I've used the tachometer to make a MOI meter as well. It is basicly a pendulum that can be clamped onto any shelf and the meter gives you the oscilations per minute (RPM) of that pendulum. In this case I found putting some reflective tape on the shaft improves stability and accuracy. As with the frequency meter small oscillations give a very stable readout, so the club being "caught" between the 2 suspention bars that hold the cradle in place is no problem.
The MOI can be calculated from the readout of the meter (in RPM), Swing Weight (SW in gram-inch) and total weight (m in gram) of the club :
MOI = 35.21 (SW + 14m) / RPM² (in kg-inch²)
and in action :
Print files are here : https://www.thingiverse.com/thing:5738540
