02-12-2011, 02:48 PM
Here's another thrust calculation I thought of this morning ...
Power = Force * velocity (http://en.wikipedia.org/wiki/Power_(physics))
so Force = Power/velocity
The "Force" is the thrust, obviously. We get a power reading from a Wattmeter in a static test and remove about 15% of the reading because most brushless motors are roughly 85% efficient. Then estimate the velocity using the propeller/fan pitch and rpm (or measure the efflux speed in a static test if you have an anemometer) and there you go, a thrust estimate.
Power = Force * velocity (http://en.wikipedia.org/wiki/Power_(physics))
so Force = Power/velocity
The "Force" is the thrust, obviously. We get a power reading from a Wattmeter in a static test and remove about 15% of the reading because most brushless motors are roughly 85% efficient. Then estimate the velocity using the propeller/fan pitch and rpm (or measure the efflux speed in a static test if you have an anemometer) and there you go, a thrust estimate.
Steve Murray