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Bush material
chrisf - 13/4/04 at 08:32 PM

Hi all:

I'm looking to use PU in a 95A durometer, Delrin AF or UHMW in a 67D hardness. I especially like the UHMW because of the price, but know little about it. Has anyone used this stuff for bushings?

I want to buy the bush material in bar form and lathe it down. Any guidance is appreciated.

--Chris

andkilde - 13/4/04 at 10:10 PM

Hey Chris, I sell plastic for a living so may be able to help a bit.

PU in 95A is fairly machinable and quite suitable for bush use.

Delrin has excellent machining properties is not hydroscopic (A very good thing -- Nylon absobs water and can "grow" up to 10%, a very bad thing in a bush).

UHMW machines "messily", makes nasty stringy shaving that can be a PITA, and can get a bit "mucky" if you take a big pass at it and it gets too hot. Machined carefully it's OK though.

Good Luck, Ted

Rorty - 14/4/04 at 01:38 AM

I fully agree with andkilde, and I have a few other points worth considering.
PU bushes will require initial and subsequent lubrication with molydisulphide grease.
Acetal works best if assembled with moly grease, but doesn't require the same degree of periodic maintenance.
Consider PU as a flexible (marginally if you're using 95) material that will comply with slightly out-of-line sleeves or brackets.
Acetal on the other hand is best thought of as an unforgiving metal, and will therefore also produce the harshest ride.

chrisf - 14/4/04 at 12:57 PM

I understand that the UHMW is not UV stable. But as I understand it, these bushes will no sit in direct sunlight.

Is the Acetal UV stable?

I'm not exactly looking for a terribly harsh ride, but want to use the most cost-effective plastic as possible. I'll try the UHMW and let you guys know how it turns out.

--Chris

andkilde - 15/4/04 at 03:58 PM

quote:
Originally posted by Rorty
Acetal on the other hand is best thought of as an unforgiving metal, and will therefore also produce the harshest ride.


Hi Rorty, a little off topic but, I've always wondered a bit about the "harshness" factor.

Some folks say that spherical rod ends can actually make a car ride better since the suspension pivots more freely than with bushes. And, properly fitted and lubed, plastic bushes "should" be more free than metalastic bushes.

As you've used all of the above on your projects, do you have some gut feelings on the subject?

Cheers, Ted