Bearing Friction

Ever wondered about bearing friction, or perhaps wanted to design something but not sure what type of bearing you should use to prevent premature failure do to to much friction keeping bearing from performing as designed.  Well below you fill find some useful information to better help you understand how different type of applications and bearing combinations work with friction created by moving parts to help you choose the right type of bearing for your application.  This also gives you a brief intro to how different lubrication methods help with friction.


Torque required to put a bearing into motion from rest is usually higher than that required to keep the bearing running once it starts. Starting friction, therefore, has an important influence on the power required in a bearing drive system.
Externally pressurized bearings have very low starting torque. Roller bearings have a low starting torque and underpressurized sleeve (fluid-film) bearings have substantially higher starting torque. The coefficient of friction at start-up for self-lubricated bearings is highly variable. It may range from 0.04 to 0.16.
The fluid-film bearing has a high starting torque because it passes through boundary lubrication stages as it comes up to speed. Once running under a hydrodynamic film, the fluid-film bearing exhibits friction characteristics comparable to a rolling-element bearing.
At running speed, the externally pressurized bearing runs with low friction. Friction in a self-lubricating sleeve bearing is quite variable depending upon the application.
Running friction for a rolling-element bearing is lower than its starting friction. If torque characteristics are critical to a bearing design, starting and running frictional characteristics should be measured experimentally.
When a bearing must be started repeatedly under heavy load, rolling-element bearings offer a better choice than sleeve bearings. When the increased complexity is acceptable, an externally pressurized (hydrostatic) bearing is the best choice. When starting load is light and load increases gradually with speed, the conventional hydrodynamic sleeve bearing usually is preferred.
The frictional properties of any plain bearing depend on the lubrication system. Either hydrodynamic or hydrostatic lubrication can provide low friction. A gas bearing offers the lowest friction levels.
Friction in hydrodynamic and hydrostatic bearings is a function of lubricant viscosity and shear rate. Shear rate increases with increasing rotational speed and decreasing film thickness. Friction coefficient is generally below 0.001.
Self-lubricated bearings vary widely. It is difficult to predict performance for a given bearing / lubricant system. The range of coefficients of friction is 0.01 to 0.10 for boundary lubrication and 0.01 to 0.3 for self-lubrication.
Caution must be used when applying friction coefficient handbook data. Conditions under which the values were measured should be known and duplicated in the application. Coefficient of friction tends to increase with increasing surface roughness, dryness, and cleanliness of surfaces, and decreasing temperature.

Help Japan Before time Runs out!!!

Well here we are at the end of March and as promised would donate half of our profits to the recovery efforts in Japan. Hurry and help the cause before its to late as today is the last day of the event "buy a bearing for Japans Recovery"  For more information about whats going on with Lonestar Bearings Follow us here or find us on Twitter and Facebook.

Tapered Bearings Going for Cheap while they last.

Check out this spring Blowout on lm11949 tapered bearings!!! 95 cents a piece get them while they last!! With prices this cheap they arent going to be available long so act now! We also have many more tapered bearings radial bearings and disc harrow bearings  available for purchase on our website Lonestar Bearings or contact us by phone or email for any questions you may have.

Common Bearing Failures

Common Bearing FailuresEver wondered what the root cause of your bearing failing is.  Well often times its not just because its old.  There are many things to look for when finding a failing bearing and replacing it that may potentially help you eliminate more down time and costly repairs.  Many times we are upset that we have to shut down to replace a bearing and in a h...aste to get our piece of machinery back together and producing for us, that we sometimes end up causing more down time by failing to examine failed bearing to get answers to reason its failed to correct those issues and prevent another premature failure.  Below I have  broken down each reason for premature failure and given you the common tell tale signs you will see on the failed bearing you pull to replace.

Excessive Load

Tight fits,brinelling and improper
preloading can bring about
early failure.
The solution is to reduce the
load or redesign using a bearing
with greater capacity.

Overheating

Symptoms include discoloration of the metal from
silver or gold to  a blue or purple color around ball or rings.
Temperatures in excess of 400 degrees F can cause brittle metal
allowing for stress cracks/pitting and deformation in severe cases.
Excessive heat will degrade/destroy lubricants.

Brinelling(Pitting)

Commonly called pitting. this occurs when the load
surpasses the elastic capabilities of the ring material
The visual indication of this is indentations in the race
This increases bearing noise and creates vibrations which
causes unnormal wear and premature bearing failure

These are just a few common symptoms of premature bearing failure.


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