Calculating journal bearing oiling requirements
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Calculating journal bearing oiling requirements
I want to calculate the ideal oil flow to a journal bearing, is there a formula or calculator that I can use?
also subquestion related to this; would it be a good idea to then install restriction jets to the oil pump side of the main bearing oiling holes? as to equalize oil flow to the main bearings?
also subquestion related to this; would it be a good idea to then install restriction jets to the oil pump side of the main bearing oiling holes? as to equalize oil flow to the main bearings?
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Re: Calculating journal bearing oiling requirements
You are never going to have to much oil going to a journal ... allow the bearing clearance to regulate the amount of flow.ELS wrote: ↑Sun Jun 19, 2022 9:27 am I want to calculate the ideal oil flow to a journal bearing, is there a formula or calculator that I can use?
also subquestion related to this; would it be a good idea to then install restriction jets to the oil pump side of the main bearing oiling holes? as to equalize oil flow to the main bearings?
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Re: Calculating journal bearing oiling requirements
GPM = 29.3 x 10^-9(L + .0043(W/D))mD^2N
D = journal diameter (in inches)
L = bearing width (in inches)
m = bearing clearance factor
N = rotational speed
W = bearing load (in pounds)
This will get you your minimum. However, as has been stated, you can't really have too much. There's no benefit to restricting oil flow to a bearing. The viscosity of the oil is the bigger factor as you need a minimum oil film thickness to withstand the bearing load. The wider the clearance, the more viscous the oil needs to be.
D = journal diameter (in inches)
L = bearing width (in inches)
m = bearing clearance factor
N = rotational speed
W = bearing load (in pounds)
This will get you your minimum. However, as has been stated, you can't really have too much. There's no benefit to restricting oil flow to a bearing. The viscosity of the oil is the bigger factor as you need a minimum oil film thickness to withstand the bearing load. The wider the clearance, the more viscous the oil needs to be.
Re: Calculating journal bearing oiling requirements
too much oil causes excessive friction (but not wear).Walter R. Malik wrote: ↑Sun Jun 19, 2022 10:47 amYou are never going to have to much oil going to a journal ... allow the bearing clearance to regulate the amount of flow.ELS wrote: ↑Sun Jun 19, 2022 9:27 am I want to calculate the ideal oil flow to a journal bearing, is there a formula or calculator that I can use?
also subquestion related to this; would it be a good idea to then install restriction jets to the oil pump side of the main bearing oiling holes? as to equalize oil flow to the main bearings?
and I'm not thinking of reducing oil flow to the mains, just to equalize them. the reason I'm asking for a formula to get the minimum required oil flow to a journal bearing is because in my engine design, if the oil pump drive shaft journals wear even a little bit, oil pressure suffers a lot, (dropping to around 0.4bar pressure at idle, around 2bar at redline)
this is because the supply to this journal bearing is straight from the oil filter and trough a 4mm hole as a restriction, then the oil needs to do a 90 degree turn to get to the main oil gallery
to fix this I will be tapping a carburetor fuel jet in this 4mm hole, but I want some guideline to what size of jet I will put in it, I don't want too little to cause premature wear, nor do I want too big which then defeats the purpose.
Re: Calculating journal bearing oiling requirements
what measurement is the rotational speed in? in RPM, Ft/s, m/s?RDY4WAR wrote: ↑Sun Jun 19, 2022 11:47 am GPM = 29.3 x 10^-9(L + .0043(W/D))mD^2N
D = journal diameter (in inches)
L = bearing width (in inches)
m = bearing clearance factor
N = rotational speed
W = bearing load (in pounds)
This will get you your minimum. However, as has been stated, you can't really have too much. There's no benefit to restricting oil flow to a bearing. The viscosity of the oil is the bigger factor as you need a minimum oil film thickness to withstand the bearing load. The wider the clearance, the more viscous the oil needs to be.
Re: Calculating journal bearing oiling requirements
RPMELS wrote: ↑Sun Jun 19, 2022 11:54 amwhat measurement is the rotational speed in? in RPM, Ft/s, m/s?RDY4WAR wrote: ↑Sun Jun 19, 2022 11:47 am GPM = 29.3 x 10^-9(L + .0043(W/D))mD^2N
D = journal diameter (in inches)
L = bearing width (in inches)
m = bearing clearance factor
N = rotational speed
W = bearing load (in pounds)
This will get you your minimum. However, as has been stated, you can't really have too much. There's no benefit to restricting oil flow to a bearing. The viscosity of the oil is the bigger factor as you need a minimum oil film thickness to withstand the bearing load. The wider the clearance, the more viscous the oil needs to be.
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Re: Calculating journal bearing oiling requirements
What have I done wrong?RDY4WAR wrote: ↑Sun Jun 19, 2022 11:47 am GPM = 29.3 x 10^-9(L + .0043(W/D))mD^2N
D = journal diameter (in inches)
L = bearing width (in inches)
m = bearing clearance factor
N = rotational speed
W = bearing load (in pounds)
This will get you your minimum. However, as has been stated, you can't really have too much. There's no benefit to restricting oil flow to a bearing. The viscosity of the oil is the bigger factor as you need a minimum oil film thickness to withstand the bearing load. The wider the clearance, the more viscous the oil needs to be.
► 29.3 * 10^-9 * (.5 + .0043 * (1000 / 2.2)) * .002 * 2.2^2 * 9000 = 6.2655119999999999E-006
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http://www.magneticlynx.com/carfor/carfor.htm
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Re: Calculating journal bearing oiling requirements
clearance factor is too low, it is the clearance / diameter * 1000Stan Weiss wrote: ↑Sun Jun 19, 2022 12:33 pmWhat have I done wrong?RDY4WAR wrote: ↑Sun Jun 19, 2022 11:47 am GPM = 29.3 x 10^-9(L + .0043(W/D))mD^2N
D = journal diameter (in inches)
L = bearing width (in inches)
m = bearing clearance factor
N = rotational speed
W = bearing load (in pounds)
This will get you your minimum. However, as has been stated, you can't really have too much. There's no benefit to restricting oil flow to a bearing. The viscosity of the oil is the bigger factor as you need a minimum oil film thickness to withstand the bearing load. The wider the clearance, the more viscous the oil needs to be.
► 29.3 * 10^-9 * (.5 + .0043 * (1000 / 2.2)) * .002 * 2.2^2 * 9000 = 6.2655119999999999E-006
Stam
also remember that multiplication takes priority over addition, so multiply .0043*(1000/2.2) first, then at 0.5
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Re: Calculating journal bearing oiling requirements
The problem in terms of rod and main bearings is never having too much ( other then excess oil from too much rod side clearance) but not enough.
Without fail if some main bearing oil feed runs thru the block have a more turn filled path on the way to the main bearings, then why would you restrict those ?
Without fail if some main bearing oil feed runs thru the block have a more turn filled path on the way to the main bearings, then why would you restrict those ?
You can cut a man's tongue from his mouth, but that does not mean he’s a liar, it just shows that you fear the truth he might speak about you!
Re: Calculating journal bearing oiling requirements
The clearance factor is incorrect. It's not the clearance itself.Stan Weiss wrote: ↑Sun Jun 19, 2022 12:33 pmWhat have I done wrong?RDY4WAR wrote: ↑Sun Jun 19, 2022 11:47 am GPM = 29.3 x 10^-9(L + .0043(W/D))mD^2N
D = journal diameter (in inches)
L = bearing width (in inches)
m = bearing clearance factor
N = rotational speed
W = bearing load (in pounds)
This will get you your minimum. However, as has been stated, you can't really have too much. There's no benefit to restricting oil flow to a bearing. The viscosity of the oil is the bigger factor as you need a minimum oil film thickness to withstand the bearing load. The wider the clearance, the more viscous the oil needs to be.
► 29.3 * 10^-9 * (.5 + .0043 * (1000 / 2.2)) * .002 * 2.2^2 * 9000 = 6.2655119999999999E-006
Stam
Clearance factor = 1000(2C/D)
C = bearing clearance
D = journal diameter
There's an online calculator for this as well: https://calculator.academy/bearing-oil-flow-calculator/
Re: Calculating journal bearing oiling requirements
Sorry but I can't let this myth be stated without a rebuttal. This is false as "too much" side clearance does not influence oil flow volume past rod or main bearings. Bearing clearance regulates the flow.mag2555 wrote: ↑Sun Jun 19, 2022 2:06 pm The problem in terms of rod and main bearings is never having too much ( other then excess oil from too much rod side clearance) but not enough.
Without fail if some main bearing oil feed runs thru the block have a more turn filled path on the way to the main bearings, then why would you restrict those ?
Re: Calculating journal bearing oiling requirements
mag2555 wrote: ...... other then excess oil from too much rod side clearance ......
Unfortunately as an accurate statement it's pretty much discredited these days
This article outlines currently perceived wisdom on the subject
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Re: Calculating journal bearing oiling requirements
If you already have all the answers about this, then why are you asking this question ...?ELS wrote: ↑Sun Jun 19, 2022 11:53 amtoo much oil causes excessive friction (but not wear).Walter R. Malik wrote: ↑Sun Jun 19, 2022 10:47 amYou are never going to have to much oil going to a journal ... allow the bearing clearance to regulate the amount of flow.ELS wrote: ↑Sun Jun 19, 2022 9:27 am I want to calculate the ideal oil flow to a journal bearing, is there a formula or calculator that I can use?
also subquestion related to this; would it be a good idea to then install restriction jets to the oil pump side of the main bearing oiling holes? as to equalize oil flow to the main bearings?
and I'm not thinking of reducing oil flow to the mains, just to equalize them. the reason I'm asking for a formula to get the minimum required oil flow to a journal bearing is because in my engine design, if the oil pump drive shaft journals wear even a little bit, oil pressure suffers a lot, (dropping to around 0.4bar pressure at idle, around 2bar at redline)
this is because the supply to this journal bearing is straight from the oil filter and trough a 4mm hole as a restriction, then the oil needs to do a 90 degree turn to get to the main oil gallery
to fix this I will be tapping a carburetor fuel jet in this 4mm hole, but I want some guideline to what size of jet I will put in it, I don't want too little to cause premature wear, nor do I want too big which then defeats the purpose.
Probably because you are trying to find justification for what you think ...?
Sorry, I rained on your parade.
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Specialty engine building at its finest.
Re: Calculating journal bearing oiling requirements
what?Walter R. Malik wrote: ↑Sun Jun 19, 2022 4:51 pmIf you already have all the answers about this, then why are you asking this question ...?ELS wrote: ↑Sun Jun 19, 2022 11:53 amtoo much oil causes excessive friction (but not wear).Walter R. Malik wrote: ↑Sun Jun 19, 2022 10:47 am
You are never going to have to much oil going to a journal ... allow the bearing clearance to regulate the amount of flow.
and I'm not thinking of reducing oil flow to the mains, just to equalize them. the reason I'm asking for a formula to get the minimum required oil flow to a journal bearing is because in my engine design, if the oil pump drive shaft journals wear even a little bit, oil pressure suffers a lot, (dropping to around 0.4bar pressure at idle, around 2bar at redline)
this is because the supply to this journal bearing is straight from the oil filter and trough a 4mm hole as a restriction, then the oil needs to do a 90 degree turn to get to the main oil gallery
to fix this I will be tapping a carburetor fuel jet in this 4mm hole, but I want some guideline to what size of jet I will put in it, I don't want too little to cause premature wear, nor do I want too big which then defeats the purpose.
Probably because you are trying to find justification for what you think ...?
Sorry, I rained on your parade.
so because I ask, that means I know the answer already?
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Re: Calculating journal bearing oiling requirements
The old myth about connecting rod side clearance just will not die, or go away it seems.