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When balancing a radially folding propeller, such as the MagCAD 60x23, what are some techniques to employ?

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A static balance is challenging because the orientation of the blades is not fixed.

Dynamic balancing might seem more natural, however vibration might also come from the way the blades pivot about their hinges as they swing through the propeller arc, similarly to a helicopter's lead-lag hinges.

And does it materially affect things if the blades are mounted horizontally or vertically? When they are mounted vertically, gravity will tend to advance the falling blade and retard the rising blade.

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    $\begingroup$ When those blades are spinning fast enough, it acts like a rigid propeller. I don't see the balancing procedure to be any different... $\endgroup$
    – Ron Beyer
    Sep 28, 2021 at 16:37
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    $\begingroup$ @mins, the prop in that video is an axially folding prop, so it cannot lead/lag. I don't know how that will affect vibration, maybe it doesn't at all? $\endgroup$ Sep 28, 2021 at 16:52
  • $\begingroup$ @RonBeyer I don't expect that it's true that they act like a rigid propeller. The blades should constantly be changing position as they sweep through their arc, in function of gravity and whether the blade is operating in clean air or not. This might not matter for balancing and vibration, though. $\endgroup$ Sep 28, 2021 at 16:54
  • $\begingroup$ Related, why lead/lag is rare on propellers per se: aviation.stackexchange.com/a/27356/31425 $\endgroup$ Sep 28, 2021 at 18:23

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The folding of the propellers closely resembles ... a weed trimmer!

Given sufficient rpm, the blades will point straight out, with any flexing from twisting or bending helping to hold them in place on the hub. Once the blades are spinning fast enough, the effects of gravity are negligible.

One may balance the hub/prop by carefully matching the two halves in shape and weight, then temporarily locking them in the extended position.

Standard balancing with a gradual run-up of rpm to specs could then be safely performed for quality control. Unmatching blades are discarded. The final, loose mounts are then installed and the prop/hub re-tested.

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