Re: [CR] Length of head tube and brinelling

(Example: Framebuilders:Norman Taylor)

From: "Jon M. Crate" <Jon@FAI.US>
To: <classicrendezvous@bikelist.org>
References: <001801ca6cf7$9094c030$b1be4090$@com>
Date: Tue, 24 Nov 2009 10:03:35 -0500
Organization: FAI Materials Testing Laboratory
Thread-Index: Acps94++3yZ2FHR/T3yKJ48dw6G6GQAGkkag
In-Reply-To: <001801ca6cf7$9094c030$b1be4090$@com>
Subject: Re: [CR] Length of head tube and brinelling


Don is onto something. And they say the bigger they are the harder they fall. With larger frames, often, come larger riders that weigh more and therefore more loading. If 5 or 10% more balls distribute the forces, consider the weight differential of riders is even larger.

I've also been watching the thread as a materials scientist and as the analogy of the blind describing the elephant, and as is often the case in great debates, there are elements of truth to each argument.

I would say, hardness matters, adjustment matters, design matters, alignment matters, flexibility/stiffness matters, loading (preloading already mentioned in adjustment), and lubrication matters. For long problem free life, everything must be done correctly and there are a large number of ways to go astray. I see this everyday in my work.

In the end, imo, Brinelling, while it is a word, is not what is generally causing these issues, Jobst is correct, it is essentially fretting wear. Bottom brackets do not suffer the same fate because they are rotating which distributes the wear and distributes the lubrication. These headsets, as described earlier, suffer incessant vibration, rarely rotate, and even if surrounded with lubrication, the loaded surfaces are not well lubricated, wear particles accumulate and oxidize producing excellent abrasive materials which remain on site to further their cause of pitting.

So one lesson, in addition to correct alignment, adjustment, and lubrication is to distribute the lubrication by rotation periodically.

Jon Crate getting ready for his first interstate ride over the holiday in Marietta, GA

-----Original Message----- From: classicrendezvous-bounces@bikelist.org [mailto:classicrendezvous-bounces@bikelist.org] On Behalf Of Tom Sanders Sent: Tuesday, November 24, 2009 6:16 AM To: classicrendezvous@bikelist.org Subject: [CR] Length of head tube and brinelling

I think Don Gillies may be onto something relating brinelling to head tube length. I sat here during this thread wondering why have I never had a headset problem? I've adjusted many, and never once had any problems with them. Lord knows it is not because of any special mechanical ability on my part. I am the most mechanically inept person around. I just tighten them until they feel a bit tight and then back them off until they feel good and there is no rattle up there. I was thinking it was sheer luck on my part. Now I am thinking it is because perhaps I ride smaller bikes? Is this just coincidence or does this brinelling occur mostly on larger bikes?

Tom Sanders

Lansing, MI USA