More than you ever wanted to know about brake pads_ by liuqingyan


									More than you ever wanted to
  know about brake pads!

   Jon BeVier, Chris Brazell, Sam Tipton, Wesley Holleman
                       Engineering 45
                 Santa Rosa Junior College
             The history of brake pad
   • Wood Brake pads
      – Often splintered wood
      – Wood would not adhere to
        contact surface if burnt by heat
      – Used on wagons of the west
      – Would wear down tires on

***Your new car with wooden brakes =….***
               Brakes of the 20th century
• Initial copper brake pads
   – Stopping distance better than wood
   – Harder to make
   – Lasted longer than wood

  •Asbestos brake pads
      •Developed not to long after copper
      •Lasted longer than copper
      •HARMFUL brake dust
   Current brake pad technology
• Composed of a variety of materials
   – Copper, aluminum, ceramic compounds
   – Kevlar, polymers, resins, carbon fiber, other
• Broad range of applications
   – Racing
   – High load
   – Daily Use

                                         •Variety of shapes and sizes for
                                             •Disk brakes
                                             •Drum brakes: air powered,
                                             hydraulic powered.
             Brake Pad Composition
• Ceramic brake composition
    Ceramic brakes include trace amounts of
    copper and other metals to create a longer
    lasting brake pad. They use resin and other
    polymers for filler and to create a higher
    coefficient of friction at high temperatures.

•    Carbon fiber brake composition
      Carbon fiber brakes use the same
      fillers as ceramic brakes however
      carbon fiber brakes create more dust
      and last longer. In the case of carbon
      fiber brakes the filler is what
      determines the noise level and life of
      the brake pad. Felt fillers make less
      noise than epoxy fillers.
   Brake pad compression analysis
• Heated organic ceramic pads @ 300C for 2,4,and 8 minutes with 1
  control pad.
• Compressed pads with Tinius Olsen Materials testing machine.
Results of Compression
       What does this MEAN????
  I’ll tell you what it could mean!
• The unheated pad showed its ability to give with the
  compression of the machine, no heat means the
  materials inside do not fuse together.

• The two minute pad BARELY compressed, perhaps due
  to the composition and heat reactivity of the materials

• The four and eight minute pads could have exceeded the
  correct level of heat for this composition, thus the
  materials inside start to “carbonize”, or burn, and the pad
  starts breaking apart.
Pictures of our different brake pads
•   All of our pads looked the   Before compression:
    same after compression.
    The Non-recoverable
    compression in each is
    as follows:

                                 After Compression:

    No heat – 14/1000”
    2mins@300C – 11/1000”
    4mins@300C – 10/1000”
    8mins@300C – 16/1000”
    Heat Cycles of brake pads
• Brakes are subject to heat cycles as cars
  apply pressure to the brake lever
  Current brake pad limitations
• Everything has a limit, Brakes have some limits
• Manufacturers will post temperature ranges for
  operation. Anything above this temperature and
  the brake pad will carbonize.
• Metal on metal contact causes warping if not
  “broken in” correctly, all manufacturers give
  “breaking in” instructions. This allows the brakes
  to conform to the brake disc/drum and heat up
  and cool down a few times to “set” the materials
  inside the brake pad.
Manufacturer’s posted limits and maximum coefficients of friction
         Brakes of the future
• New Compounds
  – Companies are always working on new
    compounds that will make brakes quieter,
    produce less dust, last longer, and stop faster.
  – The leading edge of brakes generally starts in
    racing and works its way into industrial
• But compounds can only take us so far…
           Electromagnetic Brake
• Consists of non-linear
  magnetic steel plate, a
  permanent magnet and a
  current coil.
• The coil generates a magnetic
  field which acts against the
  field of the permanent magnet.
  The brake is applied when the
  coil current is zero. Increasing
  the coil current will release the
  brake. The braking force can
  be calculated as a function of
  the coil current.
  Electromagnetic brake (cont.)
• With no friction, heat would be minimized,
  there is nothing to burn up or be sheared
  off to make dust or shorten the life and no
  contact to make noise
• Current applications
  – Rollercoasters
  – Industrial machinery
     • Brakes
     • clutches
•   Pictures:

•   Information:

To top