And that's why innovators keep trying to come up with new and better alternatives.
The latest is a shaft drive transmission from Ceramicspeed - the same people who have been pushing the envelope with pricey lubricants, bearings and derailleur pulleys to eliminate drivetrain friction - in a quest to get drivetrain efficiency up to 99%. Their new shaft system uses carbon fiber, tiny ceramic bearings, and raspy-looking cogs with rows of outward-pointing teeth.
|Though the pictures show a multispeed (I count 13) cog set, it's apparently only a mock-up as they haven't actually figured out exactly how to get the system to shift across all those teeth.|
|Instead of bevel gears, as most shaft drive systems employ, the Ceramicspeed design uses a pinion with tiny rollers to engage the outward-pointing teeth on the cogs. It's supposed to virtually eliminate friction.|
|. . . And it apparently works - as long as you don't want to shift gears. . . yet.|
Some caveats. First - the system is still very early in its development and there are a lot of issues that remain to be solved. One major issue (mentioned already) is that so far it cannot shift gears. There are some ideas involving a small electric motor to move the roller-bearing pinion forward or backward along the face of those cogs - but how to get it to move across those teeth in a synchronized way at speed and under load is something of a puzzle. Imagine shifting gears in a manual transmission car without use of the clutch, and without (or with worn out) gear synchros. Caarrunch!
Second - there is no compatibility, and likely no way to make it compatible with any existing bikes or frames. That shouldn't be a surprise, since it's a totally new thing, but bikes would definitely need to be built specifically for it. And I cannot even imagine what it would do to wheel changes.
Another thing to consider is the complexity and cost. I simply cannot foresee any way that a system like this could even approach the cost of chains and "normal" cogs. That raspy-looking cog set bears an unlikely combination of looking simultaneously fragile and dangerous, in addition to probably being a real bear to make.
A couple things to remember - shaft drive is nothing new. Columbia Bicycles (Pope Bicycle Mfg.) had a shaft drive bike as early as the 1890s. I don't believe they were the only ones, either. This was before the roller chain we've known for about a century took its current form and established itself as the preferred transmission. In a manner of speaking, one could argue that the chain was the improvement over the shaft. The shaft was overly complex, less efficient, and too expensive to manufacture as compared to chains. But that hasn't stopped numerous companies and "innovators" from trying to re-invent them.
|Turn of the century (the 20th century, that is) Columbia shaft drive bike. It would appear that the bike had rear suspension, too.|
|Modern shaft drive from Dynamic in the UK.|
So, is there a shaft-drive bicycle in your future? Meh. Probably not.