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

(Example: Books:Ron Kitching)

Date: Tue, 05 Sep 2006 14:41:25 -0400
To: classicrendezvous@bikelist.org
From: "John Betmanis" <johnb@oxford.net>
Subject: Re: [CR]Re: cup and cone wear (not just on Motobecane)
In-Reply-To: <BAY101-F20A131FC27A88A1C8C9A1AD6300@phx.gbl>


At 05:52 PM 9/5/06 +0000, 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?

Not a metallurgist, but the satin "tracks" where the balls run would be normal wear. If you see any irregularities in the tracks that look like pits, that's when the cones are deteriorating. Pitting is when the metal starts to break apart after constant compression cycles and pieces break loose. Once a small pit develops, it will get bigger as more metal around it breaks away due to the increased load the remaining metal gas to bear.

John Betmanis
Woodstock, ON
Canada