O.S. 1.4 RX bearings

[Dave Smith]

Matt:   I just changed the rear bearing after 80 flights. I was curious as to its' condition.  No after run oil was used at all,and the bearing was in apparently good shape.

I found it interesting that the replacement bearing (from O.S.) had nary a number or letter on it.   Also it was packed with grease,and either the seals had been removed,or never installed in the first place,as the outer race was recessed for seals.   A friend found the same when he bought a replacement bearing.

A commercial industrial bearing supply house might be able to produce a bearing with larger balls,and thinner races,as per your suggestion.

Regards,,,,,,,,,,,,,Dave
  ----- Original Message ----- 
  From: Rcmaster199 at aol.com 
  To: discussion at nsrca.org 
  Sent: Friday, July 04, 2003 7:32 PM
  Subject: Re: O.S. 1.4 RX bearings


  Bob,

  RPM and load are the killers of bearings, all else being equal. Larger props turning lower rpm should help the problem but the greater load does not. 

  I think dave hit it on the head: The OS bearing was intended for a smaller engine designed to turn a smaller load at the same rpm. 

  The 140 should be using a larger bearing with proportionately larger ball bearings . These in turn, would spin at proportionately slower rates when the engine is at speed, and their larger size would distribute the load better.

  In the meantime, I recommend that someone out there who uses the engine should try to find a bearing that uses thinner races and larger ball bearings. It's the smallish ball bearings turning too fast due to their small diameter, in the standard bearing, that wear out under the load of the 140.

  Another approach is what 3M Mintors have: two main bearings that look the same as the OS 140 bearing (but I have not actually measured these). The idea is better load distribution, but nothing is really being done about the rpm the balls are turning. 

  Overall, I prefer the WEBRA approach: Larger bearing all the way around. I expect the bearing to last for years.

  Matt Kebabjian



    Subj:Re: O.S. 1.4 RX bearings 
    Date:7/4/2003 3:45:17 PM Eastern Daylight Time
    From:rcaerobob at cox.net
    Reply-to:discussion at nsrca.org
    To:discussion at nsrca.org
    Sent from the Internet 



    Those of us who ran the old OS 61 RF's, pumped or not, remember when bearings lasted forever....UNTIL we started putting high pitch, high diameter props on the beasts.
        Now, we've just added more pitch and diameter over the years, and my experience has been that bearing life relates directly to those factors.  Of course lubrication, and moisture, certainly contribute, but most bearings I've dissassembled have had the balls and races brinnelled and beaten to death.  
        That starts plating flaking, and eats things...it could just be coincidence that they rust, too....

    Bob Pastorello, Oklahoma
    NSRCA 199, IMAC 1320, AMA 46373
    rcaerobob at cox.net
    www.rcaerobats.net




      ----- Original Message ----- 
      From: mdarr00 at comcast.net 
      To: discussion at nsrca.org 
      Sent: Friday, July 04, 2003 2:43 PM
      Subject: Re: O.S. 1.4 RX bearings


          Dave, I could not agree with you more!

      Mike Darr


        ----- Original Message ----- 
        From: Dave Smith 
        To: discussion at nsrca.org 
        Sent: Friday, July 04, 2003 3:22 PM
        Subject: Re: O.S. 1.4 RX bearings


        Verne:   Based on my experience with the YS .60 & .61 two strokes,the grease will disappear very soon,even with two seals intact. 
        I don't think lubrication is the problem,or the cure.  The rear bearing is just too small.

        It seems this size bearing started out in life as the bearing for the 1.08.   It makes no sense to me that a bearing for a rather mild 1.08 would stand up to the rigors of a 1.40.

        Good luck,,,,,,,,,,,,,Dave








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