Vulcanizing: what is it? (A-arm rebuild with OEM rubber)

[Jdub]

Hey gang:

What exactly is vulcanization? If memory serves me, it is a process of "attachment via heat." Does this seem correct, or is there a heat/chemical combination that results in the best adherence?

In this case I have secured a set of rubber bushings for the front A-arms of a '78SC and I will be putting them in shortly. I'd like to know if an interference fit is going to be enough to keep the bushing from rotating within the confines of the "outer' and "inner" A-arm.

Thanks in advance,
John

[724doorE]

Ahh... I belive this process is credited to some guy named Goodyear. It is the chemical process of replacing the double bonds found in natural rubber with bonds that cross link the polymer chains via the S atom. The previous double bonds are unstable and contribute to poor tensile strength and what we call dry root, a breaking down of the structure. What are you planning on vulcanizing!



Dennis H.

72 911E

[Jdub]

Hold cow Dennis! This board amazes me: everything from Pinewood derby tactics to this post!

The A-arm bushes are vulcanized to the A-arm proper; that is the technique I am seeking to either replicate with these new rubber bushes or, failing that, resolving the question "is it really necessary to vulcanize the bush to the A-arm?"

That's it in a nutshell. Will an interference fit work fine, or is it time to break out the fire, glue, or whatnot to force the bush to adhere?

Thanks,
John

[Jim Sims]

I believe what this means is the rubber was molded and polymerized in place within the tube in the arm. I suspect there is a good bond to the steel but it likely isn't "polymerized" to the steel. Although not as good as molding in place, a tight fit with a glue is certainly better than a sloppy, rotten bushing. The harder plastic bushings work and they're not molded in place. Replaceable rubber bushings are apparently available for the 914 and I think also for the SWB 911? I may misunderstand the design, but I suspect the important issue is that the rubber not rotate within the tube in the arm and become worn as a result. I intend to rebuild some front A-arms this same way. Where did you get your bushings? If they're OEM can you share the part numbers?
Thanks, Jim

[724doorE]

Ahh, gentleman, I wasn't intending to infer that the rubber was polermerized to the metal. I was defineing the process of vulcanization as it is used to improve the properites of natural rubber. The process merely affects the rubber. Natural rubber has double covalent bonds between carbon atoms in a single chain. They cause the aforementioned trouble. Vulcanization basically replaces those double bonds with so called cross linking bonds between chains via the sulfur atom.


This is relating to NATURAL rubber and was the original use of the process. And yes heat is involved! The term seems to be commonly used now to describe applications such as the bushings that are molded in place. If you care to look in a few text books, you'll find a more thorough description than I just gave. Check it out!

I doubt that your bushings are natural rubber-- They are synthetic-- also a polymer but a manmade one.. I was merely attempting a play on words-- It didn't work!

Dennis H.

72 911E

[ebrownson]

Who here thought it had something to do with Spock?

Eric
83SC

[turbo dave]

Okay, so on a completely mundane level...

What bushing do you'all recommend for the spring plate? I'm pushing the car towards the DE/auto-x direction, but I've heard good things about Neatrix rear bushings. I realize urethane bushings squeek, but would I notice a much tighter feel to the rear suspension with them, or are the Neatrix okay?

[Clark Griswald]

Performance Products was planning on offering Neatrix (rubber) bushings for the front control arms, but aborted those plans. The reason they gave me for canceling this was that the non-vulcanized rubber left the front end feeling "scary".