TL,DR: three blades (1) are a good balance of torque against drag at different speeds, (2) help reduce unbalanced forces compared to two-blade turbines, and (3) provide visual balance, smoother motion, and quieter operation to improve community acceptance.
That has to do with the physics of harmonic vibration.
It's not that you can't make even numbers of spokes balanced, it's just marginally easier to do odd numbers.
Back in ye-olden days when things sucked there were more manufacturing benefits to it too but these days (this century) that doesn't really matter because even the sloppiest casting factory in china has their stuff figured out.
There are companies working on two blade design, which has other benefits. You can try to get rid of balance problem with mechanical design and software:
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[ 2.9 ms ] story [ 26.9 ms ] threadIt's not that you can't make even numbers of spokes balanced, it's just marginally easier to do odd numbers.
Back in ye-olden days when things sucked there were more manufacturing benefits to it too but these days (this century) that doesn't really matter because even the sloppiest casting factory in china has their stuff figured out.
PSA: the si, as well as pp, parameter is used for tracking.
If possible consider trimming them when copy-pasting.
https://youtu.be/GbeFYLI8zYg?si=32wECCs05c4rRfs6
I was recalling the article as I was driving and -- surprise -- a two-bladed one appeared suddenly (two, actually).
This was the only time I saw two bladed wind turbines and could makr intelligent comments about why 3 and not 1 or 2 :)
So thank you!