Circlotron 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.
Gears are more like flat tappet cam and lifter, in fact you can think of gear teeth as little cams
Perhaps a needle roller or ball bearing, is more similar to a gear than a plain bearing.
I opened up an engine someone had free floated the pins on... Never used a bushing on the rod. Had a lot of miles, and wasn't worn. Piston pin against the rod.
exhaustgases 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.
Yeah, 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 bearings
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.
JC -
bigjoe1 wrote:By the way, I had a long talk with Harold(Brookshire) last year at the PRI show. We met at the airport and he told me everything he knew about everything.It was a nice visit. JOE SHERMAN RACING
Had the exact same thing with a Harbor Freight compressor on which a flex hose blew off late one night so the poor thing tried to refill its 60 gallon tank all night & overheated. I looked at the no-oil-pump design and made a new con-rod out of scrap 7075 aluminum. Took about 1/2 hr and that was 4 years ago. My best guess- don't screw around with steel on steel when its so easy to dup' the rod in other materials; if I'd had a chunk of bronze, I'd have used that.
Ball and roller element bearings are friction-less bearings ,journal bearings are passing surface bearings for lack of a better description and need constant supply lubrication.
could it be that plain bearing cranks are a cheaper way to do crank journals. porsche built engines with roller bearing cranks and motorcycles also had roller bearing crank journals
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.
exhaustgases 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.
Yeah, 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 bearings
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.
exhaustgases 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.
Yeah, 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 bearings
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.
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.
when GM came out with the mercury marine built 4 cam engine for the corvette they had problems with the cam running directly on the aluminum head. that is why they switched to mobil 1 oil which flowed better when cold and solved the problem