# I am confused on how to measure thrust for a propeller and would like some help

For my science project, I am measuring the power and efficiency of different propellers. I was researching thrust stands and that seems to be the best way to measure thrust. I already have a brushless motor, esc, battery, transmitter, and receiver. I was wondering what would be the best thrust stand for my uses (the propellers are about 6 to 8 inches). I also would like to measure efficiency and I am not sure how to do that. Would I use a watt meter?

Thanks

Edit: I also am confused on which unit to measure efficiency in. Should I use watt per grams of thrust or volts per gram?

Yes, you'd use a watt meter. It's possible to measure volts and amps separately and multiply them together to get watts, but it's convenient to have a device that does it automatically. Additionally most cheap multi-meters only measure up to 10amps, and motors commonly use a lot more.

'Efficiency' has several definitions, especially as a static motor is technically wasting all its power blowing air around and not going anywhere!

Watts per gram of thrust is probably the simplest to measure, although it is just a static measurement and doesn't tell you anything about how the prop will work once it's moving.

To really measure efficiency you'd need to measure the speed of the air leaving the prop and work out how much power the prop is transferring to the moving air. You could use a pitot tube and manometer for this, or an electronic wind gauge. Given the diameter of the prop disk and the speed, you can work out the volume of air going through the prop every second. You can look up the density of air to get the mass. The mass and speed give you the kinetic energy transferred every second, which is the power output.