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TTools V2.0

7 April 2010, 19:48, by HUN_Lac

It’s a pretty good software!

To the mechanical part I have to admit, that as I could measure and experience it, LEGO gears and the whole driveshaft is very inefficient. I think, it’s impossible, to achieve such high efficiency rates as in real life, even with spur gears. IMO efficiency changes at high forces (torques), which causes varying efficiencies from gearing to gearing. So you can rather only estimate the overall efficiency.
For estimating "back" the driveshaft efficiency, e.g. you can calculate the wheel torque by measuring the force, which the truck can pull (on smooth surface, to avoid stalling). Knowing the RPM, you can calculate the "motor power" from RPM-Ncm function (P = 2PI*f*M, of course all in SI), knowing the wheel RPM and torque you can count the "wheel power". If you divide the 2 powers, you get the (almost) real efficiency. Its much worse :(.

About the motors:
The mechanical power, that Philo gave at the given RPM-s, are sg like an avarage power, it hardly can be a constant... The calculated diagrams are made according to Philo’s diagrams (about 1,5 year ago), but they are inaccurate. Note, that according to Philo, RC motors give 3,925W (on it’s outer output, at 9V) at 500RPM!
(P= 2*3,14*500/60*0,075=3,925)

Moreover, I have measured these characteristics as well, and they are a bit different from Philo’s (partly could be, because I measured the motor reaction force (=>torque)). In the summer I will make more measurements, then post you.

Some other: You might add lubrication, and an average "bearing" factor, which also influences efficiency;)

To sum it up, there are more inaccurate things here, but its much more than nothing;) So keep up the good work!