[R-390] R390/URR Gear train

[David Wise]

When I got my R-390A, I worked over the gear train.  One notable thing I discovered was that one or more split gears were wrong way around.  More effort is required to raise a rack than to lower it, and the fixed gear should push in the high-effort direction and the springy gear in the low-effort direction.  This lets you use minimal preload, which reduces friction.  It's complicated by the way effort adds up from all the downstream racks, and sometimes you are raising a rack on the steep backside slope of its cam.  Taking all that into account, I reversed a gear or two.  Sorry, I didn't take notes.

Dave Wise