Ball bearing

Bearing (mechanical)From Wikipedia, the free encyclopedia

A bearing is a machine element that constrains relative motionbetween moving parts to only the desired motion. The design of thebearing may, for example, provide for free linear movement of themoving part or for free rotation around a fixed axis; or, it mayprevent a motion by controlling the vectors of normal forces that bearon the moving parts. Many bearings also facilitate the desired motionas much as possible, such as by minimizing friction. Bearings areclassified broadly according to the type of operation, the motionsallowed, or to the directions of the loads (forces) applied to the parts.

The term "bearing" is derived from the verb "to bear";[1] a bearingbeing a machine element that allows one part to bear (i.e., to support)another. The simplest bearings are bearing surfaces, cut or formedinto a part, with varying degrees of control over the form, size,roughness and location of the surface. Other bearings are separatedevices installed into a machine or machine part. The mostsophisticated bearings for the most demanding applications are very precise devices; their manufacture requiressome of the highest standards of current technology.

Contents

1 History

2 Common

3 Principles of operation

4 Motions

5 Friction6 Loads

7 Speeds

8 Play

9 Stiffness

10 Service life

10.1 L10 life

10.2 External factors

11 Maintenance and lubrication11.1 Rolling Element Bearing Outer Race Fault Detection

11.2 Packing

11.3 Ring oiler

11.4 Splash lubrication

11.5 Pressure lubrication

12 Types

13 See also

14 References

15 External links

Tapered roller bearing

Drawing of Leonardo da Vinci (1452-

1519) Study of a ball bearing

History

The invention of the rolling bearing, in the form of wooden rollers supporting,or bearing, an object being moved is of great antiquity, and may predate theinvention of the wheel.

Though it is often claimed that the Egyptians used roller bearings in the form

of tree trunks under sleds,[2] this is modern speculation.[3] They are depicted

in their own drawings in the tomb of Djehutihotep [4] as moving massive stoneblocks on sledges with the runners lubricated with a liquid which wouldconstitute a plain bearing. There are also Egyptian drawings of

bearings used with hand drills.[5]

The earliest recovered example of a rolling element bearing is awooden ball bearing supporting a rotating table from the remains ofthe Roman Nemi ships in Lake Nemi, Italy. The wrecks were dated

to 40 AD.[6][7]

Leonardo da Vinci incorporated drawings of ball bearings in hisdesign for a helicopter around the year 1500. This is the first recordeduse of bearings in an aerospace design. However, Agostino Ramelli is

the first to have published sketches of roller and thrust bearings.[2] Anissue with ball and roller bearings is that the balls or rollers rub againsteach other causing additional friction which can be prevented byenclosing the balls or rollers in a cage. The captured, or caged, ball bearing was originally described by Galileo

in the 17th century.[citation needed] The mounting of bearings into a set was not accomplished for many yearsafter that. The first patent for a ball race was by Philip Vaughan of Carmarthen in 1794.

Bearings saw use for holding wheel and axles. The bearings used there were plain bearings that were used togreatly reduce friction over that of dragging an object by making the friction act over a shorter distance as thewheel turned.

The first plain and rolling-element bearings were wood closely followed by bronze. Over their history bearingshave been made of many materials including ceramic, sapphire, glass, steel, bronze, other metals and plastic(e.g., nylon, polyoxymethylene, polytetrafluoroethylene, and UHMWPE) which are all used today.

Watch makers produce "jeweled" watches using sapphire plain bearings to reduce friction thus allowing moreprecise time keeping.

Even basic materials can have good durability. As examples, wooden bearings can still be seen today in oldclocks or in water mills where the water provides cooling and lubrication.

The first practical caged-roller bearing was invented in the mid-1740s by horologist John Harrison for his H3marine timekeeper. This uses the bearing for a very limited oscillating motion but Harrison also used a similarbearing in a truly rotary application in a contemporaneous regulator clock.

A patent on ball bearings, reportedly the first, was awarded to Jules Suriray, a Parisian bicycle mechanic, on 3August 1869. The bearings were then fitted to the winning bicycle ridden by James Moore in the world's first

bicycle road race, Paris-Rouen, in November 1869.[8]

Early Timken tapered roller bearing

with notched rollers

In 1883, Friedrich Fischer, founder of FAG, developed an approach for milling and grinding balls of equal sizeand exact roundness by means of a suitable production machine and formed the foundation for creation of anindependent bearing industry.

The modern, self-aligning design of ball bearing is attributed to Sven Wingquist of the SKF ball-bearingmanufacturer in 1907, when he was awarded Swedish patent No.25406 on its design.

Henry Timken, a 19th-century visionary and innovator in carriagemanufacturing, patented the tapered roller bearing in 1898. Thefollowing year he formed a company to produce his innovation. Overa century the company grew to make bearings of all types, includingspecialty steel and an array of related products and services.

Erich Franke invented and patented the wire race bearing in 1934.His focus was on a bearing design with a cross section as small aspossible and which could be integrated into the enclosing design.After World War II he founded together with Gerhard Heydrich thecompany Franke & Heydrich KG (today Franke GmbH) to push thedevelopment and production of wire race bearings.

Richard Stribecks extensive research [9][10] on ball bearing steels

identified the metallurgy of the commonly used 100Cr6 (AISI 52100) [11] showing coefficient of friction as afunction of pressure.

Designed in 1968 and later patented in 1972, Bishop-Wisecarver's co-founder Bud Wisecarver created veegroove bearing guide wheels, a type of linear motion bearing consisting of both an external and internal 90-

degree vee angle.[12]

In the early 1980s, Pacific Bearing's founder, Robert Schroeder, invented the first bi-material plain bearingwhich was size interchangeable with linear ball bearings. This bearing had a metal shell (aluminum, steel or

stainless steel) and a layer of Teflon-based material connected by a thin adhesive layer.[13]

Today ball and roller bearings are used in many applications which include a rotating component. Examplesinclude ultra high speed bearings in dental drills, aerospace bearings in the Mars Rover, gearbox and wheelbearings on automobiles, flexure bearings in optical alignment systems and bicycle wheel hubs.

Common

By far, the most common bearing is the plain bearing, a bearing which uses surfaces in rubbing contact, oftenwith a lubricant such as oil or graphite. A plain bearing may or may not be a discrete device. It may be nothingmore than the bearing surface of a hole with a shaft passing through it, or of a planar surface that bears another(in these cases, not a discrete device); or it may be a layer of bearing metal either fused to the substrate (semi-discrete) or in the form of a separable sleeve (discrete). With suitable lubrication, plain bearings often giveentirely acceptable accuracy, life, and friction at minimal cost. Therefore, they are very widely used.

However, there are many applications where a more suitable bearing can improve efficiency, accuracy, serviceintervals, reliability, speed of operation, size, weight, and costs of purchasing and operating machinery.

Thus, there are many types of bearings, with varying shape, material, lubrication, principle of operation, and soon.

Animation of ball bearing (without a

cage). The inner ring rotates and the

outer ring is standstill.

Principles of operation

There are at least 6 common principles of operation:

plain bearing, also known by the specific styles: bushing,

journal bearing, sleeve bearing, rifle bearingrolling-element bearing such as ball bearings and roller bearings

jewel bearing, in which the load is carried by rolling the axle

slightly off-center

fluid bearing, in which the load is carried by a gas or liquidmagnetic bearing, in which the load is carried by a magnetic

field

flexure bearing, in which the motion is supported by a load

element which bends.

Motions

Common motions permitted by bearings are:

axial rotation e.g. shaft rotation

linear motion e.g. drawerspherical rotation e.g. ball and socket joint

hinge motion e.g. door, elbow, knee

Friction

Reducing friction in bearings is often important for efficiency, to reduce wear and to facilitate extended use athigh speeds and to avoid overheating and premature failure of the bearing. Essentially, a bearing can reducefriction by virtue of its shape, by its material, or by introducing and containing a fluid between surfaces or byseparating the surfaces with an electromagnetic field.

By shape, gains advantage usually by using spheres or rollers, or by forming flexure bearings.

By material, exploits the nature of the bearing material used. (An example would be using plastics that

have low surface friction.)By fluid, exploits the low viscosity of a layer of fluid, such as a lubricant or as a pressurized medium to

keep the two solid parts from touching, or by reducing the normal force between them.

By fields, exploits electromagnetic fields, such as magnetic fields, to keep solid parts from touching.

Combinations of these can even be employed within the same bearing. An example of this is where the cage ismade of plastic, and it separates the rollers/balls, which reduce friction by their shape and finish.

Loads

Bearings vary greatly over the size and directions of forces that they can support.

Forces can be predominately radial, axial (thrust bearings) or bending moments perpendicular to the main axis.

Speeds

Different bearing types have different operating speed limits. Speed is typically specified as maximum relativesurface speeds, often specified ft/s or m/s. Rotational bearings typically describe performance in terms of theproduct DN where D is the mean diameter (often in mm) of the bearing and N is the rotation rate in revolutionsper minute.

Generally there is considerable speed range overlap between bearing types. Plain bearings typically handle onlylower speeds, rolling element bearings are faster, followed by fluid bearings and finally magnetic bearings whichare limited ultimately by centripetal force overcoming material strength.

Play

Some applications apply bearing loads from varying directions and accept only limited play or "slop" as theapplied load changes. One source of motion is gaps or "play" in the bearing. For example, a 10 mm shaft in a12 mm hole has 2 mm play.

Allowable play varies greatly depending on the use. As example, a wheelbarrow wheel supports radial and axialloads. Axial loads may be hundreds of newtons force left or right, and it is typically acceptable for the wheel towobble by as much as 10 mm under the varying load. In contrast, a lathe may position a cutting tool to0.02 mm using a ball lead screw held by rotating bearings. The bearings support axial loads of thousands ofnewtons in either direction, and must hold the ball lead screw to 0.002 mm across that range of loads.

Stiffness

A second source of motion is elasticity in the bearing itself. For example, the balls in a ball bearing are like stiffrubber, and under load deform from round to a slightly flattened shape. The race is also elastic and develops aslight dent where the ball presses on it.

The stiffness of a bearing is how the distance between the parts which are separated by the bearing varies withapplied load. With rolling element bearings this is due to the strain of the ball and race. With fluid bearings it isdue to how the pressure of the fluid varies with the gap (when correctly loaded, fluid bearings are typically stifferthan rolling element bearings).

Service life

Fluid and magnetic bearings

Main articles: Fluid bearing and Magnetic bearing

Fluid and magnetic bearings can have practically indefinite service lives. In practice, there are fluid bearingssupporting high loads in hydroelectric plants that have been in nearly continuous service since about 1900 andwhich show no signs of wear.

Rolling element bearings

Rolling element bearing life is determined by load, temperature, maintenance, lubrication, material defects,contamination, handling, installation and other factors. These factors can all have a significant effect on bearinglife. For example, the service life of bearings in one application was extended dramatically by changing how thebearings were stored before installation and use, as vibrations during storage caused lubricant failure even when

the only load on the bearing was its own weight;[14] the resulting damage is often false brinelling. Bearing life is

statistical: several samples of a given bearing will often exhibit a bell curve of service life, with a few samplesshowing significantly better or worse life. Bearing life varies because microscopic structure and contaminationvary greatly even where macroscopically they seem identical.

L10 life

Bearings are often specified to give an "L10" life (outside the USA, it may be referred to as "B10" life.) This isthe life at which ten percent of the bearings in that application can be expected to have failed due to classicalfatigue failure (and not any other mode of failure like lubrication starvation, wrong mounting etc.), or,alternatively, the life at which ninety percent will still be operating.The L10 life of the bearing is theoretical lifeand may not represent service life of the bearing. Bearings are also rated using C0 (static loading) value. This is

the basic load rating as a reference, and not an actual load value.

Plain bearings

For plain bearings some materials give much longer life than others. Some of the John Harrison clocks stilloperate after hundreds of years because of the lignum vitae wood employed in their construction, whereas hismetal clocks are seldom run due to potential wear.

Flexure bearings

Flexure bearings rely on elastic properties of material.Flexure bearings bend a piece of material repeatedly.Some materials fail after repeated bending, even at low loads, but careful material selection and bearing designcan make flexure bearing life indefinite.

Short-life bearings

Although long bearing life is often desirable, it is sometimes not necessary. Harris describes a bearing for arocket motor oxygen pump that gave several hours life, far in excess of the several tens of minutes life

needed.[14]

External factors

The service life of the bearing is affected by many parameters that are not controlled by the bearingmanufactures. For example, bearing mounting, temperature, exposure to external environment, lubricantcleanliness and electrical currents through bearings etc.

Maintenance and lubrication

Many bearings require periodic maintenance to prevent premature failure, but many others require littlemaintenance. The latter include various kinds of fluid and magnetic bearings, as well as rolling-element bearingsthat are described with terms including sealed bearing and sealed for life. These contain seals to keep the dirtout and the grease in. They work successfully in many applications, providing maintenance-free operation. Someapplications cannot use them effectively.

Nonsealed bearings often have a grease fitting, for periodic lubrication with a grease gun, or an oil cup forperiodic filling with oil. Before the 1970s, sealed bearings were not encountered on most machinery, and oilingand greasing were a more common activity than they are today. For example, automotive chassis used torequire "lube jobs" nearly as often as engine oil changes, but today's car chassis are mostly sealed for life. Fromthe late 1700s through mid 1900s, industry relied on many workers called oilers to lubricate machineryfrequently with oil cans.

Factory machines today usually have lube systems, in which a central pump serves periodic charges of oil orgrease from a reservoir through lube lines to the various lube points in the machine's bearing surfaces, bearingjournals, pillow blocks, and so on. The timing and number of such lube cycles is controlled by the machine'scomputerized control, such as PLC or CNC, as well as by manual override functions when occasionallyneeded. This automated process is how all modern CNC machine tools and many other modern factorymachines are lubricated. Similar lube systems are also used on nonautomated machines, in which case there is ahand pump that a machine operator is supposed to pump once daily (for machines in constant use) or onceweekly. These are called one-shot systems from their chief selling point: one pull on one handle to lube thewhole machine, instead of a dozen pumps of an alemite gun or oil can in a dozen different positions around themachine.

The oiling system inside a modern automotive or truck engine is similar in concept to the lube systems mentionedabove, except that oil is pumped continuously. Much of this oil flows through passages drilled or cast into theengine block and cylinder heads, escaping through ports directly onto bearings, and squirting elsewhere toprovide an oil bath. The oil pump simply pumps constantly, and any excess pumped oil continuously escapesthrough a relief valve back into the sump.

Many bearings in high-cycle industrial operations need periodic lubrication and cleaning, and many requireoccasional adjustment, such as pre-load adjustment, to minimise the effects of wear.

Bearing life is often much better when the bearing is kept clean and well lubricated. However, many applicationsmake good maintenance difficult. For example, bearings in the conveyor of a rock crusher are exposedcontinually to hard abrasive particles. Cleaning is of little use, because cleaning is expensive yet the bearing iscontaminated again as soon as the conveyor resumes operation. Thus, a good maintenance program mightlubricate the bearings frequently but not include any disassembly for cleaning. The frequent lubrication, by itsnature, provides a limited kind of cleaning action, by displacing older (grit-filled) oil or grease with a freshcharge, which itself collects grit before being displaced by the next cycle.

Rolling Element Bearing Outer Race Fault Detection

The Rolling Element Bearing is widely used in the Industries today and hence maintenance of these bearingsbecomes an important task for the maintenance professionals. The Rolling Element bearings wear out easily dueto metal to metal contact which creates faults in the outer race, inner race and ball. It is also however the mostvulnerable component of a machine because it is often under high load and high running speed conditions.Regular diagnostics of rolling element bearing faults is critical for industrial safety and operations of the machinesalong with reducing the maintenance costs or avoiding shutdown time. Among the outer race, inner race andball, the outer race tends to be more vulnerable to faults and defects.

There is still a room for discussion if the rolling element excites the natural frequencies of bearing componentwhen it passes the fault on the outer race. Hence we need to identify the bearing outer race natural frequencyand its harmonics. The bearing faults create impulses and results in strong harmonics of the fault frequencies inthe spectrum of vibration signals. These fault frequencies are sometimes masked by adjacent frequencies in thespectra due to their little energy. Hence, a very high spectral resolution is often needed to identify thesefrequencies during a FFT analysis. The natural frequencies of a rolling element bearing with the free boundaryconditions are 3kHz. Therefore, in order to use the bearing component resonance bandwidth method to detectthe bearing fault at an initial stage a high frequency range accelerometer should be adopted and data obtainedfrom a long duration needs to be acquired. A fault characteristic frequency can only be identified when the faultextent is severe, such as that of a presence of a hole in the outer race. The harmonics of fault frequency is amore sensitive indicator of a bearing outer race fault. For a more serious detection of defected bearing faultswaveform, spectrum and envelope techniques will help reveal these faults. However, if a high frequency

demodulation is used in the envelope analysis in order to detect bearing fault characteristic frequencies themaintenance professionals have to be more careful in the analysis because of resonance, as it may or may notcontain fault frequency components.

Using spectral analysis as a tool to identify the faults in the bearings face challenges due to issues like lowenergy, signal smearing, cyclostationarity etc.,. High resolution is often desired to differentiate the fault frequencycomponents from the other high amplitude adjacent frequencies.Hence, when the signal is sampled for FFTanalysis, the sample length should be large enough to give adequate frequency resolution in the spectrum. Also,keeping the computation time and memory within limits and avoiding unwanted aliasing may be demanding.However, a minimum frequency resolution required can be obtained by estimating the bearing fault frequenciesand other vibration frequency components and its harmonics due to shaft speed, misalignment, line frequency,gearbox etc.

Packing

Some bearings use a thick grease for lubrication, which is pushed into the gaps between the bearing surfaces,also known as packing. The grease is held in place by a plastic, leather, or rubber gasket (also called a gland)that covers the inside and outside edges of the bearing race to keep the grease from escaping.

Bearings may also be packed with other materials. Historically, the wheels on railroad cars used sleeve bearings

packed with waste or loose scraps cotton or wool fiber soaked in oil, then later used solid pads of cotton.[15]

Ring oiler

For more details on this topic, see Ring oiler.

Bearings can be lubricated by a metal ring that rides loosely on the central rotating shaft of the bearing. The ringhangs down into a chamber containing lubricating oil. As the bearing rotates, viscous adhesion draws oil up thering and onto the shaft, where the oil migrates into the bearing to lubricate it. Excess oil is flung off and collects in

the pool again.[16]

Splash lubrication

Some machines contain a pool of lubricant in the bottom, with gears partially immersed in the liquid, or crankrods that can swing down into the pool as the device operates. The spinning wheels fling oil into the air aroundthem, while the crank rods slap at the surface of the oil, splashing it randomly on the interior surfaces of theengine. Some small internal combustion engines specifically contain special plastic flinger wheels which

randomly scatter oil around the interior of the mechanism.[17]

Pressure lubrication

For high speed and high power machines, a loss of lubricant can result in rapid bearing heating and damage dueto friction. Also in dirty environments the oil can become contaminated with dust or debris that increases friction.In these applications, a fresh supply of lubricant can be continuously supplied to the bearing and all other contactsurfaces, and the excess can be collected for filtration, cooling, and possibly reuse. Pressure oiling is commonlyused in large and complex internal combustion engines in parts of the engine where directly splashed oil cannot

reach, such as up into overhead valve assemblies.[18] High speed turbochargers also typically require apressurized oil system to cool the bearings and keep them from burning up due to the heat from the turbine.

Types

There are many different types of bearings.

Type Description Friction Stiffness Speed Life Notes

Plain

bearing

Rubbing

surfaces,

usually withlubricant; some

bearings use

pumped

lubrication and

behave similarly

to fluid

bearings.

Depends on materialsand construction,

PTFE has coefficient

of friction ~0.05-0.35,

depending upon fillers

added

Good,

providedwear is

low, but

some

slack is

normally

present

Low to

very high

Low to very high

- depends upon

application and

lubrication

Widely used,relatively high

friction, suffers

from stiction in

some

applications.

Depending upon

the application,lifetime can be

higher or lower

than rolling

element

bearings.

Rolling

element

bearing

Ball or rollers

are used to

prevent or

minimise

rubbing

Rolling coefficient offriction with steel can

be ~0.005 (adding

resistance due to

seals, packed grease,

preload and

misalignment can

increase friction to asmuch as 0.125)

Good, but

some

slack is

usually

present

Moderate

to high

(often

requires

cooling)

Moderate to

high (depends on

lubrication, often

requires

maintenance)

Used for higher

moment loads

than plain

bearings with

lower friction

Jewel

bearing

Off-center

bearing rolls inseating

LowLow due

to flexingLow

Adequate

(requiresmaintenance)

Mainly used in

low-load, high

precision work

such as clocks.Jewel bearings

may be very

small.

Fluid

bearing

Fluid is forcedbetween two

faces and held

in by edge seal

Zero friction at zero

speed, lowVery high

Very high

(usually

limited to

a few

hundred

feet per

secondat/by

seal)

Virtually infinite

in some

applications,may wear at

startup/shutdown

in some cases.

Often negligible

maintenance.

Can fail quickly

due to grit ordust or other

contaminants.

Maintenance

free in

continuous use.

Can handle very

large loads withlow friction.

Faces ofbearing are

kept separate

Zero friction at zero

speed, but constantpower for levitation,

eddy currents are NoIndefinite.

Active magnetic

bearings (AMB)need

considerable

Magnetic

bearings

by magnets

(electromagnets

or eddy

currents)

often induced when

movement occurs, but

may be negligible if

magnetic field is quasi-

static

Low practical

limit

Maintenance

free. (with

electromagnets)

power.

Electrodynamic

bearings (EDB)

do not require

external power.

Flexure

bearing

Material flexesto give and

constrain

movement

Very low LowVery

high.

Very high or low

depending on

materials andstrain in

application.

Usually

maintenance

free.

Limited range of

movement, no

backlash,

extremely

smooth motion

Stiffness is the amount that the gap varies when the load on the bearing changes, it is distinct from the friction

of the bearing.

See also

Ball bearing

Ball spline

Hertz contact stressHinge

Main bearing

Needle roller bearing

Pillow block bearing

Race (bearing)Rolamite

Scrollerwheel

Shock Pulse Method

Slewing bearing

Spherical bearingSpiral groove bearing

References

1. ^ Merriam-Webster, "headwords "bearing" and "bear"" (http://unabridged.merriam-webster.com/collegiate.htm), Merriam-Webster's Collegiate Dictionary, online subscription version. Paywalledreference work.

2. ^a b American Society of Mechanical Engineers (1906), Transactions of the American Society of Mechanical

Engineers (http://books.google.com/books?id=aWd1G50m8WEC&pg=RA1-PA441) 27, American Society ofMechanical Engineers, p. 441.

3. ^ Bryan Bunch, The history of science and technology.

4. ^ Steven Blake Shubert, Encyclopedia of the archaeology of ancient Egypt

5. ^ Guran, Ardshir; Rand, Richard H. (1997), Nonlinear dynamics (http://books.google.com/books?id=ttBQ1k8MYZ4C&pg=PA178&lpg=PA178), World Scientific, p. 178, ISBN 978-981-02-2982-5.

6. ^ Purtell, John (1999/2001). Project Diana, chapter 10: http://nemiship.multiservers.com/nemi.htm

7. ^ Bearing Industry Timeline (http://www.americanbearings.org/?page=bearing_timeline), retrieved 2012-10-21.

8. ^ "Bicycle History, Chronology of the Growth of Bicycling and the Development of Bicycle Technology byDavid Mozer" (http://www.ibike.org/library/history-timeline.htm). Ibike.org. Retrieved 2013-09-30.

9. ^ R. Stribeck, Kugellager fr beliebige Belastungen Zeitschrift des Vereins Deutscher Ingenieure, 1901, Nr. 3,Band 45, p. 73-79

10. ^ N.N. (R. Stribeck), Kugellager (ball bearings), Glasers Annalen fr Gewerbe und Bauwesen, 1901, No. 577,p. 2-9, Published 01. July 1901

11. ^ A. Martens, Schmierluntersuchungen (Investigations on oils) Part I: Mitteilungen aus den Kniglichentechnischen Versuchsanstalten zu Berlin, Ergnzungsheft III 1888, p. 1-37, Verlag von Julius Springer, Berlinand Part II: Mitteilungen aus den Kniglichen technischen Versuchsanstalten zu Berlin, Ergnzungsheft V, 1889,

p. 1-57, Verlag von Julius Springer, Berlin, (Note: These files can be downloaded from the website of BAM:http://www.bam.de/de/ueber_uns/geschichte/adolf_martens.htm)

12. ^ Machine Design (2007), Did You Know: Bud Wisecarver(http://www.bwc.com/pdf/news/1737_MSD_BIWI_eprint_.pdf), Machine Design, p. 1.

13. ^ "Design News Magazine - July 1995" (http://www.designnews.com/article/9409-Prime_mover_in_custom_bearings.php).

14. ^a b Harris, Tedric A. (2000, 4th edition). Rolling Bearing Analysis. Wiley-Interscience. ISBN 0-471-35457-0.

15. ^ White, John H. (1985) [1978]. The American Railroad Passenger Car (http://books.google.com/books?

id=RAidPrpZUNQC) 2. Baltimore, MD: Johns Hopkins University Press. p. 518. ISBN 0801827477.OCLC 11469984 (//www.worldcat.org/oclc/11469984).

16. ^ Steam Power Plant Engineering, by George Frederick Gebhardt, published by J. Wiley & sons, Incorporated,1917, p 791 Google Books scanned ref (http://books.google.com/books?id=6QhMAAAAMAAJ&dq=ring%20oiler&pg=PA791#v=onepage&q=ring%20oiler&f=false)

17. ^ The gasoline automobile, George William Hobbs b. 1887, Ben George Elliott, Earl Lester Consoliver,University of Wisconsin. University Extension Division, McGraw-Hill Book Company, Inc., 1919 - 483 pages,pp 111-114 Google Books scanned ref (http://books.google.com/books?id=kWJVAAAAMAAJ&pg=PA114&dq=splash+lubrication&hl=en&sa=X&ei=qN1zT8qZCcbl0gG77uT_Ag&ved=0CFAQ6AEwBA#v=onepage&q=splash%20lubrication&f=false)

18. ^ Pressure Lubricating Characteristics, by Paul Dumas, Motor age, Volume 42, Class Journal Co., 14 Sep 1922Google Books scanned ref (http://books.google.com/books?id=S0AfAQAAMAAJ&pg=RA10-PA22&dq=engine+pressure+oiling&hl=en&sa=X&ei=hZlzT-P5L6bt0gGhstH_Ag&ved=0CEUQ6AEwAA#v=onepage&q=engine%20pressure%20oiling&f=false)

External links

Comprehensive review on bearings, University of Cambridge (http://www.msm.cam.ac.uk/phase-trans/2011/Bearings/index.html)

How bearings work (http://science.howstuffworks.com/bearing.htm)Early bearing failure detection (http://www.reliableplant.com/Read/260/bearing-failure-detection)

How to measure a bearing (http://www.bearing-king.co.uk/how-to-measure-a-bearing.php)Kinematic Models for Design Digital Library (KMODDL) (http://kmoddl.library.cornell.edu/index.php) -

Movies and photos of hundreds of working mechanical-systems models at Cornell University. Alsoincludes an e-book library (http://kmoddl.library.cornell.edu/e-books.php) of classic texts on mechanicaldesign and engineering.

Types of bearings, Cambridge University (http://www.msm.cam.ac.uk/phase-trans/2010/types/index.html)

Some Observations of the Detection of Rolling Element Bearing Outer Race Fault(http://glassfish.idrsolutions.com:8282/HTML_Page_Extraction/output/3eef9907499fbf35852d78afa17f/

BearingOuterRace/index.html)The Effect of Frequency Resolution in Bearing Fault Studies

(http://glassfish.idrsolutions.com:8282/HTML_Page_Extraction/output/39e175067c1022abb68ba6f4eb00/BearingsFrequencyResolutionStudy/index.html)Diagnosis of Rolling Element Bearing Faults Using Envelope Analysis

(http://glassfish.idrsolutions.com:8282/HTML_Page_Extraction/output/3eef9907499fbf35852d78afa17f/EnvelopeAnalysisBPS/index.html)

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