Re: [CR]Re: cup and cone wear (not just on Motobecane)

(Example: Framebuilders:Tony Beek)

From: "ternst" <ternst1@cox.net>
To: <john@os2.dhs.org>, <classicrendezvous@bikelist.org>
References: <BAY101-F20A131FC27A88A1C8C9A1AD6300@phx.gbl> <4500387F.4040004@new.rr.com>
Subject: Re: [CR]Re: cup and cone wear (not just on Motobecane)
Date: Thu, 7 Sep 2006 12:01:39 -0700
reply-type=original

What's the proper sequence / level of hardness between ball bearing, cup, and cone? Which is hardest then on down to softest for ease of replacement and cost?
Ted Ernst
Palos Verdes Estates
CA USA


----- Original Message -----
From: John Thompson
To: classicrendezvous@bikelist.org
Sent: Thursday, September 07, 2006 8:19 AM
Subject: Re: [CR]Re: cup and cone wear (not just on Motobecane)



> Reid Fisher wrote:
>
>> You metallurgists: what's the mechanism (at the micro scale) for
>> pitting? Does it start at some kind of micro-irregularity in the
>> bearing where stress is concentrated?
>
> According to Jobst Brandt, the pitting is caused by fretting due to
> lubrication failure. In the absence of effective lubrication,
> microscopic welds form between the balls and the cones; when these are
> torn apart by rotation of the wheel, pieces of the cone material come
> with it, leaving a pit. Once a pit forms, it will tend to grow and spread.
>
> --
> John (john@os2.dhs.org)
> Appleton WI USA