We use cookies to provide you with a better experience. By continuing to browse the site you are agreeing to our use of cookies in accordance with our Privacy Policy.
A four-point contact ball bearing makes it easy to simplify
machine designs that combine radial, thrust and moment
loads, because it can handle all three simultaneously. They
are primarily used for slow-to-moderate-speed applications,
or where oscillatory movement is predominant.
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.
Bellows couplings first began to be
widely used by machine tool builders
in the mid-to-late 20th century. With the
advent of CNC technology, machine
engineers started looking to improve
upon some of the negative influences
traditional power transmission couplings
can have on a precision rotary /
linear motion system.
The use of motor current signature analysis (MCSA) for motor fault detection — such as
a broken rotor bar — is now well established. However, detection of mechanical faults
related to the driven system remains a more challenging task. Recently there has been a growing interest for detection of gear faults by MCSA. Advantages and drawbacks of these
MCSA-type techniques are presented and discussed on a few industrial cases.
Wear is a very important topic for dry running plastic gears. Over the past few years,
the authors have worked closely with a number of manufacturers of plastic gears
to investigate the problems of gear wear in detail. Together they have developed a calculation method that can be used to predict where and when local wear will occur on a tooth flank. Their findings have also just been published in the final version of VDI 2736.
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.
The changing landscape of hydraulic drives is leading many fluid power specialists to quickly adapt to using variable speed pump drives. Optimum utilization of these drives requires, in many cases, additional system design considerations.
EDITORS’ NOTE: “The Applications of Bevel Gears” is the excerpted third chapter of Dr. Hermann Stadtfeld’s latest book — Gleason Bevel Gear Technology (The Gleason Works,
Rochester, New York, USA; All rights reserved. 2014; ISBN 978-0-615-96492-8.), which appears here unabridged through the kind graces of Dr. Stadtfeld and Gleason Corp. Future installments will appear exclusively in Power Transmission Engineering
and Gear Technology magazine over the next 12 to
18 months.
Four types of gear devices with great transmission ratios (simply called great ratio gears or GRGs) are
discussed in this paper. They are strain wave gearing devices (SWGs), trochoidal gear reducers (TGRs),
hypocyclic gear reducers (HGRs) and James Ferguson-type planetary drives (JFDs). The structures, advantages and basic performances of these four devices are compared. The latest design and strength analysis methods are also introduced. To conclude, the future tendencies of GRGs are predicted.