Re: Shaft Drive Bikes
On 2 Aug 2006 23:08:59 -0700, "Blair P. Houghton"
>> Replacing the chain with a shaft drive would only make the internal
>> hubs even less efficient.
>What in the data you linked leads you to claim that?
>There's a name for that fallacy.
You're right. I skipped a step.
I should have added that in typical motorcycle primary transmissions,
dynometer testing showed long ago that chains lose about 3% of the
engine power, while gears lose about 5%.
Or quoted something familiar to gear-vs-chain debates, like this Wiki
"Shaft-driven bikes have a large bevel gear where a conventional bike
would have its chainring. This would mesh to another bevel gear
mounted on the driveshaft. The use of bevel gears allows drive from
the pedals to be turned through 90 degrees. The driveshaft then has
another bevel gear near the rear wheel hub which mesh to a bevel gear
on the hub where the rear sprocket would be on a conventional bike.
The 90-degree change of plane, for the drive, that occurs at the
bottom bracket and again at the rear hub requires the use of bevel
gears. Bevel gears are notorious for their lack of efficiency as much
power is lost to friction. However, bevel gears are more efficient
than the alternative methods of turning drive through 90 degrees, like
worm gears or crossed helical gears."http://en.wikipedia.org/wiki/Shaft-driven_bicycle
Two pairs of gears at 90 degrees are just not efficient compared to
chains running in line.
With that in mind, the argument a fortiori ensues:
Replacing a chain with 2 pairs of inefficient bevel gears and then
running the power through another set of bevel gears in a hub will