I have a motore with a propeller anchored to a load cell to measure the lift produced at varying power inputs. This is for a student activity I am running and I wanted to show that though more power in gives more lift there is a point after which efficiencey starts to go down again so I tried to also calculate the power output of the propellers to get the efficiency of the blades.(adsbygoogle = window.adsbygoogle || []).push({});

***Edit***:Thought of a better way of explaining this. if it was a fixed wing I would move it D distance in T time generating F force and my power would be F*D/T. but for a rotating blade the distance D it moves in T time depends how close to the end you are and I can't figure out how to calculate ecounting for that.

Any help would be great thanks.

***old thoughts***

I thought at first the propelor would effectively have potential energy as it applies a constant force like gravity does but the energey in goes up by time where the potential goes up by time squared.

I tried to calculate the speed it would have if not anchored by picking an arbitrary time and deviding by the mass however as you can see from the attachment that's wrong as it would accelerate for ever so the power out increases with time while the power in stays the same.

Any idea how I can work this?

Should my speed be the rotational speed of the propeller maybe? (or would that just give me the power output of the motor).

maybe I need to calculate the volumetric air flow from pressure (getting pressure from force and propeller area) and take speed from that.

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# Power output of an anchored propeller

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