Browsing your topic list I came across your overhead beam trolley and electric hoist solution (second video).
What made me curious is your fitness contra weights to compensate the motor to keep balance.
But is that not extra weight that your beam and wood will have to carry?

I have bought this electric hoist for lifting my Lathe&Mill combi around 250Kg after strenghten the drawer table with pipes.
When mounting the electric hoist parallel with the overhead beam it will be in balance by itself. (See picture on the right.)
Click image for larger version. 

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I have to design the trolley yet and find your duo u-profiles idea promising.
Wouldn't a construction like this ] █ [ where the middle is a rectangle tube, be easier to weld and stronger?
With welds 20cm apart on the top and bottom would be enough?
Which ] [ profiles dimensions did you use?