[python] Re: pivot quality

I was looking over various pivot designs on all the Phyton bikes and was 
wondering about the aircraft type rods they look pretty simple to consruct 
but.is there any info on how they work and hold up I relize aircraft spec parts 
are extremly strong but they were never inteaded to be use as pivot bearings 
under so much weight is that a proplem?
  ----- Original Message ----- 
  From: Torben Scheel 
  To: python@xxxxxxxxxxxxx 
  Sent: Tuesday, April 10, 2007 11:42 PM
  Subject: [python] Re: pivot quality


  Hi Dirk! 


  It is ball bearings, right? Roller bearings is a lot better for the purpose, 
but the stress on the pivot _is_ extreme. I have not ridden my Python enought 
to say if the Flevopivot is better, but I'd expect it, even if it isn't 
designed for the tilting force. 
   
  As for the rust - you'll notice that a lot of the danish bikes is coated with 
a layer of a chemical (usually pigmentated) called "paint". It helps in some 
extent - the powder version is the toughest, but it kind'a limits your 
tinkering, when it's applied :-)

  Cheers,
  Torben

    -----Original Message-----
    From: dirk.bonne@xxxxxxx
    To: python@xxxxxxxxxxxxx
    Date: Tue, 10 Apr 2007 21:54:53 +0200
    Subject: [python] Re: pivot quality


    Hi Jürgen,

    To make a good photo of such a little thing is easier asked then done.
    It rises far above my abilities with the camera to make a photo of the
    small dents in the bearing cap. I attached my best result ---still
    better then some of the UFO photos but not a lot. With a little bit of
    good will on your side, you can see the dents at regular distances on
    the inner cap. I can easily feel the dents by going over the cap wall
    with my finger nail. The dents are nearly all around with some places
    are worse (I suspect the front or back). All the caps have dents.

    Now for the reason, I do not want to give the full fault to the
    bearings. I have mistreated them by heating them up (I did not braze on
    the shell directly, but I remember welding my handlebar tube on the
    frame while having the bearings in and that may have been near enough).

    Anyway I do not think this pivot solution is so neat: These bearings are
    not sealed, and even though I filled the pivot up with grease, there was
    still a lot of sand in it (I attached a photo of the pivot shell where
    you see the flimsy sealing solution I choose: just a spacer above and
    below). You can also see the rust: Denmark has not only a lot of sand it
    is also very salty...

    liebe Grüße,
    Dirk

    Jürgen Mages wrote:
    > Hej Dirk,
    >
    > did you use these bearings:
    >
    > http://dirkb.dnsalias.net/image/python/skf_7201B.half.jpg 
    >
    > As far as I remember, Eduardo from Brazil used the same
    > type of angular contact ball bearings (Schrägkugellager).
    >
    > If so, these pivot types are left for the choice:
    >
    >  - tapered roller bearings
    >  - rod end bearings
    >  - cartridge bottom bracket
    >
    > Could you please send us a photo of the destroyed bearings?
    >
    > Groetjes,
    > Jürgen.

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