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The above graph (minus annotations) was produced with the following link
here
1) Vertical labels indicate the current the noted prop would draw at the given voltage.
Note the diamond is drawn on the blue efficiency curve, but they could have been
correctly placed on any of the curves since the diamond indicates the current draw
that prop will draw on the noted motor at the noted voltage. In this case, putting
a Graupner Miniprop 4.3x2.0 motor on a HiMaxx HA2025-4200 motor and powering it
from a 10V supply will result in the motor consuming just over 18A, the prop producing
962g of static thrust at a pitch speed of 69 MPH. Prop data used in the graph is
measured data imported from the excellent work done in Drive Calculator.
If the prop label is in black, then the prop RPM is estimated safe. If the prop
label is gold/yellow, then the prop might be operating at an unsafe RPM and you
should consult the manufacturer's specifications on that prop. If if the prop label
is red, then the prop RPM is exceeding the manufacturer's RPM recommendation.
2) Reading motor efficiency is done by noting intersection of current and the blue
efficiency curve. With the 4.3x2 prop, efficiency is about 83%. Note that ESCs and
batteries and the the prop are not factored in here. This is simply the Pout/Pin
of the motor, which is a measure of how good the motor is at converting electrical
energy into mechanical energy.
3) Noting where the green line intersects the operating current will yield the power
input to the motor. With the 4.3x2 prop, it's about 185W of point going into
the motor.
4) Noting where the gold line intersects the operating current will yield the RPM
for the prop. In the case of the 4.3x2 prop, it'll consume just over 18A at 10V
on this motor, and turn about 36K RPM at that voltage.
5) Thermal power is a measure of how much power is converted into heat. The closer
you operate to peak efficiency of a motor, the harder you'll be able to push the
motor because less of the power is being converted into heat. Currently, the motor
weight is used to determine how much heat the motor can dissipate and for how long
it can dissipate it. Ideally we should be characterizing various motor cases to
determine Theta for case-to-ambient. T = Ta+
Pd * Thetaca.
For now, the closer you operate to the red region, the hotter the motor will get.
Inside the red region may damage the motor. I really depends on an enormous number
of variables.
6) These labels note the parameters used to generate the graph.
7) A text summary of the red region of the graph.
8) The peak in the blue curve represents the peak efficiency of the motor.Generally
motors will operate to the right of that peak for most of the flight.
9) The title idicates the manufacturer, model of motor, and the voltage.
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