Carl Fogel wrote:

Ryan Cousineau wrote in message ...

[massive snip]

That's just the trick. Chain is so good, it defeats all other options.
You use belts or enclosures if the filth bothers you, but that's it.
Maybe some recumbents would benefit from a long, stiff shaft drive,
given their ludicrous chain issues.

Dear Ryan,

I love ludicrous issues.

I occasionally see recumbents wobbling along on
my local bicycle path, but have never inspected
a dead one's anatomy--possibly there is a secret
recumbent graveyard.

Recumbent owners keep their bikes forever.

There are no low quality/low price recumbents (equivalent to discount
store bikes) and the majority of commercially produced recumbents were
made in the last 10 years. Therefore, unlike upright bicycles, one is
unlikely to find recumbents in dumpsters, along the curb, at police
auctions of abandoned bikes, etc.

Is the length of the chain-run a problem? That is,
are longer chains less efficient, harder to shift,
more prone to wear?

Chain wear mainly occurs when the tension (power) side of the chain is
bent around the drive cog(s). Since recumbent chains are generally much
longer, they typically last much longer (assuming similar conditions of
use). I suspect that the cost per unit distance for recumbent chains
does not differ significantly from upright chains.

Shifting quality on a recumbent depends primarily on the quality of
derailleurs, shifters, cassettes and chainrings used. An advantage of
RWD recumbents is that the chain angle is lessened when the driven cog
does not line up with the driving chainring. One can get away with using
cross-gears much more so than on an upright. On the downside, recumbent
shifter cable runs are typically longer and more convoluted than those
of uprights are, and this can impact shifting in a negative manner.

Small drivewheel bicycles that use larger than normal chainrings
generally have poorer shifting quality - this is true of both recumbents
and small wheel uprights. I had 73/52 chainrings on a bike I used to own
[1] and front shifting was not the best. This is compounded by the lack
of large chainrings with ramps and pins. My current bike uses a clever
step-up jackshaft to avoid this problem and has excellent from shifting.
[2]

Or is it the peculiar arrangements rather than the
mere length?

For reasons of aerodynamics (reduced frontal area) and power production
(angle formed by the seatback, seat base and BB) unfaired performance
recumbents have the BB located higher than the seat. A direct chain run
from the BB to the rear sprocket(s) would pass through the rider.
Therefore, some combination of mid-drive, jackshaft, chain idlers, chain
tensioners and chain tubes is required for chain routing.

Any concrete answers or even wild speculation will
be appreciated, since I'd hate to shoot such rare
creatures just to dissect their chain anatomies.
I can recall only a single tandem sighting in fifteen
years and fear that they may be extinct in these parts.

J.J. Audubon

[1] http://www.ihpva.org/incoming/2001/wbone2.jpg
[2] http://www.ihpva.org/incoming/2002/sunset/Sunset001.jpg

Tom Sherman - Planet Earth