Originally Posted by
Kimmo
very likely to be more efficient than a pristine derailer drivetrain.
How do you figure? The drawings show two chains inside the gearbox (pedals -> first cassette, then first cassette-> second cassette) then you have the chain/belt to the rear wheel. So there are three separate chains and four axes spinning all under load. Plus some sort of derailleur/tensioner for the chain between the two cassettes. A derailleur drivetrain only has one chain and two loaded axes.
Your point about cleanliness is well taken, but that's more the purview of gravel and MTB riding. Road drivetrains remain quite clean for a long time.
I hope to see more of this gearbox, but let's be honest about the challenges it faces and efficiency is likely one of them when compared to a road bike that is given reasonable maintenance. Based on the form factor of this, it looks to me like part of the motivation is to commonize frames for bicycles and electric mopeds