Articles About ratings
(SPONSORED CONTENT)Understanding Your Gear Drive Ratings
The power capacity of a gear drive is important to ensure successful operation of driven equipment with minimum downtime. Making sure that the unit is correct for the application can be a difficult task. Download our whitepaper to achieve a better understanding of your gear drive ratings. White Papers Courtesy of Rexnord
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When comparing bearing suppliers, engineers are often left with few options other than to compare dynamic load ratings and corresponding life calculations. Of course, we can look at steel and manufacturing quality; but if we are comparing sources of similar quality, those items may not provide a large contrast. It often surprises people to learn that bearing capacities are calculated values, not tested values. Lately, however, a trend is emerging for bearing suppliers to increase their ratings for higher performance bearings that have premium features such as higher quality steel and specilaized heat treatment. Bearing companies are under intense competitive pressure to make every feature add to the dynamic capacity of their bearings because it is very well understood that an increase in capacity adds to the bottom line.
"Well begun is half done," a quote that most reference materials attribute to Aristotle, certainly applies when selecting mechanical power transmission products. A selection process that is well thought out at the start can ensure that the product selected will be properly sized and appropriate to the application at hand.
Power Transmission Engineering is collaborating with the Bearing Specialists Association (BSA) on a special section within the magazine. Bearing Briefs will present updated reports on bearing topics for each issue in 2016. Complimentary access to all BSA Bearing and Industry Briefs is available on the BSA website at www.bsahome.org/tools.
This issue our Baldor Basics series continues with the topics of motor temperature ratings and metric motors.
In 1991, Needelman and Zaretsky presented a set of empirically derived equations for bearing fatigue life (adjustment) factors (LFs) as a function of oil filter ratings.
American Bearing Manufacturers Association (ABMA) Standard 9 and ISO 281 give equations for calculating the basic dynamic radial load rating for ball bearings. These equations are based on a number of assumptions, many of which are not valid for thin-section bearings. (Thin-section bearings are described in ABMA standard 26.2.) Nevertheless, many thin-section bearing catalogs report load ratings based on these equations. Kaydon has developed a new method for calculating the dynamic radial load rating for thin-section ball bearings. The new method uses the contact stress and the number of stress-cycles-per-revolution to calculate the capacity. The new numbers are based on five years of actual test results. These equations can also be used to calculate the dynamic radial load rating for four-point contact ball bearings, which are not covered in ABMA standard 9 or ISO 281.
Engineers typically learn that the bearing L10 life can be estimated using the so called “C/P method” — or the “basic rating life” of the bearing, a method rooted in the 1940s. Major developments have since led to the “modified rating life,” released in ISO 281:2007, which includes the aiso life modification factor. In this paper a succession of equations used for bearing life ratings are reviewed, and current bearing life rating practices are discussed in detail. It is shown that — despite the introduction more than 30 years ago of the adjustment factor of the basic rating life, and the standardization in 2007 of the aiso modification factor — use of these improved calculation methods are not practiced by all engineers. Indeed — many continue referring to the old model as a way of seeking compliance with existing, established practices.
News Items About ratings
1 Bison Gears Hollow Shaft Gearmotor Doubles Continuous Torque Ratings (March 10, 2006)
Bison Gears new 562 series hollow shaft gearmotor offers increased low speed center distance coupled with greater clearance for wid...