Hi All,

Here's a video I did on optimal gear switching ratios for PF motors. A formula presented relating the power operating point as a percentage of peak power. From this an operational power range band is defined based on maintaining a power efficiency of at least E percent. From this, optimal switching points relative to the motor torque are derived and the correct gear switching ratio determined. These are presented as formulas and graphs. The peak torque and power points are shown for Lego technic PF medium motors, Lego Techinc PF Large Motors and Lego Technic PF XL Motors.

 

Very interesting video! Knowing these ratios will be very helpful when designing gearboxes. One thing thing to note, I think you implied this, is that having a specific ratio between gears only optimizes the efficiency when the final gear ratio is chosen so that the motor is operating close to its peak power.