Isaac is right, a string, weight, spool, and stop watch are the best method for this kind of measurement when speeds are low; e.g., when it takes several seconds for the weight to drop.
On the original topic, I recommend
this lugnut remover as cheap example of cycloidal gearing. It was easy to find at Harbor Freight years ago. Don't know if you can find it there now. I posted some details and pictures a few years back, linked earlier in this thread.
__________________
Richard Wallace
Mentor since 2011 for FRC 3620 Average Joes (St. Joseph, Michigan)
Mentor 2002-10 for FRC 931 Perpetual Chaos (St. Louis, Missouri)
since 2003
I believe in intuition and inspiration. Imagination is more important than knowledge. For knowledge is limited, whereas imagination embraces the entire world, stimulating progress, giving birth to evolution. It is, strictly speaking, a real factor in scientific research.
(Cosmic Religion : With Other Opinions and Aphorisms (1931) by Albert Einstein, p. 97)