Prop testing

By kwadkenstine on Dec 29, 2020

9  234  8

Hi all .
As the debate rages on about prop configureation and power gains/ losses.
I did some crude testing on my janky rig.
Each run was on a fresh charged 1300mah 4s.
I tested counter rotating and props spinning in the same direction.
Ramped them up to just over 50% t and then pulled it back to 50%, marked the grapf and read the amp draw.
The results were as i expected .
What did you think would have been the result.
I am not going to ainalise the rig or the results ,
Thats your job!!!



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Jodie Froster   Dec 31, 2020  

The results I would interprit from this data: the counter-rotating setup is less effecient AND less powerful.
There are a few things i'd like to see:
It's hard to trust that your paper was in the same place on both tests when the starting point for the marker is not the same. Maybe just a redo.
The chain is a good weight in that it doesn't swing, but a bad one in that it gets heavier every link you lift: maybe just one or two heavy objects in the middle of a cord, so part of it can still be attached to the ground, but it doesn't get so heavy that it overtaxes your setup and you can't reasonably take the throttle up very high. I'd like to see you test at a few different throttle points. In a perfect world i'd like to see 25%, 50%-80%, and a full throttle test. I can almost assure you that you will see different effeciencies and power values at these throttle values,
I would like to see the effect of higher blade count props, I wonder if counter-rotating does more or less to 3 or 4 prop setups?
I love that you set this up, and shared it with us!

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Kstone   Jan 10, 2021 

As strange as this may sound, one on my many Jobs while working for the Naval Laboratory was one of jet engine Test-Cell instrument certification. Its a huge version of what I just described for you for testing out rebuilt turbo-jets. (Clarification: The instrumentation not the engines)

Here is what testing looks like at a dedicated engine facility:

Example of Ship-Board testing:

For a team of 2-3 it would take about a week to test and calibrate the entire stand. Which consisted of Voltage, Current, RPM, Vibration, Temperature and wiring checks. Most of this would be testing the instrumentation from the control booth to the engine stand and then saving the calibration constants to a computer for later reference.

kwadkenstine   Jan 10, 2021 

You win , your test stand is bigger than my test

Kstone   Jan 10, 2021 

That wasn't the point... was trying to help you as after all this is the 2nd or 3rd build you've done to test this out. Besides, it's not about perfection as thats like chasing the dragon but instead finding a balance between what we desire and what we are currently capable of.

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