Calculating journal bearing oiling requirements

[dannobee]

Mahle has a white paper on this stuff too. Cylinder Components.

https://link.springer.com/content/pdf/b ... -1%2F1.pdf

[RDY4WAR]

i rebuilt a Jr johnson built BBC that had .060 rod side clearance but the rods were located by the pistons on the small ends. doing it this way means the oil flow which cools the bearings passing thru rod bearing is consent

The oil doesn't actually cool the bearings. The majority of bearing heat comes from hydrodynamic friction of the oil film itself. Even the rod bearings only see ~3% of combustion heat. It's why bearing temps increase with higher viscosity and why oil doesn't warm up much from idling on a cold morning.

The sense of cooling is through preventing excessive heat from being generated to begin with.

[ELS]

If you already have all the answers about this, then why are you asking this question ...?
Probably because you are trying to find justification for what you think ...?
Sorry, I rained on your parade.

what?
so because I ask, that means I know the answer already?

NO, not at all ... because you attempt to argue with an answer shows this to be. If you don't like someone's answer, just forget it.

so for example if someone tells me the earth is flat, and I havent tested it myself. is it wrong to argue about it to try to understand how they came to this conclusion? do I rather ignore them and let them continue telling everyone this when they probably misunderstood something in their math or whatever?

I dont agree at all with "if you dont like an answer, just ignore it"... thats just being ignorant

[Walter R. Malik]

what?
so because I ask, that means I know the answer already?

NO, not at all ... because you attempt to argue with an answer shows this to be. If you don't like someone's answer, just forget it.

so for example if someone tells me the earth is flat, and I havent tested it myself. is it wrong to argue about it to try to understand how they came to this conclusion? do I rather ignore them and let them continue telling everyone this when they probably misunderstood something in their math or whatever?

I dont agree at all with "if you dont like an answer, just ignore it"... thats just being ignorant

If you asked them a question about the the Earth and wanting information but, got an answer you did not agree with ... then an ensuing argument is showing the ignorance, not the other way around. They didn't ask you for anything ... you "asked" them.

You are not expected or required to agree or not.
By simply asking the question, hopefully your goal was not to kibitz but, to learn and forward you own education.

Apparently, you just can't understand that.




...

[ELS]

NO, not at all ... because you attempt to argue with an answer shows this to be. If you don't like someone's answer, just forget it.

so for example if someone tells me the earth is flat, and I havent tested it myself. is it wrong to argue about it to try to understand how they came to this conclusion? do I rather ignore them and let them continue telling everyone this when they probably misunderstood something in their math or whatever?

I dont agree at all with "if you dont like an answer, just ignore it"... thats just being ignorant

If you asked them a question about the the Earth and wanting information but, got an answer you did not agree with ... then an ensuing argument is showing the ignorance, not the other way around. They didn't ask you for anything ... you "asked" them.

You are not expected or required to agree or not.
By simply asking the question, hopefully your goal was not to kibitz but, to learn and forward you own education.

Apparently, you just can't understand that.




...

Oh, I didn't know asking more than 1 question was frowned upon.

gee it seems that asking shit on forums is useless unless it is like "what's 1+1?"... impossible to get an answer, just hate.

[modok]

Remember you aren't the only one watching.
After the ego battle is over let me know, then we can get back to in fixing the problem.

[Tom68]

They're self limiting, even in a fullu grooved bearing the oil has to try and force past a 2, 2 thou x around 7'' gap.
Oil pressure relief valve take care of the excess oil flow from the pump that's sized to keep all pressure to all parts even in a well worn engine. All you need is pressure in the main gallery and you have even distribution.

[juuhanaa]

I dont know is this of topic, but two small things i found from a rally engine (builder made a spare incase it is needed in future ---> good thinking)

Some reason what i dont know, the surface where we measure the side clearance, has not been machined like in the bearing housing. The bearings are similar to some diesel engine? Im guessing it is to increase rod strength, but maybe some one know better does it have affects to oiling requirements? I have no idea,

Screenshot_20220623-232600.jpg

-juhana

[Walter R. Malik]

Remember you aren't the only one watching.
After the ego battle is over let me know, then we can get back to in fixing the problem.

OK, modok ... one more time; maybe a bit clearer this time.

You can never have to much oil flow "to a plain bearing" which uses a hydrostatic wedge to survive ... NEVER.
Allow the journal circumference and bearing clearance, (along with the oil pressure), to regulate the oil "leaving" the bearing.
Oil is a cooant along with delivering the lubrication.

The only reason to limit oil volume going anywhere in an engine is to make certain the bearings always get enough oil. Some people like to run smaller volume oil pumps than normal and enough oil volume to the bearings is paramount.

Maybe there are oil burning or leakage issues somewhere but, that is a different problem altogether.

[modok]

I agree, and I expect you would agree generally with my initial suggestion.
Although say a rocker does not need to be even a full circle so what is the clearance of that are then?
But without more details of exactly what this driveshaft thing looks like and does, It's hard to say for sure.
Maybe that's not the question tho it could be the answer
If you can put the oil feed just upstream of the loaded zone in an area the clearance remains about the same as it wears, then it can wear and not change how much oil flows.

Or another way you can look at it is relative terms say.... the oil pump produces a volume per rev, or a pressure, and how much of that oil goes to each bearing depends on the SIZE of oil feed to it as compared to all the other bearings. Usually "the curtain area" of the oil feed hole. Tho at small clearances I think it ends up non linear to area...not just like a carburetor jet....but at larger gaps it might.

Lots of ways to solve a problem.
The required oil flow could be "calculated" in a lot of different ways too I bet depending on how you define that, some estimation of load? Or just leakage? I can't be much help there.

[modok]

picture of rod with cheeks blasted

-juhana

They shot blasted the sides, just because being lazy. Some would say it isn't very important enough to worry about.
But if it was maximum effort then it should be ground smooth.

[fabr]

The shot blaster sides would not bother me at all. The important thing is enough side clearance. Rule of thumb I read of is 4X bearing clearance = MIN side clearance that will not heat the oil beyond what the oil absorbs from journal/bearing and the oil from friction of the oil itself with itself. I think most would shoot for 1.5X though. (.003X4=.012X1.5=.018 side clearance minimum) I do anyway. ANYTHING beyond that is good to go.

[modok]

And just to be clear we are talking about oil flow to an "oil pump driveshaft bearing" right?
I read the first post twice but still not 100% sure.

[fabr]

And just to be clear we are talking about oil flow to an "oil pump driveshaft bearing" right?
I read the first post twice but still not 100% sure.

I may be wrong but I didn't take it that way.

[Tom68]

And just to be clear we are talking about oil flow to an "oil pump driveshaft bearing" right?
I read the first post twice but still not 100% sure.

If he wants to restrict bearings in a series I'm assuming mains to look after his apparently vulnerable oil pump drive shaft ???????????????????? But I'm sure I'm wrong.