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]Here[/url] is the Nicolai one.
You can see it is part of the frame and they use the gboxx idea.
The ground clearance argument about a BB based gearbox is boloney - your BB clearance is not defined by the diameter of the BB shell, it's the diameter of your largest chainring. So long as the BB shell is no larger than whatever chainring you'd chose to drive a hub mounted g-box then it makes no difference, and more significantly makes the weight of the drivetrain unsprung (assuming a the BB shell isn't rigidly attached to the stays)
With a constant chainline you have more ability to control the suspension behaviour under load as the point of force will always be the same and therefore could be compensated for.
Not sure I like the idea of including the freewheel mechanism into the BB shell, as that would mean that when freewheeling down hill it'd be like straddling a chainsaw!
how is putting a geared hub where the BB is, instead of at the back, any heavier at all?
youve just moved it forward, which can only be a good thing anyway?
how is putting a geared hub where the BB is, instead of at the back, any heavier at all?
cos the bb shell is integral to the frame making it bigger is heavier than just a big hub
anyway, the answer is no - they have not had their day, but they are moving into middle age.
Padowan, but if you had something the size of a G-Boxx, for arguments' sake, but centred on the BB, you'd lose any ground clearance advantages?
If you were comparing a standard BB with no chainrings, to a G-Boxx with the input drive at the same point (BB) then yes, the G-Boxx would reduce your ground clearance (between ground and "BB" shell) because it's taking the drive that goes to the hub upwards meaning that the drive sprocket (however big it is) shouldn't protrude below the BB shell.
But I was looking at it from the point of having something like a Alfine or Rolhoff where the input and output shafts are on the same axis, where the drive gears surround the input shaft (BB) and drive a chainring around the same rotational point. In that instance, for a given chainring that becomes your clearance limitation over a hub mounted gearing.
An Alfine can only give you the range you'd get from one of your chainrings on a derailleured setup. How's that going to work for moderately fit somewhat overweight biffers like me somewhere with some steepish ups like the Qs?
Not really true about the Alfine, as you get a lot more gear spread than just one front chainring (on normal setup).
There are a few compromises, in terms of jumps between gears, but the Alfine will cover enough ratio's for most situations.
I'm a biffer too, and the Alfine is great IMHO
My understanding is the alfine is a bit more than a 1x9 but not as much as a 3x9 in terms of gear spread - sort of equivalent to a 11-38 rear casseette