traxxas

1. Bearings /www2.chicago-rawhide.com www.traxxas.com Prepared by Prof R. M. Dahekar www.continentalconveyor.com

2. 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

3. www.bharatpetroleum.com www.me.psu.edu

4. 2 TYPES OF ROLLING BEARINGS I. Ball Bearings II. Roller Bearings

5. 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

6. Ball Bearings How to Assemble -Inner race press fit onto shaft shoulder (FN1, FN2) -Assembly slides into housing (RC2) between outer race and housing

7. 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

8. Types of Ball Bearings • Double Deep Groove • Increases radial load

9. 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

10. Types of Ball Bearings • Thrust Bearings • Used in applications with significant thrust load http://kianho.com

11. 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

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

13. 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

14. Types of Roller Bearings • Spherical Roller Bearings • Centers inner race about shaft to avoid binding www.dclcorp.co.kr/image/Nachi3.jpg

15. 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

16. Types of Roller Bearings • Thrust Roller Bearings • Used in applications with significant thrust load www.timken.com

18. 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

19. 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/

20. Bearing Selection see sec 14.6 – 14.10:

21. 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!

22. 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

23. “2” = 200 series

24. PRACTICE PROBLEM 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.