Nonsliding Roller Bearing

This is a roller bearing that can be printed in one piece.

**edit:** needs improvement; see below.

The special thing about it:
It has less sliding friction than a roller bearing *with* cage.
This is archived through the central rolls.
Those let the inner and outer rolls roll on rolls.
This bearing can can take radial and axial force.

It should run under (axial) load so that rolling is ensured !
A preload would work to but than a zero clearnce print with post assembly is required.
(split the ring or better the center piece in two for that)

A little bit of unavoidable friction occurs at the slanted top & bottom retainers but this should'nt hurt.
(gears also have a tiny friction component)

It was inspired by this thing:
http://www.thingiverse.com/thing:55515
Which in turn was inspired by emmets popular gear bearing.
http://www.thingiverse.com/thing:53451

**This needs improvement !**
My test-print fused together on the outer e