re: [CR]Cartridge Bearings


Example: Events:Cirque du Cyclisme:2004

Date: Thu, 24 Jun 2004 18:35:55 -0400
From: HM & SS Sachs <sachs@erols.com>
To: BobHoveyGa@aol.com, classicrendezvous@bikelist.org, Carb7008@cs.com
Subject: re: [CR]Cartridge Bearings


Bob Hovey's response to a question on the friction of cartridge bearings may carry an unwritten assumption that I suspect many of us share: Stiff bearing when twirled in the hand implies stiff under load. I got called on this decades ago by Jim Papadopoulos, and his chain of reasoning might go like this: Unloaded, the seal friction is the bigger part of the total friction. Loaded, it's more likely the bearing. There is no necessary connection between unloaded and loaded bearing friction or resistance to turning. Bob also raised another very interesting question for which I don't have an answer. Bot wrote:

I guess the best seal design would be the labyrinth seal (Maxicar?), where dirt is kept out by thin interleaved washers that do not actually touch. No contact, no friction, just a torturous zig-zag path that only the most determined dirt particle could navigate. +++++++ Now, if I reduce myself to the appropriate size so I can think like dirt and water droplets, I would think that Bob has a decent generalization, but... (1) A hydrophobic surface (grease, teflon) will tend to keep water beaded and OUT of the bearing. This is good. (2) Maybe I should be more worried about dry or oily particles in the silt-sized range, maybe 10 - 20 microns in size. These really would like close clearances to keep them out, and they are what can score (or polish).

But, if memory serves, keeping the water out is considered a primary virtue, to keep the grease from breaking down.

Please, Joe B-Z or someone, save me with some facts!

harvey sachs
mcLean va