Roller Bearings for Opel Engines?

[jeff denton]

Originally Posted by Tru-Craft Ever think about trying to machine the Opel engine for roller bearings? I'm sure you have!

Like a two cycle outboard boat motor. Sure, why not? That's Sixties technology. Must be a reason it hasn't been done in car engines.

[Tru-Craft]

Originally Posted by jeff denton Like a two cycle outboard boat motor. Sure, why not? That's Sixties technology. Must be a reason it hasn't been done in car engines.

Jeff, I always wondered why also.
Probably cost and too much load for the bearing surface area.
I know F1 cars are doing it, 19,000rpm's!
The Opel castings are probably not thick enough to put sleeves and roller bearings in anyway's.
Lyle

[RallyBob]

Originally Posted by Tru-Craft The ultimate friction reducer..........roller bearings! Ever think about trying to machine the Opel engine for roller bearings? I'm sure you have!

I definitely have thought about it, even WAYYY back when I started out with Opels. Then I remembered reading that the flat-4 Porsche Carrera engines from the mid/late 1950's had all roller bearings, and they took something like 60 hours to assemble. And if they were allowed to operate for sustained periods below 4000 rpms the needle bearings would fail due to lack of oil, etc.

A lot of modern bike engines use needles, but they have bolt-together crankshafts which makes it a lot easier to assemble with a caged bearing assembly rather than loose needles!

I'm sure the cost would not be low either, at least in terms of machine work and heat treating. I suspect the crankshaft and associated surfaces the needles ride on would all have to be of similar hardness? The needle bearings themselves would be the cheapest part of the experiment.

Bob

[namba209]

I'm a little late on this, been outa town. One thing I learned during my A & P Engine class, Roller and/or needle bearings won't last in a large reciprocating engine. The compression and firing loads will flatten them if used in the big rod end. They may be O.K. to use on the crank, because the loads are transmitted through the length of it. I imagine they would work idf the engine is continually above 10K RPM, like my model boat engines. Although they are used in the small motorcyle engines, but there again the RPMs are much higher than in cars. Just thought I'd pass that info on.

[wrench459]

Originally Posted by namba209 One thing I learned during my A & P Engine class, Roller and/or needle bearings won't last in a large reciprocating engine. The compression and firing loads will flatten them if used in the big rod end.

Ron help me out with this one
I'm not sure is the recip. mass or the rotating mass thats giving the problems or the bearing speed. I'm leaning on the bgr. speed large journal cranks have crazy bgr. speeds. Now if we keep the journals as small as possible then needle bgrs might work.
Talk about thread creap we go from a bad ace header to the crankshaft.

[namba209]

Actually, it's the reciprocating mass that causes the problem. Think of the piston and rod combo as being a jackhammer on the crank journal. With shell bearings the impact loads are spread around the journal, whereas with a needle or roller only a very small pencil line is where the impact loads are at. Because that's all the area the needle or roller will have on the journal. So they eventually will flatten out and the bearing is destroyed along with the journal. At least that's what my instructor told us, and if you think about it, he's right. It's the ol' bed of nails trick, you can lay on a bed of nails, but try standing on just one, pointy side up and it'll go right through you. It's the old area/pressure rule, more area, less pressure. Using this same scenario, needles will work much better in a rotating mass, because of less friction from less area scrubbing on the bearing journals. You're right about this going off topic, too. Sorry Bob.

[wrench459]

Originally Posted by namba209 Actually, it's the reciprocating mass that causes the problem. Think of the piston and rod combo as being a jackhammer on the crank journal. With shell bearings the impact loads are spread around the journal, whereas with a needle or roller only a very small pencil line is where the impact loads are at. Because that's all the area the needle or roller will have on the journal. So they eventually will flatten out and the bearing is destroyed along with the journal. At least that's what my instructor told us, and if you think about it, he's right. It's the ol' bed of nails trick, you can lay on a bed of nails, but try standing on just one, pointy side up and it'll go right through you. It's the old area/pressure rule, more area, less pressure. Using this same scenario, needles will work much better in a rotating mass, because of less friction from less area scrubbing on the bearing journals. You're right about this going off topic, too. Sorry Bob.

IMOA the load area of the bgr. is very small mostly on the top.
How about thinking of wheel bgrs. what supports the car the full bgr or just a small area of the bgr.?
Just thinking out loud thats all.

[namba209]

Originally Posted by wrench459 IMOA the load area of the bgr. is very small mostly on the top. How about thinking of wheel bgrs. what supports the car the full bgr or just a small area of the bgr.? Just thinking out loud thats all.

Actually, that's scary to me. Think about all those 18 wheelers and what they weigh. All that weight is on the bottom of some tiny tapered roller bearing when it's at a stop. But when it's rolling, the wieght is transferred to each succeeding roller as it rotates around. Like I said, it's scary, and a good reason not to neglect them.

[jeff denton]

If you want to see this theory for yourself, I'll describe a way to prove it.
Check the tapered wheel bearing race (called the "cup" in a truck shop) that came out of the hub of a very heavy rig that had just been hauled a good distance on a lowboy (very heavy duty trailer). You can see where each roller had pounded it on the bottom. It won't last long. That's one of the reason even a light car should be hauled "blocked up". Bearings have to be spinning to carry the load and get lube.

[markandson]

The other thing about sleeve bearings is that when the crank is rotating inside it, it is carrying a wedge of oil with it which is really why the bearings don't wear out you are not resting on the metal at all, it is rotating within a thin hydraulic wedge of oil. This condition also spreads the load over a much larger area of the bearing during the power stroke.

[wrench459]

Originally Posted by markandson The other thing about sleeve bearings is that when the crank is rotating inside it, it is carrying a wedge of oil with it which is really why the bearings don't wear out you are not resting on the metal at all, it is rotating within a thin hydraulic wedge of oil. This condition also spreads the load over a much larger area of the bearing during the power stroke.

Thank you very much Jeff for bring this subject up.
Without the hydraulic effect our engines would not last very long.
But theres always a but most of the time its me
Questions
1 how much of the load is spread where on the rod?
2 Where does the rotating mass separate from the reciprocating on the rod?
Weighted a rotary rotor today only one.. with parts missing would you believe 5300 grams I'm no Mazda expert but I believe theres needle bgrs available.. eyeballing the journal 2.5 inches
Sorry Bob for highjacking the thread

[namba209]

Originally Posted by wrench459 Questions 1 how much of the load is spread where on the rod? 2 Where does the rotating mass separate from the reciprocating on the rod?

Actually it's very easy to visualize. The rod and cap are always close to centered on the rod journal, so the loading is real close to rod centerline either on the upper shell or the lower shell. It depends on what the piston stroke is. The rod is pushing down on the journal or it's being pushed or pulled on the journal.

I'm not sure if there is a definitive area where the reciprocating mass ends and the rotational mass begins. Maybe someone with more expertise can assist you there.

[kwilford]

Moderator Note: So far off-topic I can't SEE a SportWagon! Posts split to new thread...

[tomking]

Well Keith! Dont sportwagons use bearings too?

[namba209]

Originally Posted by kwilford Moderator Note: So far off-topic I can't SEE a SportWagon! Posts split to new thread...

Thanx Keith, I was gonna ask you or one of the other mods to do this, it has gotten way off what Bob has in his thread.

[Gumby]

Roller bearings are not a new thing... as others have stated durability, complexity, and cost are all good reasons why not to use them in the crankshaft. Why complicate the equation when plain hydrostatic bearings do just fine?

A good example is the spindle head of a milling machine. I can't think of a single industrial (CAT40 or larger) mill that has roller bearings in the spindle. Most of the high end machines used in high speed machining use either air bearings or plain fluid bearings and some even use high powered magnetic bearings. If you want to spin something at 10k - 20k rpm or more under load you simple don’t use roller bearings, there are much better options.

Besides a slight reduce in startup friction what would you be trying to gain out of using roller bearings?

[guyopel]

Early Saab 's had roller and ball brg. crankshafts ( three cyl. eng. that was also a 2cycle ) and was able to run at 9k to 12k on the high output racing eng.
John

[jeff denton]

Originally Posted by kwilford Moderator Note: So far off-topic I can't SEE a SportWagon! Posts split to new thread...

But, I didn't start it! I think Lyle did.

[namba209]

Shell bearings or bushings work very well where the application has radial loads imposed. When there are no radial loads a tapered roller or ball bearing work better. They require less lubricant and have very low rolling resistance. A case in point are the bearings in turbochargers. They spin over 100K RPM and only need a continual mist of oil to keep them happy. In my model boat racing engines, the crank runs in ball bearings with bushings on the rod ends. The only lubricant is a 15% mixture of oil in the fuel, and they turn upwards of 30K RPM.

[Gumby]

I doubt the roller bearings had anything to do with the Saab engine's ability to rev to 12k rpm.

It seems like most engines in the 60s that used roller bearings were small. I am sure there are exceptions but as namba said earlier about the rotating mass… the larger the engine, the more iron/steel that is getting slung around and the forces on the bearings become larger which can mean flatted bearings. Scaling an engine design doesn't always work so well. Sure you can build a model wankel engine with no seals but it doesn't work so well in a larger engine.

I've seen model engines made with plain bearings and no oil system either that lasted many years of har