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

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Presentation Transcript
slide1

Chapter 14

Bearings

/www2.chicago-rawhide.com

www.traxxas.com

www.continentalconveyor.com

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
slide4

2 TYPES OF ROLLING BEARINGS

I. Ball Bearings

II. Roller Bearings

i ball bearing
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

ball bearings
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
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 bearings8
Types of Ball Bearings
  • Double Deep Groove
    • Increases radial load
types of ball bearings9
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 bearings10
Types of Ball Bearings
  • Thrust Bearings
    • Used in applications with significant thrust load

http://kianho.com

types of ball bearings11
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
HOW It’s MADE:

http://www.youtube.com/watch?v=eGyoMuE4gDQ

http://www.youtube.com/watch?v=k8SHKy5tXbI&feature=related

ii roller bearings
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
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 bearings15
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 bearings16
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 bearings17
Types of Roller Bearings
  • Thrust Roller Bearings
    • Used in applications with significant thrust load

www.timken.com

mounted bearings
Mounted Bearings

Precision machine elements such as transmissions, reducers, right angle drives usually incorporate un-mounted bearings

other types of 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 bearings21
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/

slide23

Ball Joint – 3 rotational DOF

HEIM Bearing

See heim overview powerpoint

v 22 osprey
V-22 OSPREY

www.lordmpd.com

PitchChange Bearing

PendulumSpring

Hub Spring Set

Drive Link

Downstop

GimbalBearing

CentrifugalBearing

InboardBeam

PitchChange System

Outboard Spindle

hcl components of v 22 osprey
HCL Components of V-22 Osprey

Drive Link

Centrifugal Bearing

www.lordmpd.com

selecting bearings
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!

selecting bearings cont d
Selecting Bearings Cont’d

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

slide30

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.

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

Inner race rotates, then Pd = P = V*R where V = 1.0 if inner race rotates and V = 1.2 if outer race rotates.

Lar = CR * L10

Washing machine example, what if want 99% reliability??

3. What if thrust load is present??? - iteration

slide34

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

slide35

FIND R,T

Usually get for shaft analysis

START

ASSUME Y

~1.5 *Must initially guess

P=VXR+YT

C=PdfL/fN

Figure 14-12

Select Bearing

Table 14-3

Compute T/Co

Find e

Table 14-5 Iterate within reason

NO

YES

FIND Ynew

Ynew=Yold?

T/R>e?

NO

YES

P=VR

END

C=PdfL/fN

Select Bearing

END