Carbon as bushes/bearings

[geoff p]

I'm building an experimental horizontal petrol-engine, incorporating some unusual (?) ideas. I reckon that the power will be very low so I hope to get away with non-full-size materials.

The crankshaft is machined from an aluminium casting, with main bearings in ball-races. I would like to try carbon for the big-end bushings, on the basis that electric-motor brushes run for sometimes years rubbing against the copper commutator.

Have any of you had experience of using carbon rubbing against aluminium, with or without lubrication?

I have read that some flame-licker designs use a carbon piston in an ali. cylinder though I guess the forces there a quite different from what I want to do.

Geoff

 

[b.lindsey]

INteresting question Geoff. A quick search through McMaster, doesn't turn up any pure graphite bushings, they do show a graphaloy compound which contains some copper for strength. I am sure some of the more experienced IC members will have some thoughts but I think you are probably right in that the forces acting on bushings vs. a piston are totally different...and in a gas enginethe forces of compression and ignition would be transmitted through the crankshaft putting greater side forces (radial) on certain segments of the bushing ID. As you note, graphite can wear well, but it is brittle. I am interested in what answers others have now too!!

Bill

 

[Herbiev]

I'm with Bill on this one. I dont think carbon would do the job. Graphite gives a lot less friction and an alloy for the strength