On Mon, 29 Oct 2007 01:02:04 GMT,
(Tom) wrote:


Hey, these look good for a project I have in mind. Do they have lower
low-speed starting and rolling resistance than lesser bearings? The
project is a little cup-type aenomometer. I got the hemispherical
cups last week.
You may get just the opposite effect. Because the tolerances are held
so closely you may have less internal clearance (unless you specify
more). Best bet is to consider the lubricant and use a minimal amount
of very lightweight oil.

The internal clearance on deep groove bearings is specified
independently of the the precision class. As far as I know, the
standard clearance is more or less the same across all classes.

Lubricant _is_ a very big factor if the goal is to minimize friction
at low loads. I kludged a simple test rig to measure bearing drag for
a project that required very low drag at high speeds. It consisted of
a piece of fine spring wire held in the Bridgeport spindle which drove
the outer race of the bearing. A strobe illuminated a circular paper
scale graduated to indicate the deflection of the spring with the
spindle turning. It was easy to see the effect of lubicant viscosity
with this setup.

I thought I had a photo, but all I can find is the final product.
http://www.suscom-maine.net/~nsimmons/news/P8260002.JPG
http://www.suscom-maine.net/~nsimmons/news/P8260001.JPG

The geometry of deep groove bearings guarantees there'll always be
some sliding between the balls and race, so they're not ideal where
friction must be minimized.

--
Ned Simmons