Acetal on acetal bearing. Will it work?

[cadastrophe]

I have been offered a quantity of surplus acetal top hat style bushes that I am considering using for suspension pivots. The drawback is, the ID is quite large and I do not want to use a large internal steel bush because they will weigh too much.
For lightness, can I use acetal for the internal bush too(supported by a class 10.9 bolt) and operate the top hat bush on that?
Would the acetal on acetal cause to much stiction? If it is OK can anyone suggest running tolerances?

 

[patprimmer]

Nylon on acetal gives a much better bush than acetal on acetal. If it is graphite and molly filled nylon that is even better. If it is PTFE and silicone oil modified acetal even better still, but I guess your stuck with what you have.

I have no idea of actual tollerances, other than to say that acetal shackle bushes I have used on the rear suspension of a 3/4 tonne V8 powered, passenger car based van, had a non rattle but slightly loose slip fit, I guess about 0.002"clearance on a 7/16"or 1/2" pin. It was a long time ago, so I don't remember exact dimensions.

Regards
pat pprimmer@acay.com.au
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[dwightdixon]

The reducer bushing should be nylon for the above reason. If you use Glass filled nylon and macine it to get the right diameter you will have truble because you will expose the glass causing wear. Depending on the application you might experience swell of the nylon when it gets damp so figure the running clearence based on how much swell you may experience. If it is not exposed to moisture or you measure a swelled part, then 0.002 would be the minimum. Looser fit would just make fit sloppy and that may not affect function. Depending on what the RPM and load of the application is, you could get into heat problems. Consult the Dupont design guide for PV limit calculations. Adding lubricant (via grease when assembly) or built in lub, it depends on how much torque loss you are willing to accept, and whether wet lub will be dirt collector.

Lots of things to consider and take account for in your decision.