Plasma Attempt #2

[Jonathan]

Forgot to say, 0.0022kgm^2 will add about 0.45Nm to the stepper torque requirement - angular acceleration of shaft is 4*pig/0.6. So torque=4*pig/0.6*0.0022=0.45Nm. So there goes your 2* factor of safety!

If instead of the tube you used 12mm steel bar it's only 0.0082Nm added, which is about the same torque as a 24T HTD pulley will require. Critical speed of 12mm bar is fine, but to avoid needless vibration you could pop a bearing in the centre to support it.

Those powers of 4 really do give some surprising results.