Originally Posted by
chucky
This study reports a 5% increase in efficiency for bigger cogs and a 2% decrease from standard cluster to IGH with small cogs:
http://www.ihpva.org/HParchive/PDF/hp52-2001.pdf
So if you combine the two the net increase is ~3% for a properly configured hub gear.
Other studies have reported similar results.
You might feel differently if it were easier to shift between widely dispersed gears (it doesn't necessarily have to be THE lowest and THE highest gear...just as easy to use 2 and 7 or 3 and 6 or whatever tickles your fancy...once you get good with the shifter you just slap it and it magically goes to the gear you want). Personally if I were going to be starting in less than ideal gears I'd sooner take a singlespeed bike than a derailleur (why bother having them if you can't use them to the fullest?). To each his own.
But I agree that it's not
that hard to get into the right gear with a derailleur before stopping...it's just that I'd rather be focusing on braking, filtering, whether I can beat the yellow, picking my nose, etc because it's safer to reduce multitasking when possible. I also often change my mind about what gear I'm going to start with once I'm done picking my nose and have time to inspect the condition of the intersection (amount of potholes, etc) or if I decide to take a shortcut (right on red, maybe move to left lane for an upcoming turn...or maybe even run the light if no cross traffic).
Yeah, well there's no substitute for trying it yourself. Sheldon knew that very well: Some of the stuff he did should make anyone cringe, but there's no arguing with success.
As to the lubrication (if we'll ever let it die), some of the engineering requirements also relate to cleanliness. If we listened to them we'd have to conclude that roller chain is unsuitable for exposed bicycle use.
Let us know. The one I'm building is 44/22 (not enough clearance for 46/23 or 48/24), but this one's a recumbent so the carbon frame will probably delaminate before the chain even begins to show signs of wear.
If you have hung around here around here long enough you would see that when it comes to setting up singular drives I always advise using the largest chain rings and cogs that are practical as it has been known for a long time that smaller cogs decrease efficiency and drive train efficiency drops off markedly when you use a cog smaller than 13 teeth.
A singular drive with a clean chain and proper chain alignment will lose about 1% and this is what makes a fixed gear bike the most efficient bicycle from a mechanical standpoint but not as efficient from a practical standpoint as humans have such a narrow power band.
We have to include the engine in all of this...
Across a multiple speed cassette the frictional losses will vary widely and you may only lose 1% when you are running in those positions where your chain is straight and cog sizes are reasonable and will lose more when you are using the cogs with less than 13 teeth.
Losses approaching 20 % can be observed when you cross chain the drive depending on which way you are cross chaining.
If used correctly a derailleur equipped bike can also be extremely efficient as it allows riders to match their output to the conditions and a wider gear range more than offsets minor efficiency losses and if you can shift effectively efficiency loss can be kept to a minimum.
With an IGH you run the same straight chainline and because the drive gears are sealed the mechanical losses should remain consistent within the hub and are quite low... with any hub gear the direct drive is the most efficient as there are no moving parts and it runs like the fixed gear bicycle. Move away from the direct drive position and the efficiency will drop a little.
Modern hub gears are getting better and better and if the Shimano 11 speed proves to be successful it will come very close to offering the range and smaller steps you get out of a derailleur equipped bicycle at an affordable price and he price of the Nuvinci has come down a fair bit.
Most people's complaint about 8 speeds is that the steps between gears are too large and that you sacrifice top end for a lower gear or bottom end for a better top gear... this also is a factor in overall efficiency.