# Vibration Diagnostics - PowerPoint PPT Presentation

Vibration Diagnostics

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Vibration Diagnostics

## Vibration Diagnostics

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##### Presentation Transcript

1. Vibration Diagnostics Vibration Diagnostics Vibration Diagnostics Vibration Diagnostics Why Wheel Balancing?

2. What is Vibration? Vibration? Vibration? Vibration?

3. In order to Diagnose a Vibration we must understand some... Basic Principles

4. 1st cycle 2nd cycle What is a cycle? 1 second in time 2 cycles per second or 2 Hz

5. Frequency 1 second in time 1st cycle 2nd cycle Frequency is 2 CPS or 2 Hz

6. 1 second Tire Imbalance With a Frequency of 4 Hz Imbalance 4 Revolutions = Frequency of 4 CPS/Hz

7. Amplitude of Force 1 second 6 Hz Tire Imbalance If the Frequency increases... so does the amplitude of force Imbalance

8. Reed Tachometer can identify Frequency 500 250 100 25 Hz

9. "Steering Wheel Shake" Wobble Shimmy Waddle

10. "Steering Wheel Shake" 5 to 20Hz

11. What is Static Balance? Static Balance is when the weight of the wheel and tire assembly is distributed equally around the axis of the wheel rotation. If static Balance exists the wheel will have no tendency to rotate. If rotated it rotates with Equal Force

12. How do we Balance this Wheel? Heavy Area Rotates to Bottom .25 oz Imbalance

13. Is this wheel in static balance? .25 oz imbalance .25 oz weight added

14. If this wheel is in perfect balance at a speed of 40 mph, will it remain in balance at all speeds? .25 oz imbalance .25 oz weight added

15. Yes, the is the word “Perfectly”

16. .86 lbs .86 lbs At 20 MPH .25 ounces of imbalance generates .86 pounds of force Imbalance in Tire Balance Weight Applied

17. 10.5 lbs. 10.5 lbs. At 70 MPH .25 ounces of imbalance generates 10.5 pounds of force

18. At 70 mph the force is 10.53 pounds It's still in perfect balance! 10.53 lbs. NOTE: Speed rated Tires Utilize a Nylon Over-lay to prevent tire distortion at high speeds. 10.53 lbs.

19. Common Problems: • Round Off vs. Fine Mode • Mounting • Clean Mounting Surface • Excessive Runout • Tolerance stack up

20. Consider this... Most Computer Wheel Balancers Round off to the nearest .25 oz. 1 oz. Balance Weight 1.12 oz. Imbalance Is this a Problem?

21. 1.12 ounces Imbalance .25 Round Off = .12 Error 1 oz. Balance Weight 1.12 oz. Imbalance Is this a Problem?

22. On most cars, this Slight Imbalance would not be felt, however "My Car Vibrates at 55 MPH"

23. Why Does it Vibrate at One Speed? RESONANCE

24. To Understand Resonance, you must understand an objects Natural Frequency Mechanical Objects have there own Natural Frequency

25. 1 second Tire Imbalance With a Frequency of 4 Hz Imbalance 4 Revolutions = Frequency of 4 CPS/HZ

26. Amplitude of Force 1 second 6 Hz Tire and Wheel Frequency increases... with Speed Imbalance

27. Suspension Natural Frequency Range from 10 - 15 Hz/CPS 14 Hz 12 Hz

28. Suspension Frequency Tire & Wheel Frequency Sum of Tire & Wheel Beating - & - Phasing

29. Vibration at One Speed 1st order harmonic 15 10 5 0 10 20 30 40 50 60

30. "...But I balanced the tires in the fine mode and... ... it still vibrates at 55 MPH"

31. If a Tire and Wheel assembly is square, can it be balanced to Zero? Yes, balance only refers to force

32. Are Tires and Wheels Perfectly Round?

33. Center Hole -or- Lug Circle... can be off-center as much as .010”

34. 95% of O.E.M wheels are Hub-centric & *100% through 1 Ton *(as of 1/1/00) Mounting Error Duplicate O.E.M. Mounting Hub-centric Are wheels centered by the center hole? Are wheels centered by the lug nuts? Lug-centric

35. Mounting Error Corvette Wheel Hub-centric

36. Tire High Spot Wheel High Spot Max assembly radial and lateral runout is .050” measured off the vehicle and .060” on the vehicle Note: Rule of thumb for passenger cars and light trucks Would this tire and wheel mismatch cause a problem?

37. One Revolution Radial Runout

38. 15 10 5 0 10 20 30 40 50 60 Runout Problem 1st order harmonics

39. Match Mounting Mis-Matched Matched

40. Match Mounting

41. Lateral Runout .045” Steel Wheel* .030” Aluminum* Radial Runout .040” Steel Wheel* .030” Aluminum* Wheel Runout Lateral and Radial * Reference GM

42. Radial Runout .040” Steel Wheel* .030” Aluminum* Wheel Runout Lateral and Radial Measure runout at bead seat area * Reference GM

43. Lateral Runout .045” Steel Wheel* .030” Aluminum* Wheel Runout Lateral and Radial Measure lateral runout at inside rim lip * Reference GM

44. Lateral Runout .050” Off Vehicle* .060” On Vehicle* Radial Runout .050” Off Vehicle* .060” On Vehicle* Assembly Runout Lateral and Radial * Reference GM

45. Radial Runout .050” Off Vehicle* .060” On Vehicle* Assembly Runout Lateral and Radial Tape * Reference GM

46. Lateral Runout .050” Off Vehicle* .060” On Vehicle* Assembly Runout Lateral and Radial * Reference GM

47. Dynamic Imbalance

48. Dynamic Imbalance 1 oz. Imbalance

49. During One Revolution

50. Responder = Steering Wheel "Shimmy"