gbritnell's engine is most definitely wonderful. There's no escaping that. But the vast majority of engines here are IC, steam or related (sadly, including my own when I can get started) so are covering known ground.
Bogs' engines both enter territory not that often covered and are examples of a degree and kind of precision not commonly found here. His style makes it look and sound simple because, in the end, it is simple. He is paving a new road for us and showing it's not only possible in the common hobbiest shop but can be fun as well. Later spindles will require finer balance to achieve higher speeds without shaking themselves to death and playing with the blade profiles to gain even more power but the basics are there.
Because of the route he took, I voted for Bogs' triple spindle engine and would love to add at least 19 more votes for it ("America's Got Talent" reference) and look forward to anyone picking up this concept and advancing it.
Best regards,
Kludge