Brakes

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Brakes

  1. 1. Brakes
  2. 2. Types <ul><li>Parking Brake </li></ul><ul><li>Service Brake </li></ul><ul><ul><li>Hydraulic </li></ul></ul><ul><ul><ul><li>Disc Brakes </li></ul></ul></ul><ul><ul><ul><li>Drum Brakes </li></ul></ul></ul><ul><ul><ul><li>Dual System </li></ul></ul></ul><ul><ul><li>Antilock Brake System (ABS) </li></ul></ul>
  3. 3. Play Principles of Braking
  4. 4. Brake System Principles <ul><li>Kinetic Energy </li></ul><ul><li>Mass </li></ul><ul><li>Weight </li></ul><ul><li>Speed </li></ul><ul><li>Inertia and Momentum </li></ul>
  5. 5. Coefficient of Friction Video
  6. 6. Parking Brake <ul><li>Not an “Emergency” Brake </li></ul><ul><li>Used specifically to keep a parked vehicle from moving </li></ul><ul><li>Usually on rear wheels only </li></ul><ul><li>Mechanically operated </li></ul><ul><ul><li>Static Friction: at rest friction- More friction </li></ul></ul><ul><ul><li>Kinetic Friction: in motion friction- less friction </li></ul></ul>
  7. 7. Typical Parking Brake
  8. 8. Play Parking Break Video
  9. 9. Play Parking Brake Adjustment Video
  10. 10. Service Brakes <ul><li>Primary Braking System </li></ul><ul><li>Should be stronger than the engine </li></ul><ul><li>Hydraulic Operated </li></ul><ul><ul><li>Can be Vacuum, Hydro or Motor assisted </li></ul></ul><ul><ul><li>Disc System </li></ul></ul><ul><ul><li>Drum System </li></ul></ul><ul><ul><li>Dual System </li></ul></ul>
  11. 11. Typical System
  12. 12. Hydraulic Principles <ul><li>Fluids cannot be compressed </li></ul><ul><li>Fluids can transmit Movement </li></ul><ul><ul><li>Acts “Like a steel rod” in a closed container </li></ul></ul><ul><ul><li>Master cylinder transmits fluid to wheel cylinder or caliper piston bore. </li></ul></ul><ul><li>Fluids can transmit and increase force </li></ul><ul><ul><ul><ul><li>Force </li></ul></ul></ul></ul>Area Pressure
  13. 13. Hydraulics <ul><li>Simplified Hydraulic Brake System </li></ul><ul><li>Drum Brake </li></ul><ul><li>Master Cylinder </li></ul><ul><li>Disk Brake </li></ul>
  14. 14. Hydraulic pressure is distributed equally in all directions
  15. 15. Same line pressure to all wheels
  16. 16. The Hydraulic pressure is the same, but the applied force can be changed by the piston size
  17. 18. The applied pressure can be raised or lowered by piston size
  18. 19. Play Hydraulic Pressure Video
  19. 20. Brake Pedal Design Advantage by Leverage <ul><li>First Mechanical Advantage is Driver’s foot </li></ul><ul><li>Length of Lever determines force applied </li></ul><ul><li>Uses Fulcrum </li></ul><ul><li>Pedal Ratio </li></ul>10 2 5:1 2.5 inches 5 0.5 inch
  20. 21. Play Break Pedal Leverage Video
  21. 22. System Basics <ul><li>Hydraulic actuation allows multiplication of pedal force. </li></ul><ul><li>In this system, a 10lb force on the pedal produces 360 lbs of force at the friction surface. </li></ul>
  22. 23. Play Break Lines & Hose Video
  23. 24. Brake Fluid <ul><li>Properties of Brake Fluid </li></ul><ul><ul><li>Does not thicken or then with changing heat </li></ul></ul><ul><ul><li>Must not boil </li></ul></ul><ul><ul><li>Must be compatible with brake parts material </li></ul></ul><ul><ul><li>Must lubricate internal parts </li></ul></ul><ul><ul><li>Must not evaporate easily </li></ul></ul>
  24. 25. Brake Fluid types <ul><li>DOT 3 and 4- </li></ul><ul><ul><li>Polyglycol based </li></ul></ul><ul><ul><li>Most common </li></ul></ul><ul><ul><li>Compatible with one another </li></ul></ul><ul><ul><li>Inexpensive </li></ul></ul><ul><ul><li>Destroys paint </li></ul></ul><ul><ul><li>Ruined by moister </li></ul></ul><ul><li>DOT 5- </li></ul><ul><ul><li>Silicone Based </li></ul></ul><ul><ul><li>Used only for heavy duty applications </li></ul></ul><ul><ul><li>Not Compatible with 4&5 </li></ul></ul><ul><ul><li>Very Expensive </li></ul></ul><ul><ul><li>Does not damage paint </li></ul></ul>DOT= Department of Transportation High #= High stands, quality and boiling point
  25. 26. Fluid Contaminates <ul><li>Moister- Lowers boiling point </li></ul><ul><ul><li>water boils @ 212*F DOT 3 boils @ 401*F </li></ul></ul><ul><li>Petroleum Based Product- </li></ul><ul><ul><li>soften rubber parts causing swelling </li></ul></ul><ul><li>Dirt & Debris- </li></ul><ul><ul><li>causes corrosion and clogs </li></ul></ul><ul><li>Air and Vapors- </li></ul><ul><ul><li>Compressible prevents pressure from reaching brakes </li></ul></ul>
  26. 27. Play Break Fluid Video
  27. 28. Master Cylinder <ul><li>Provides a reservoir for brake fluid and contains the driving pistons in the hydraulic circuit </li></ul><ul><li>2 Types </li></ul><ul><li>Front - Rear split </li></ul><ul><li>-One piston for front brakes and one for rear </li></ul><ul><li>-If a leak occurs you could lose front brakes </li></ul><ul><li>Diagonally split </li></ul><ul><li>-One piston drives one front wheel and one rear wheel </li></ul><ul><li>-Diagonal layout allows you to maintain directional control if a leak occurs </li></ul>
  28. 29. Play Tandem Master Cylinder Video
  29. 30. Play Divide System Video
  30. 31. Power Booster in closed position
  31. 32. Play Power Booster Video
  32. 33. Drum Brakes <ul><li>Expanding shoes create force on the inner surface of the drum </li></ul><ul><li>Used on the rear of some trucks and SUV’s </li></ul><ul><li>Self-energizing design requires less activation force </li></ul><ul><li>Require periodic adjustment </li></ul>
  33. 34. Drum Brake System
  34. 35. Vented Rotors Vented Rotors have Fins in the spaces between their machined surfaces. These spaces allow air to pass through, which helps carry heat away.
  35. 36. Nonvented Rotor Non Vented Rotors are used on smaller vehicles, and have no cooling fins
  36. 37. Play Brake Disc Video
  37. 38. Disc Brake Caliper Assembly
  38. 39. Caliper Types <ul><li>There are 2 types of Calipers </li></ul><ul><li>Fixed </li></ul><ul><ul><li>Calipers are disc brakes that use a caliper that is FIXED in position and does not slide. They have pistons on both sides of the disc. There may be 2 or 4 pistons per caliper </li></ul></ul><ul><li>Floating </li></ul><ul><ul><li>Much more common </li></ul></ul><ul><ul><li>Single Piston </li></ul></ul><ul><ul><li>Easier to work with </li></ul></ul><ul><ul><li>On “inboard” side of caliper </li></ul></ul>
  39. 40. Fixed Caliper <ul><li>Motorcycles and some import trucks and cars use this type </li></ul><ul><li>Similar to bicycle brakes </li></ul>
  40. 41. Sliding Caliper <ul><li>Applies pressure to two pads on opposite sides of rotor </li></ul><ul><li>Caliper </li></ul><ul><ul><li>Sliding </li></ul></ul><ul><ul><li>Fixed </li></ul></ul><ul><li>Friction Material exposed to air </li></ul>
  41. 42. Fixed Caliper <ul><li>Applies two pistons to opposite sides of rotor </li></ul><ul><li>Caliper stays stationary </li></ul><ul><li>Disc Brakes require higher hydraulic pressure </li></ul>
  42. 43. Play Disc Brake Calipers Video
  43. 44. Diagnosis Several different types of Complaints Noise Pulsation Pedal travel More later…
  44. 45. Brake Noise Wear Indicator
  45. 46. Brake Pulsation Usually a warped Rotor Rotor needs trued on a brake lathe
  46. 47. Pedal Travel NO BRAKES!!!! <ul><li>Excessive pedal travel </li></ul><ul><li>Pedal feels soft and squishy </li></ul><ul><li>Requires excessive effort to stop vehicle or my cause brakes to not function at all </li></ul>
  47. 48. Play Drum Brake Inspection Video
  48. 49. Play Disc Brake Inspection Video
  49. 50. Anti-Lock Brakes <ul><li>A locked (sliding) wheel offers less braking force than a decelerating rolling wheel </li></ul><ul><li>The locked wheel also produces little lateral force, preventing steering control </li></ul><ul><li>Anti-Lock systems (ABS) monitor wheel lock-up and modulate brake pressure to provide controlled braking under most circumstances </li></ul>
  50. 51. Play ABS Principles Video
  51. 52. Anti-Lock Brakes <ul><li>System can have 2, 3 or 4 channels </li></ul><ul><li>Trucks typically use 3 channel with only one sensor for the rear axle </li></ul><ul><li>Most modern cars use 4 channel system </li></ul><ul><li>Wheel speed sensors monitor each wheel speed </li></ul><ul><li>ABS controller and high-pressure pump increase or reduce pressure to wheels in order to maintain consistent wheel speeds </li></ul>
  52. 53. Play ABS video
  53. 54. Play Drum, Disc, & ABS Video
  54. 55. Other Braking Systems <ul><li>Air Brakes </li></ul><ul><li>Exhaust Brakes </li></ul><ul><li>Electric or Trailer Brake </li></ul>
  55. 56. Play Disc Brake Replacement Video
  56. 57. Play Replacing The Rotor Video
  57. 58. Play Drum Brake Replacement Video

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