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would you use this crank???

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    #16
    Originally posted by digger View Post
    I don't agree with (1) as heavily loaded journals require a lower RA

    (3) to add to this cast cranks b25 and eta require specific grinding and polishing rotational directions where forged steel not so much
    alright, I'll step away from google and try to use my head regarding #1... just want to get it. My understanding of the crank riding on the bearing covered by the oil film is like tire hydroplaning on water: less tire tread (smoother) = more hydroplaning (good in the crank case). But there are probably some limitations due to clearances, oil type, oil pressure...

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      #17
      the smoother it is, the thinner the oil film can get (more load capacity) before you get metal to bearing contact because the peaks on the surface are genrally smaller. note that RA doesn't explicitly define the peaks but its the most common used. when people look at honing there are a whole bunch of other terms to properly define the surface valleys and peaks

      Smoother also does less damage to the bearing on cold/dry start where the oil isnt flowing very well yet or you have lack of lubricaton from giving the engine too much rpm and load with cold (thick) oil

      some places also do REM and super finished cranks but that has other benefits besides journal performance
      Last edited by digger; 03-23-2017, 05:49 PM.
      89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

      new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

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