Propeller Speed Calculator
Thank you to Marc Hoffmann for coming up with this. You can use this propeller speed calculator to estimate the rotational speed of your prop. Use this to get the most efficient propeller options on your motor. This calculator will help estimate the theoretical limits of your propeller on your selected motor and battery setup.
The drag of the air on the propeller will cause friction, and a loss in rotational speed. This calculator doesn’t take drag in to consideration. So if two props are close to the optimum speed, but one is slightly over, you may still want to test both.
Your motor will have a limit to the number of amps it can handle. Going over this limit will likely melt your motor. Ask me how I know 😜. So while this calculator will give a good idea of the speed of the propeller; it is your responsibility to make sure that the motor can handle the current the prop will pull.
This calculator will not let you know how fast your model will go. It calculates the theoretical maximum speed of your propeller, based on the prop pitch. It doesn’t know the drag profile or weight of your model.
The propeller speed calculator
The most convenient result to check on the propeller speed calculator is the metres per second (m/s) tip speed. This is colour coded to give an immediate idea of the potential performance of that prop with the selected motor KV and battery voltage.
Red indicates an inefficient choice. The propeller tips are moving too fast, which causes shock waves at the tips and the air detaching from the blades. This is above Mach 0.92.
Green indicates a good choice if you are looking to fly fast. The prop is on the red-line, close to the maximum speed it can handle, before losing efficiency. This is between Mach 0.88 and 0.92.
Blue indicates a good choice for endurance, efficiency, and quietness. The prop is operating in a window below Mach 0.62, which will not over stress the motor.
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