4th Axis Precision Testing - 50:1 Harmonic Drive from Aliexpress
This is the GPenny 50:1 Harmonic Drive 4th axis, purchased from Aliexpress: https://s.click.aliexpress.com/e/_AKqJgn (Affiliate link)
Just some quick tests to give an idea of backlash and play in the system, and some calculations from Deime on the PrintNC Discord. 30mm spanner mass = 516g:
.01mm of movement, 50mm from the center is .011 degrees
That's also the deflection when it's subjected to 1.5Nm of torque. So rotational complaince is .0076 deg/Nm, stiffness 130.9Nm/deg