DIY Dyno? I want to see the video after that roller seizes.
Why would the roller seize? Looking at the web pages, it appears to have all been properly thought out, engineered & mounted in hoofing great industrial bearings more than capable of dealing with the forces in play.
Far from being Darwinistic It’s guys with attitude like this that have & will be progressing mankind forward, without them we’d probably still be sitting around in caves wishing someone would invent a safety spear so we could go out & kill something without any risk of cutting ourselves! 
Well, I’ll let people like that find out for themselves. Anyway I don’t need a spear, I’ve got Sainsburys.
Look at that guy, progressing mankind forward 
Probably wouldn’t have happened if he’d built his own dyno & run it on that instead… 