On 11/2/2017 1:38 PM, Leon Fisk wrote:
Affix something to the chain that sticks out a little. Now make another
attachment or hold something close by that will hit it. Like the old
clothespin, playing card and bicycle spokes. Turn it on and record the
sound. Use something like Audacity to measure the frequency. Viola!


I like it ... that's really clever! The only tricky part is affixing
something to the chain - there's not much clearance. I'd tack weld, or
solder, a bit of wire.