Posted by Jim Andrada on June 01, 2002 at 01:55:07:
In Reply to: Re: Re: Re: Swedging Your Rotors posted by Chuck(G) on May 31, 2002 at 22:56:29:
Well, I'm not enough of a bearing engineer to really know the answer, but I remember talking to such an engineer once and asking why high-end electric scroll saws used plain sleeve bearings instead of roller or ball bearings and the answer was (in part) that ball bearings etc were really great for full rotary motion (ie things that spin) but poor for "rocking" motion because the balls wouldn't move around enough and would wear quickly.
I also remember some problems we had in the "old days" when disk drives were refrigerator size and we used lots of high - very high - priced ball bearings in the then high-end linear stroke actuator assemblies that carried the read/write heads.
One of our customers (I think it was GM Research Labs)had an application that caused the heads to hover over one or two tracks on the disk most of the day just wiggling imperceptibly and occasionally making a full stroke across the surface, and after a while we started getting errors on the full stroke. It turned out that the tight rocking motion was simply flexing the lubricant in the bearings without actually shearing it and this caused the lubricant to sort of "work harden" and get stiff, and resist shearing more strongly such that it interfered with full stroke timing.
All of which probably has nothing to do with tuba rotor bearings and the real answer may be totally related to tradition, but it could also suggest that there might be more to all this than meets the eye.
All standard disclaimers apply, Your mileage may vary. The above may be total nonsense.