[python] Re: pivot quality

Hey August,
you name it. I was thinking of such a pivot using "aircraft rods". I just didn't know, how they are called. :-) The idea was to use two of them in order to have an adjustable pivot angle without changing other aspects of the geometry. The lower bearing could be fixed and the upper one should be movable forth and back. 

www.aurorabearing.com/products/aerospace-military/aerospace-series/rod-ends/male/default.html
I am a little in doubt though that 2 "aircraft rods" will give sufficient strength/support. Therefore, I was thinking of using a ball bearing from a cars front wheel suspension as the lower bearing. Those bearings are very stable and carry 300 kg when the car is just standing still. The dynamic forces must be much higher. 

http://www.yatego.com/atv-schiffke/p,44c9c353c6afa,434630b1776d88_0,vw-traggelenk-vw

I think that should work.

cheers
Thomas
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: <mailto:torben@xxxxxxxxxx>Torben Scheel
To: <mailto:python@xxxxxxxxxxxxx>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>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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