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Gears are more like flat tappet cam and lifter, in fact you can think of gear teeth as little camsCirclotron wrote: ↑Sun Oct 14, 2018 8:32 pm Hypoid ring gear and pinion (where the pinion shaft is lower than the axle half shafts) have plenty of sliding motion and that's steel on steel. They seem to get along okay. Specific oil though.
GM's 4.2L I6 in the Trailblazers/Envoys runs the cams straight on the aluminum head with aluminum hold down caps, also. No bearings anywhere. Something I'm glad I didn't have to get into when the local machine shop overtorqued the caps so badly the cams barely turned. I knew something was up when the cam didn't roll over itself once I got over the nose from spring pressure. It just stayed there.Truckedup wrote: ↑Sun Oct 14, 2018 7:43 pmYeah, Ford N tractors ran the cam directly on the cast iron block..I believe the cam was cast, but not 100 % sure...On some manual transmissions, gears may spin on shafts with no bushings or needle bearingsexhaustgases wrote: ↑Sun Oct 14, 2018 7:39 pm So what about iron on iron? I've seen that a lot. And steel on iron as well.
Circlotron wrote: ↑Sun Oct 14, 2018 5:53 am Not quite an engine but the similarities are obvious.
A friend has a cheap, nasty and quite small air compressor that has an aluminum conrod with no bearing shells, just conrod running directly on the journal. When he first got it given to him free it had a huge big end knock. Eventually we found a replacement rod and all was well. The crank journal is about 1/2" diameter and was still smooth. If it quits again I am considering making a steel rod for it. Balanced be damned!
Is there any issue regarding running the steel rod on a steel crank pin provided the surfaces are sufficiently smooth to begin with?probably no issues.
Motorcycle rods and pins are almost all steel to steel and the same grade as well.
Triumph sixes did this too. It didn't work very well long-term. One of my friends had one where the cam dug itself so deep into the block that the hole was still egg-shaped after boring it out to take press-in bearings.Truckedup wrote: ↑Sun Oct 14, 2018 7:43 pmYeah, Ford N tractors ran the cam directly on the cast iron block..I believe the cam was cast, but not 100 % sure...On some manual transmissions, gears may spin on shafts with no bushings or needle bearingsexhaustgases wrote: ↑Sun Oct 14, 2018 7:39 pm So what about iron on iron? I've seen that a lot. And steel on iron as well.
I have yet to see any OHC engine with an aluminum head and separate cam bearings. They always ride directly on the aluminum. The spring loads are very low so this is not a problem.midnightbluS10 wrote: ↑Tue Oct 23, 2018 3:49 pmGM's 4.2L I6 in the Trailblazers/Envoys runs the cams straight on the aluminum head with aluminum hold down caps, also. No bearings anywhere. Something I'm glad I didn't have to get into when the local machine shop overtorqued the caps so badly the cams barely turned. I knew something was up when the cam didn't roll over itself once I got over the nose from spring pressure. It just stayed there.Truckedup wrote: ↑Sun Oct 14, 2018 7:43 pmYeah, Ford N tractors ran the cam directly on the cast iron block..I believe the cam was cast, but not 100 % sure...On some manual transmissions, gears may spin on shafts with no bushings or needle bearingsexhaustgases wrote: ↑Sun Oct 14, 2018 7:39 pm So what about iron on iron? I've seen that a lot. And steel on iron as well.