[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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