are usually not anywhere near half the weight of most nitrile rubber compounds. Nitrile was the most likely material for the diaphragm when GSes were being made. Therefore, I suspect that nitrile has been replaced with a more modern, gasoline resistant rubber compound.The new diaphragms are probably thicker than the old ones, and should probably last much longer.

[TooManyToys]

But will the added weight affect the pulled height or response of the slides? But the full assembly weight and the percentage of this change by the diaphragms might be more telling.

[Greg B]

But will the added weight affect the pulled height or response of the slides? But the full assembly weight and the percentage of this change by the diaphragms might be more telling.

I thought about that. I'm probably going to need to make threaded retainers for the diaphragms, I think I will have to machine the ID of the slides to account for the excess weight.

[Nessism]

2.5 grams ain't jack. I wouldn't worry about it.

[srsupertrap]

Next step: How do you install & retain the new diaphragms?

[Greg B]

Back to it, at last.

The first thing I did was machine a split collar to grip the slide without damaging it.


Bored it, then tapped it 1"-32. Why the odd tap size you ask? Just one I happened to have, and it was a good size, leaving the slide walls plenty thick.



Machining some short threaded retainers. ( I cheated and used the CNC lathe at work for this op.)



Some RC680 Loctite.


Little pin spanner I made to tighten the inserts.


And there you have it. One re-assembled slide and NEW diaphragm. Only three more to go.

[Guest]

I have a bunch of ruined slides. Do you want them?

[posplayr]

OK this is motivating me to post some pics of my slingshot carbs mods

[Guest]

OK this is motivating me to post some pics of my slingshot carbs mods

DO IT!
Primitive but productive.

[bwringer]

Mmmkay, I don't see the point of this at all. What do the rest of us without access to free CNC machining do?

And who's the "guy in Australia" you got the new diaphragms from?

Or is this all secret because you're planning to offer slide rebuilding services?

Call me confused...

[Nessism]

Mmmkay, I don't see the point of this at all. What do the rest of us without access to free CNC machining do?

And who's the "guy in Australia" you got the new diaphragms from?

Or is this all secret because you're planning to offer slide rebuilding services?

Call me confused...

Amazing work here Greg. I'd be afraid to even ask how many hours have been involved with sorting though this mod or how much you would have to bill to do another set. Suffice it to say I applaud your skills.