[AceJohnny2]

I highly recommend that user's full channel:

https://www.youtube.com/user/akiyuky/videos

Akiyuky is apparently a process engineer in Japan, and posts impressive lego-based contraptions.

A lot of of them are for GBC, or "Great Ball Contraption", a collaborative project to make lego modules whose sole purpose is to move standard lego balls from one point to another. You'll often see collections of these at lego conventions. For example:

https://www.youtube.com/watch?v=_cbpNV8ivME

[swaggyBoatswain]

Related, checkout matthias wendel who does woodwork and lego contraptions

Lego domino row building machine

https://www.youtube.com/watch?v=de4xdOVVROQ

Also, for other mechanical motions I really like watching thang

https://www.youtube.com/user/thang010146/videos

[bscphil]

That Matthias video takes me back - one of the first channels I ever subscribed to back in 2007 because of this cool wooden marble adding machine: https://www.youtube.com/watch?v=GcDshWmhF4A

[jypepin]

Thanks for sharing, this last video about GBC is just mesmerising!