Originally Posted by
tiger1964
Sounds like you've thought this through. Tell me why I should not worry about rotational "friction" being transmitted from 4534/4535 to 3674 to 3670 to 4413, thus unscrewing 3673. I don't think you're missing something -- I am.
If you look at 3670 in the diagram, it has the flat sided hole so it can't rotate on the flat sided braze on boss. If it can't rotate, it can't turn the screw head.
Of course, all friction shifters have a washer like that, but those shifters are constantly wiggling them back and forth. The Simplex shifter only ever tries to turn in a single direction, so no wiggling.