ball bearing
TRANSCRIPT
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Chapter 14
Bearings
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
www.me.psu.edu
www.bharatpetroleum.com
2 TYPES OF ROLLING BEARINGS
I. Ball Bearings
II. Roller Bearings
• Ball Bearing– Incorporates hardened
steel balls– Steel balls geometrically
contact inner and outer race at a point
– This creates high stresses locally
www.duratrax.com
I. Ball Bearing:
cage
seals Inner race
Outer race
Ball Bearings
How to Assemble
-Inner race press fit onto shaft shoulder (FN1, FN2)
-Assembly slides into housing (RC2) between outer race and housing
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
Types of Ball Bearings
• Double Deep Groove– Increases radial load
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
Types of Ball Bearings
• Thrust Bearings– Used in applications
with significant thrust load
http://kianho.com
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
HOW It’s MADE:
1. http://www.youtube.com/watch?v=eGyoMuE4gDQ
2. http://www.youtube.com/watch?v=k8SHKy5tXbI&feature=related
II. Roller Bearings
• Roller Bearings– Hardened steel cylindrical rollers– Line contact deforms into areas larger then
ball bearings– Capable of carrying higher radial loads
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
Types of Roller Bearings
• Spherical Roller Bearings– Centers inner race about
shaft to avoid binding
www.dclcorp.co.kr/image/Nachi3.jpg
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
Types of Roller Bearings
• Thrust Roller Bearings– Used in applications
with significant thrust load
www.timken.com
Mounted Bearings
Precision machine elements such as transmissions, reducers, right angle drives usually incorporate un-mounted bearings
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
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/
Ball Joint – 3 rotational DOF HEIM Bearing
See heim overview powerpoint
V-22 OSPREYDrive LinkDrive Link Hub Spring SetHub Spring Set
PendulumPendulumSpringSpring
PitchPitchChange BearingChange Bearing
GimbalGimbalBearingBearing
Outboard SpindleOutboard SpindleCentrifugalCentrifugal
BearingBearingInboardInboardBeamBeam
PitchPitchChange SystemChange System
DownstopDownstop
www.lordmpd.com
HCL Components of V-22 Osprey
Drive Link
Centrifugal Bearing
www.lordmpd.com
Bearing Selection see sec 14.6 – 14.10:
Selecting Bearings
Load-Life Relationship:
k
P
P
L
L
2
1
1
2P1 = load 1, L1 = life at load 1,
k = 3.00 for ball bearingsk = 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!
Selecting Bearings Cont’d
k
P
P
L
L
2
1
1
2Most manufacturers specify basic dynamic load rating, C, which is the load that results in 106 cycles. So, this equation can be rewritten as:
610k
dd P
CL
= Design Life for your
specific application for a design load of Pd
k
dd
LPC
/1
610
= Required dynamic load
rating for a design life = Ld
Note, these are all L10 lives!!! Which is the life for 90% reliability
“2” = 200 series
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 @ 3 loads per day, 30 minute cycle time/load.
Can use charts shown in 14-12 to get C. Or equation presented earlier.
CAREFUL!
• Previous equations assumes: L10 life, and inner race rotates and radial load only!!
1. Inner race rotates, then Pd = P = V*R 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
P = VXR + YT
P = Load
V = Rotation Factor (1.0 – Inner Race, 1.2 – Outer Race)
X = Radial Factor (.56 if Y>0)
R = Applied Radial Load
Y = Thrust Factor
T = Applied Thrust Load
*Thrust Load Present – Deep Groove Ball Bearing
START FIND R,T
ASSUME Y
P=VXR+YT
C=PdfL/fN
Select Bearing
Compute T/Co
Find e
T/R>e?
P=VR
C=PdfL/fN
Select Bearing END
FIND YnewYnew=Yold?
END
Figure 14-12
Table 14-3
YES
NOYES
NOTable 14-5 Iterate within reason
Usually get for shaft analysis
~1.5 *Must initially guess