Originally Posted by
Happy Feet
...
Off the top though, if we use the 1.9 ratio as a limit, what would the best combination be to allow the climbing of steep hills fully loaded while still not over stressing the hub? What would one choose for the Rohloff? I am admittedly, not a gearing expert.
I think Sturmey Archer instructions should be used, if any.
My Dual Drive, if I recall the only constraint from Sram was that it should not be used on cargo bikes, but your Sturmey Archer link said the Sturmey Archer was designed for heavy duty use.
The Rohloff has a third planetary gear that acts as a low range, so the Rohloff can put a lot of torque onto the non-drive side of the frame. Sturmey Archer can't put that much stress on the frame because the gear range is much smaller. If you took that Sturmey Archer five speed and added a low range to it so that it was a 10 speed, and the lowest 5 speeds were in the low range and your existing 5 speeds would be the high range, that is basically what Rohloff did. The Rohloff is 14 speeds, gear 11 is direct drive.
I would think that a 30T chainring and 20T sprocket like I used in the calculator would work ok, but I still think it would be a good idea to verify with Sturmey Archer that it would not over stress the hub.