How do I calculate the thrust of a motor ?

I know the volts, watts and amps, but is it enough to calculate thrust ?

Unfortunately it's the prop that creates thrust not the motor so none of those are any real use. What you need is the prop size and speed (rpm). Or use one of the motor calculators which will give you a reasonable idea.

Steve

why would you want to anyway?

Doing a google search for "rc thrust calculator" will probably prove to you that thrust calculators are not very practical or accurate. There is just too many variable involved.

I think thrust is best measured, not calculated. And measuring it in a static situation, while useful, does not tell you how much thrust will be delivered in flight.

But I've found it useful or entertaining to know how much thrust a given motor and prop combo is delivering to the airframe.

I do it with a 10 kilogram hanging scale as seen in the photos. The scale is tared out to clear the plane's weight, the motor is run up, and then I see the peak thrust that was obtained in the test. That is close enough for me.

For bigger planes I can set the plane on the ground and use the scale on a simple vertical stand with a turning block. The stand is weighted/fastened down, the plane is attached to the scale, and the pulling forces measured.

The scale was found on eBay for about $10 shipped.

Jack

https://www.rcgroups.com/forums/show...t=thrust+stand

There are a few sources around that already know how much thrust a particular prop generates at a specific RPM.
I'm at a loss right now tho...

http://www.badcock.net/cgi-bin/powertrain/propconst.cgi

According to my limited testing with various props and EDFs, 115w/ lb thrust for props and 335W/lb for EDFs is a reasonable starting point, with EDFs being more consistent than props. As others have said, the only real way to know is to measure that prop and that motor on a test rig. These starting values assume you are using recommended motor/prop/EDF combos.