[R-390] Another geartrain tidbit

[Barry]

While cleaning and reassembling one of the split gears tonight, I discovered
something interesting.  No matter how much I wetsanded the faces of the
teeth, when I reassembled the halves the assembly would bind and the two
halves would not move freely against each other.  I had this happen (to a
lesser degree) on another gear set and I was determined to figure out why on
this one.

It turned out that the half of the gear that has the hub brazed onto it had
a slightly convex shape.  When I pushed the snap ring down into its groove,
it was applying pressure on the flat gear forcing it against the non-flat
half and only the outer edges near the teeth were pressing together.  Laying
a straight edge against the side of the gear confirmed this.  It was about
0.015" to 0.020" out of flat.

I was able to use a steel disk (with a hole in it just a little smaller than
the OD of the gear and a neoprene hammer to flatten the outer gear.  Well,
actually, the gear material was a lot softer than I anticipated and I ended
up getting it convex in the other direction; however a few taps with another
setup and I was able to get it flat again.

Now the two halves rotate quite freely against each other with the snap ring
in place and the antibacklash springs are easily set to a tooth or two of
tension.

Just thought I'd pass this along.  It wasn't easy to see the problem with
this one.

Barry(III) - N4BUQ