Neil Ungar had a great idea. He welded a section of square tubing on a plate
and filled the empty volume with liquid  polyurethane. Polyurethane is a very
tough flexible plastic used in race car suspension bushings.

I incorporated it into a 1.5 inch diameter hollow gear box input shaft.
Now one piece.

The aluminum spacer Neil used is made longer and a star shaped cavity is
NC milled into it. Since you MUST use six metric screws to bolt to
the counter weight a star instead of a square shape can be larger in diameter reducing
the stress on the Polyurethane. The input shaft is made from a bar of
steel machined on a lathe and then the small star is NC milled
on it.

Most input shafts are one inch in diameter. The advantage of the
1.5 diameter shaft is it is easier to assemble the large  gear box adapter plate and
the sun gear fixing to the shaft is much, much stronger. Dave Leonard had
trouble with the sun gear pins shearing off. This uses 10 extended point set
screws instead which Chris Hoskins is using.

Of course all this is hindsight based on 17 years of the news letter.
If it can be failed some one on here will fail it :-)

Paul Lamar