derporsche928

I was reading this in hard copy last night at work, (had a picture of the bearing in the mag....) and thought it looked like an interesting thing to explore for our cars...... Less friction, lower lubricant requirements......
Zinggggg.....

http://wardsautoworld.com/ar/auto_ti...earings_boost/

Jim M.

A looong time back (showing my age now ) Crane cams offered a roller bearing set up for their cams. It was supposed to greatly reduce the force required to turn over an engine. The applications were for mostly American cars with pushrods. Aircraft engines, both jet and the older piston engines used roller bearings for their primary bearings (crank bearings on the recip's).

To bad it couldn't be retrofitted to our engines!

Jim Mayzurk
93 GTS 5-spd

Imo000

Friction bearings have a much larger surface area and technically when under oil pressure, they have very little to no friction at all. The violent forces generated by the con rods can limit the bearing design. I don’t think anything but the existing friction bearings will work.

If this would work and safe fuel, F1 teams would have been all over this by now.

6.0-928S

That was Crower. They called them their 'Imperial' series cams.
Regards, Hammer

Fabio421

Porsche used roller bearings on the crank in one version of the 356.

Mike Simard

Roller bearings in the crank and rods have been attempted since the early days of cars. Some notable ones are the pre war Auto Unions. the normal tendency is to stop using them once tried. There are some advantages to plain bearings over rollers aside from complexity. There's at least one modern F1 engine that tried rollers, I'm not sure which, maybe a Japanese one? The latest trends have rollers being replaced with plain bearings even in places where it's not a complex installation. Ducati did some testing on valvetrains used in race bikes and wound up going to plain bearings after learning stuff, they have an ability to deal with shock and vibration superior to rollers.

dr bob

I have a little experinece with roller-bearing cranks. The Big Danger on them is that ANY detonation will flatten the rollers and make a crank into junk in a hurry. The cranks are assembled from multiple sections that are pressed and sometimes pinned together, then the crank or locating pins are tack-welded carefully so the pins don't turn in the throws. Once assemble, the cranks are not rebuildable, so when detonation does damage the rollers, or a hard torsional impact causes the crank to twist and lose index, the only option is new crank assembly. Lubrication of the bearings is then by oil mist in the crankcase, generated by grooves cut into the edges of the mains. Mains are conventional pressurized bearings, and the oil that escapes generates the fog that lubes the rod-end rollers. A crankcase filles with oil mist on purpose means that ANY blowby will tax the oil separator and recovery system. Obviously a dry sump is the preferred lube method, but the scavenging pump needs to draw liquid from the bottom of the sump, and can't pull any vacuum at all.


Remind me why we were thinkin of this as an option?...

Mike Simard

Bob, what kind of engine did you work with?

BTW, another disadvantage to rollers is sudden rpm changes, if the rollers can't accelerate fast enough they would drag.

Formula94lt1

maybe a roller thrust bearing....

dr bob

Mike--

I built a few Porsche and VW 4-cyls with roller cranks. Heavy & lots of rotating mass so great launches, but heavy & lots of rotating mass so slower to accelerate them too. Also have some time in with the 2- and 4-cyl Yamaha 2-strokes in my little race car and bikes. I've done a little tuning on other roller race motors too over the years.

The "can't accelerate fast enough" isn't a problem. They -will- accelerate fast enough or they will float on a film of oil that takes up the clearances. On the scooter motors, they work great until you burn a piston, twist a rod ever-so-slightly, or cause any detonation from any other reason. Then you can use it to keep your boat from floating away; those small-end bearings are a handy place to loop the chain...

GregBBRD

In theory, a plain bearing never touches the crankshaft, as it rides on a film of oil. A roller bearing has to touch the crank and thus actually has more friction. Besides that, the crank pins have to be very, very hard, as they act as the bearing race. This is one reason that roller bearing cranks are multiple pieces.....and huge dollars to built. Usually the rods are one piece, also. This is also so they can be very hard.

69gaugeman

Being in the tool and die industry for many years I always wondered if you could not make a crank out of D2 or something similar and have it heat teated then make some rods from similar material and do a two piece con rod. There are roller bearing that use two piece construction to allow installation in the middle of a shaft.

I will have to look it up again but plain bearings do have more friction than roller bearings of the same size. If you have ever seen the old VW roller cranks that were around WAY back, they would rev up soooo much faster than a plain bearing one. But detonation or lugging the motor took the crank out of index and made a big pile of scrap quickly.

derporsche928

I guess that'd be my fault, as I started the thread.... Sorry, I just thought it was interesting..... I know it's been done over the years on various motors..... I believe it kind of started on 2 cycle motorcycle engines, and seeing it come back around in a well respected manufacturing mag caused me to have a brain fart....

I hear you too Sterling..... Perhaps we should let this thread die a slow and agonizing death, and get back to more viable engineering alternatives like variable valve timing......

Peace,

derporsche928

Hey Gaugeman,
I've been in the Tool and Die trade for a long time myself......
I see you're from Windsor.... I don't suppose you do any mold work for Toyota, as we have several vendors up that way?

Best,

69gaugeman

Was in tool and die in Vancouver. Moved here and got involved with cutting tools and now for the last 14 years in gauging.