# Bearing Calculator

Often, requests for rolling element bearing calculations appear here. I'd attached a simple bearing frequency calculator which may be useful.

You need to know the following information:

Ball/roller diameter

Bearing pitch diameter or bearing bore and outer diameter

The number of balls or rollers

The contact angle (use 0 if unknown)

The rotation rate.

Bearing dimensions may be inch or metric as long as the same units are used throughout.

The calculated frequencies are in the same units as the rotation rate. IF the roation rate is in Hz, the bearing tones are in Hz; if the rotation rate is entered as RPM, the calculated tones will be in CPM. Enter a rotation rate of 1 to calculate the results in orders.

No installation is needed. Just put the program file (BearingCalcs.exe) and the help file (help.pdf) in the same directory.

You may be familiar with my VibCon program for converting between various vibration units. You can find it on CTC's web site at www.ctconline.com. Bearing calculations may be incorporated into VibCon in the future.

I hope you find this a useful program.

Jon
Spintelligent Labs

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Original Post
Thank You very much Jon
Regards Lee
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Thanks Jon its really very handy program
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Jon,

Regards,
Rizal
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Jon i just used the program, good stuff.
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Hi All,
I just wanna give the simple way how to guess bearing defect frequencies (BPFO & BPFI) if you don't have complete data.
i.e.:
BPFI=0.6x(Number of ball or roll)xRunning Speed
BPFO=0.4x(Number of ball or roll)xRunning Speed
BSF=50%xBPFO
The unit of bearing defect depends on running speed unit.

Regards,

Rahardi
rahardi@gmail.com
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hi
hope that u all in good condition

the rule of thump for bearings freq.(for bearings with 8 to 12 ballz/rollers) says that BPO is uaually .4 times the number of balls, BPO is 0.6 times the number of balls, and Ft is 0.4 X.
defect of inner race (BPI)=0.6 n N
Defect of outer race (BPO)=0.4 nN
sefect on cage (FT) = 0.4 N

where N= speed in CPM
n= no.of balls

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Can someone shed some light on this bearing info I just received from Dodge?

Trying to figure out the fault frequencies on these. Or a way to calculate this into a number I can understand, so my bearing fault peak frequencies will line up on my software.

Is there a formula for this. I know there is a long detailed one which I have never used, but there must be an easier way.

Here is what they gave me, plus he uses RPS??

Here are the fault frequencies @ 1 RPS

8.645 outer ring
11.355 inner ring
3.584 roller
4322 cage

Thanks
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The inner and outer ring numbers have probably been given in orders. You can tell that because they add up to an exact integer, which will be the number of rolling elements (in this case 20.00)

I suspect the same is true for roller spin frequency, but you might check to see if that is reasonable for this bearing (what is the pn?).

Is there a decimal point missing on the cage frequency?
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Yea, thats what I'm sitting here trying to figure out. Cage number doesn't look right. Looks like orders on the rest like you say.

I need the # balls, pitch dia. etc to be able to use the bearing calclators posted in this group.

I'll have to contact the dodge rep back again to clear this up.
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Whats with the 1RPS, shouldn't that be converted to CPM or RPM?

quote:
Originally posted by Rockin' Rod:
Yea, thats what I'm sitting here trying to figure out. Cage number doesn't look right. Looks like orders on the rest like you say.

I need the # balls, pitch dia. etc to be able to use the bearing calclators posted in this group.

I'll have to contact the dodge rep back again to clear this up.
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I see what he's doing now. He's giving me the 1st fault freq line for each one. Here is the scan of the BPFO. Number matches but no peak there. Also the cage freq should have a decimal point in front of it.

.4322

quote:
Originally posted by Rockin' Rod:
Whats with the 1RPS, shouldn't that be converted to CPM or RPM?

quote:
Originally posted by Rockin' Rod:
Yea, thats what I'm sitting here trying to figure out. Cage number doesn't look right. Looks like orders on the rest like you say.

I need the # balls, pitch dia. etc to be able to use the bearing calclators posted in this group.

I'll have to contact the dodge rep back again to clear this up.

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Photos (1)
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Hi John,

I think a lot of people frequenting this board will be familiar with the formulae to calculate fault frequencies. Trouble is the input variables are usually unknown, unless the bearing number is available, in which case one can usually refer to databases that have the calculations done for you and also allow you to look at same bearing number versions with different number of rolling elements. The rotational speed is not required if you think in orders. Rgds.
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I've seen a couple of online calculators where all you do is input the bearing number and manufacturer, and it does the rest. I tried to download one yesterday but it would not open.

As far as knowing the specifics of each bearing, I had to request a book on those which I did receive. One being from NTN.

quote:
Originally posted by Vibe-Rater:
Hi John,

I think a lot of people frequenting this board will be familiar with the formulae to calculate fault frequencies. Trouble is the input variables are usually unknown, unless the bearing number is available, in which case one can usually refer to databases that have the calculations done for you and also allow you to look at same bearing number versions with different number of rolling elements. The rotational speed is not required if you think in orders. Rgds.
()

You can also check out an online bearing frequency calculator (amongst other tools) at:

It has over 2700 bearing numbers from different manufacturers and is easy to use.

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