Originally Posted by
tiger1964
Thanks -- whichever question you were answering.
A while back I found and copied this from the internet somewhere: "
The internal planetary gear hubs measured were the Shimano Alfine 11, Rohloff 500/14 Speedhub, SRAM Dual-Drive, and the Sturmey Archer X-RK8(W). In addition a single-speed direct chain drive, a single-speed belt drive, and a 7-speed derailleur system were measured. The efficiency of the Shimano Alfine ranged from 90.4% to 96.6%. The efficiency of the Rohloff speed hub ranged from 95.8% to 99.5%. The efficiency of the Sturmey Archer hub ranged from 84.6% to 99.8%. The efficiency of the single speed chain drive was found to be 99.71% and the belt drive 98.0%. The efficiency of the 7-speed derailleur ranged from 97.7% to 99.4%. These values found for efficiency are comparable to other studies." That 84.6% on the S-A hub scares me a bit, unless it's on a granny gear I'll rarely use... that's what I am trying to find out... how to get a reasonable range of gears, and specifically minimize losses in the "sweet spot" of gearing where I spend most of my time.
My 'No' is that there is not a fundamental flaw in your plan
The only exception IME/IMO is 'unless you get an Alfine 11-speed' which IMO is a poorly designed hub. I also found that Shimano would not support its being fixed when it developed problems, which seems very likely.
The efficiency thing IME isn't a worry. If you go with a vintage Sturmey Archer you'll find them as free in any gear as the best Campagnolo hub made. The efficiency drops with more and more gears, but I can tell you that in the case of the Rohloff, which arguably is the ultimate IGH and is also the least efficient, that two variables exist that don't get the attention they should and apply to any IGH.
The first is the IGHs take a bit of break-in. The Rohloff needs about 700 miles to really free up IME. They are never measured after break-in; apparently only right out of the box. The second is that if there is any dirt or the like to mess with your derailleur system its efficiency drops to below that of the Rohloff's measured numbers. So to really have the numbers you quoted be a thing, you have to really be on top of your maintenance. One gummy jockey wheel or slightly gummed up chain can mess with it enough that even a Rohloff is more efficient.
My only other advice is research your IGH prior to purchase. If getting an 8-speed my choice would be the Shimano Alfine (its as good as the 11-speed is bad if that make any sense).
Any IGH can be shifted without loosing cadence. You have to practice a bit but the trick is to shift when one of your feet is at 12 o'clock in its stroke- IOW when its torque is least. The amount of time you spend servicing things is reduced and its nice to shift quickly at any speed including a dead stop. IME the British SA hubs are designed to shift while peddling. This is particularly true of the 4 and 5 speed hubs.