Say I have a place where apples are transferred from singular cups to
wieght cups and the timing must be perfect.

The chain between the two makes a U around an idler sprocket. This
sprocket can be quickly rasied/lowered with a threaded bolt and
handweel, changing the length of chain between the singulator and
weight cup conveyors and thus the timing. Quick and accurate to change
while the machine runs.

may not fit your application, but one clever idea.

Karl