John Riley wrote in message
...
Could someone point me to some information about what metals I could use
for
king pin bearings on a small, electric-motor-assisted, adult trike I'm
planning to build?
I was thinking of a tubular, square, thickwalled aluminum axle, and two
mild
steel plates bolted top and bottom to each end of this with holes bored
top
and bottom and a thick aluminium rod turned to fit into the holes of these
plates (trunnions?) and then be drilled and tapped at the correct angles
for
the M12 HT steel bolts for stub axles.
In other words, with good lubrication, is aluminium rod OK in steel
bushes?

Aluminium in mild steel is about the worst combination I could envisage,
especially with the possibility of dirt ingress. Poor friction coefficients,
rapid wear and galvanic corrosion are just some of the issues. Hardened
steel in aluminium bearings is ok if the system is enclosed and well
lubricated such as inside an engine, camshafts and piston gudgeon pins being
examples. King pins are usually case hardened steel pins in bronze bushings
or roller bearings with dirt seals at each end and provision for lubrication
via grease or oil nipples.

You'd never choose aluminium over steel for a load bearing axle or pin
anyway. Why go for a soft weak material over a hard strong one?
--
Dave Baker