Take Up Reel Adjustment/Sound drum tension...

[Jesse Crooks]

Probably too late to join in but...

Lots of projectionists in my country back then had a habit of placing their free hand on the takeup reel spoke, and give it a "push start" when first start the projector to help the reel to get up to the speed. Sounds crude/barbaric, but when properly done - it simply works.

While it doesn't fix the problem, I second this suggestion. If you're having trouble adjusting the clutch tension and can't get it just right, set it a little low and give the reel an assist as it starts. Before you start the motor, put just enough pressure on the reel to keep the film taught, and as the motor starts give it a little spin. It should catch up pretty quickly.