These are some ball bearings taken from computer fans. Really, the
term "ball bearing" is very misleading; it's much more accurate to call
these "bearing assemblies", since each donut shaped unit has a number
of round BB's sealed inside.
A "dual ball bearing fan" is a fan with two of these bearing assemblies supporting the fan shaft; a "single ball bearing fan" has one assembly.
Q. My fan says "ball bearing" on the label. Is that a single or
double ball bearing?
A. It depends on the company, but it typically means a single ball bearing.
Q. My fan says "one ball, one sleeve bearing"; what does that
A. With most computer fans, "one ball, one sleeve" is just another name for a single ball bearing fan. Here's what it looks like on the inside:
|Peeling up the hub label reveals the fan shaft and the lock-washer that holds it in place. Removing the lock washer allows the impeller to be removed from the other side:|
|With the impeller removed, the hub bearing can now be seen clearly. In this case, it's a sleeve bearing. You can tell just by the color. Sleeve bearings are made of an alloy, and have a bronze or copper color.|
|Turn the fan frame around so
you're looking at the stator, and you can see the other bearing. This
is the ball bearing.