I've really enjoyed Wintergatan on YouTube (you've perhaps seen the viral music video of a steampunk one man band powered by marbles). He is working on the third iteration of the marble machine, and his process is incredibly thorough.
Don't read the comments, half his fans seem to hate him now for turning an art channel into an engineering channel. But that's why I watch!
Interestingly, I didn't have the same experience from the comments, I find it rather good by YouTube standards.
When I followed the MMX saga, I saw a lot of technical criticism that ultimately turned out right. The most criticized idea I remember was about "kinetic fingers", a non-functional "art" part. The rest is mostly unsubstantial and vaguely entertaining comments that make up for the majority of what you see on YouTube comment sections.
Don't read the comments, half his fans seem to hate him now for turning an art channel into an engineering channel. But that's why I watch!
https://youtu.be/lC_oLb1pfqU