# Questions on bearings and loads

Hope the group collective can help.
If a bearings dynamic load is 14.8 KN and static load is 7.8 KN. Am I
correct in working out that statically the bearing will take a weight of
7.8 x 1000 /9.8 = 796 kg.
And dynamically it would be approx equivalent to 1.5 metric tonne.
I know that Newton is a measure of force, mass x acceleration but using
gravity in this to give me an idea of the forces involved.
Please let me know if this makes sense or if I am wrong.
What sort of bearings are we talking about here? For ball and roller bearings, the static load is that which causes a specific amount of plastic deformation (one ten thousandth of the bore diameter, if I recall correctly). The dynamic capacity is the load which will cause 10% of bearings to fail by fatigue pitting in one million or perhaps three million revolutions (depending on the manufacturer). In the old old days I thing it was RHP bearings who did their sums on 300 million revs, which made their performance look very inferior to SKF, where the calc was based on one million. The point is, the "capacities" are based on some performance criterion.
Your force convertions are OK, I think.
You are right. On this planet.
Nick
SKF deep grove single ball race with 25 mm internal bore 62 mm external dia.
If the calcs are OK then, it will do, Max rpm will likely be around 300 rpm max and static loads around 150 kg for two bearings.
Thanks
Sorry that should be 52 mm external dia.
Assuming 150 kg per bearing your "L10" life (ten percent probability of fatigue) will be about 20 years continuous operation. This assumes it doesn't overheat and cook the grease or that it doesn't fill up with grit or water.
That will certainly be longer then the predicted life of the kart.
Grit and water are the expected killers, so must keep pumping through the grease.
On or around Wed, 04 Apr 2007 15:51:06 -0500, Adrian Hodgson enlightened us thusly:
I think that sounds right. static load is less than dynamic.
beware of shock loading if the application is subject to such things.

#### Site Timeline

• Below is a link to a photo of the end of my turret mill, can anyone identify the...
• next in

## ⚙ Model Engineering in the UK

• Just thought I would follow up my question a few weeks ago about DROs, and let...
• previous in

## ⚙ Model Engineering in the UK

• The UK Government is proposing to limit the concentration of acids and some...
• last updated in

## ⚙ Model Engineering in the UK

• The UK Government is proposing to limit the concentration of acids and some...
• last posted in

## ⚙ Model Engineering in the UK

• >> >>>> Yesterday I found myself cleaning up a bit of square tube in >>>>...
• site's last updated in

## ⏣ General Metalworking

• Grawitacja pomaga wytwarzać światło, a to tylko początek niezwykłych...