Is there any good reason why a Chinook doesn't have blade fold? I would have thought that there are users who would have wanted the capability.
Ref the Mi-26, here is the main rotor hub and gearbox (thanks to Aviastar.org). Shame there is no-one next to the gearbox for scale:
It does seem strange that the biggest operational lifter is a single and not a twin rotor. Maybe the drive shafts to the other rotor just get too big? Evidently the Mi-12 wasn't a roaring success, and the Yak-60 with the same drivetrain as a tandem rotor didn't get off the drawing board. The latter would have been a sight to see though, with four times the lifting capacity of a Chinook.
Technical data for Yak-60 Rotor diameter: 35m, fuselage length: 46m, take-off weight: 100,000kg, empty weight: 55,000kg