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Thread: Fluid bearings in cars

  1. #1
    Associate Engineer
    Join Date
    Apr 2017
    Posts
    2

    Post Fluid bearings in cars

    Hi,

    I don't get the fluid bearing quite right - at least that's what I'm thinking.

    As far as I know, crankshafts (in engines) have hydrodynamic fluid bearings. If I look at the fluid wedge e.g.

    and the pressure, I don't understand how the shaft can be kept at the center position in case of fast acceleration and sudden braking of the car as well as driving over (e.g.) damaged roads that will vigorously shake the car (and therefore the shaft?).

    As far as I know, a bearing with two inlet ports is not used as here specified:



    So, anyone can tell me how it's done?

    Best wishes,
    Thomas
    Attached Images Attached Images

  2. #2
    Lead Engineer
    Join Date
    Aug 2013
    Location
    Houston TX USA
    Posts
    375
    supply pressure and lubricant film strength and the internal operational loadings for which the bearings are designed exceed any inertial loadings from external forces.

  3. #3
    Associate Engineer
    Join Date
    Apr 2017
    Posts
    2
    Hi,

    Thanks. Then I don't get these images: https://upload.wikimedia.org/wikiped...%2Bstat%29.jpg

    Why is it only a small portion (in blue) in the picture at the top?

    Best wishes,
    Thomas

  4. #4
    Project Engineer
    Join Date
    May 2015
    Posts
    70
    The rotating shaft actually drags the oil into that pressure area that you show. That pressure area is 'hydrodynamic lubrication' and can support a very considerable load. The main function of the oil pump pressure is to replace the oil in the bearings that is lost at each end and to keep lubricant flowing in order to remove heat from the components.

    It is the viscosity of the fluid that is responsible for the separation of the bearing surfaces

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