Tetrix DC Drive Motor W739083 dynamometer data

[Richard Wallace]

Some folks here on CD have asked for a bit more data, so I am adding it here.

We used another of our dynamometers to measure mechanical output and efficiency for two of the Textric DC Drive motors (units 2 and 3 from the original post), with their gearheads removed. This gives some insight to the electrical and mechanical power losses.

At 12V dc, these two motors developed peak shaft powers ~ 17.6 and 15.8 Watts, respectively -- this is about 7 Watts more than was measured when the motors were tested with gearheads. That difference is the mechanical power loss in the gearhead, at peak loading.

Also, at peak shaft powers these two motors showed electromechanical efficiencies ~ 45% and 40%, respectively. In other words, motor 2 consumed 17.6 / 0.45 = 39 Watts, and motor 3 consumed 15.8 / 0.4 = 39.5 Watts, from the 12V dc supply. So motor 2 wasted 39 - 17.6 = 21.4 Watts, and motor 3 wasted 39.5 - 15.8 = 23.7 Watts, due to heating of their respective armature windings. These are the motors' electrical losses.

My conclusion -- teams might gain an advantage in climbing power by replacing the gearheads on these motors with more mechanically efficient alternatives, but the potential benefit is probably only a few Watts (my guess is 2 to 4 Watts). The time a team would spend refitting Tetrix motors with more efficient gearheads is probably better spent working on faster minibot deployment methods.