www.traxxas.com

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Chapter 14 Bearings
/www2.chicago-rawhide.com
www.traxxas.com
www.continentalconveyor.com
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Bearings

• Function
• Carry load in one or several directions while
  allowing frictionless motion in other directions
• Fatigue F(Pressure, Velocity)
• 3 main types of Bearings
• Rolling Element Bearings
• Sliding Bearings
• Elastomeric Bearings

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www.bharatpetroleum.com
www.me.psu.edu
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2 TYPES OF ROLLING BEARINGS
I. Ball Bearings II. Roller Bearings
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I. Ball Bearing
Outer race

• Ball Bearing
• Incorporates hardened steel balls
• Steel balls geometrically contact inner and outer
  race at a point
• This creates high stresses locally

Inner race
seals
www.duratrax.com
cage
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Ball Bearings
How to Assemble -Inner race press fit onto shaft
shoulder (FN1, FN2) -Assembly slides into housing
(RC2) between outer race and housing
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Types of Ball Bearings

• Deep Groove Ball Bearings
• Primarily radial load carrying
• Thrust load equal to 25 of radial load
• Can get as large as 300K radial load capacity

http//my.ecplaza.net/nbsinobest/12l.asp
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Types of Ball Bearings

• Double Deep Groove
• Increases radial load

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Types of Ball Bearings

• Angular contact ball bearing
• Increased thrust load due to increase in lateral
  contact area between ball and race

www.hz-bearing.com
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Types of Ball Bearings

• Thrust Bearings
• Used in applications with significant thrust load

http//kianho.com
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Types of Ball Bearings

• Super precision ball bearings
• Nearly perfect spheres
• High surface finish
• Applications
• High speed grinding, milling, boring, routing
• No Vibration!!
• Ceramics
• Hard
• No deformation

www.timken.com
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HOW Its MADE

1. http//www.youtube.com/watch?veGyoMuE4gDQ
2. http//www.youtube.com/watch?vk8SHKy5tXbIfeature
   related

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II. Roller Bearings

• Roller Bearings
• Hardened steel cylindrical rollers
• Line contact deforms into areas larger then ball
  bearings
• Capable of carrying higher radial loads

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Types of Roller Bearings

• Needle Bearings
• 4 joint machine applications
• As the number of rollers goes up the greater the
  contact area
• The greater the contact area the greater the load

www.clworldwide.com
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Types of Roller Bearings

• Spherical Roller Bearings
• Centers inner race about shaft to avoid binding

www.dclcorp.co.kr/image/Nachi3.jpg
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Types of Roller Bearings

• Tapered Roller Bearing
• Support high thrust loads (wheel bearing)
• Supports radial load (car weight) while
  supporting thrust loads (cornering)
• Wheel rotates with little resistance/friction

www.ahrinternational.com
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Types of Roller Bearings

• Thrust Roller Bearings
• Used in applications with significant thrust load

www.timken.com
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Mounted Bearings
Precision machine elements such as transmissions,
reducers, right angle drives usually incorporate
un-mounted bearings
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Other Types of Bearings

• Thompson linear bearings
• Sliding Bearings
• No rolling elements
• Sleeve over shaft where sleeve acts like bearing
  (Generally higher friction)
• Bronze good material due to coefficient of
  friction, porosity and wear resistance

www.intbearing.com
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Other Types of Bearings

• Self Lubricating Bearings
• Low Friction
• No lubrication needed
• Elastomeric Bearings

www.garlockbearings.com
http//www.polygoncompany.com/
http//www.polygoncompany.com/
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Ball Joint 3 rotational DOF
HEIM Bearing
See heim overview powerpoint
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V-22 OSPREY
www.lordmpd.com
PitchChange Bearing
PendulumSpring
Hub Spring Set
Drive Link
Downstop
GimbalBearing
CentrifugalBearing
InboardBeam
PitchChange System
Outboard Spindle
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HCL Components of V-22 Osprey
Drive Link
Centrifugal Bearing
www.lordmpd.com
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Bearing Selection see sec 14.6 14.10
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Selecting Bearings
Load-Life Relationship
P1 load 1, L1 life at load 1, k 3.00 for
ball bearings k 3.333 for roller bearings
Example A ball bearing lasts 3,000 hours at 500
lb, how long will it last at 1,000 lbs? SIMPLE!
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Selecting Bearings Contd
Most manufacturers specify basic dynamic load
rating, C, which is the load that results in 106
cycles. So, this equation can be rewritten as
Design Life for your specific application for a
design load of Pd
Required dynamic load rating for a design life
Ld
Note, these are all L10 lives!!! Which is the
life for 90 reliability
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2 200 series
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Example A horizontal washing machine rotates at
1,100 rpm. Spec out bearings on ends if the
dynamic radial load is 400 lb and static load is
75 lb. Want machine to last 20 years _at_ 3 loads
per day, 30 minute cycle time/load.
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Can use charts shown in 14-12 to get C. Or
equation presented earlier.
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CAREFUL!

• Previous equations assumes L10 life, and inner
  race rotates and radial load only!!

1. Inner race rotates, then Pd P VR where V
   1.0 if inner race rotates and V 1.2 if outer
   race rotates.
2. Lar CR L10

Washing machine example, what if want 99
reliability??
3. What if thrust load is present??? - iteration
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P VXR YT
P Load
V Rotation Factor (1.0 Inner Race, 1.2
Outer Race)
X Radial Factor (.56 if Ygt0)
R Applied Radial Load
Y Thrust Factor
T Applied Thrust Load
Thrust Load Present Deep Groove Ball Bearing
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FIND R,T
Usually get for shaft analysis
START
ASSUME Y
1.5 Must initially guess
PVXRYT
CPdfL/fN
Figure 14-12
Select Bearing
Table 14-3
Compute T/Co
Find e
Table 14-5 Iterate within reason
NO
YES
FIND Ynew
YnewYold?
T/Rgte?
NO
YES
PVR
END
CPdfL/fN
Select Bearing
END