i*********5
发帖数: 19210 | 1 I was at Interbike for the first time this year, and a big trend was crank
arm-based power meters. There were at least three there:
Rotor Power,
Pioneer, and
StagesOne.
The fundamental physics behind each of these three units is the same: to
propel the bike force is transmitted via a mechanical path: pedal body to
pedal spindle to crank arm to (left side only) bottom bracket spindle to
spider to chainring to chain to cassette to free hub body to spokes to rim
to tires to road.
You can in theory extract propulsive torque anywhere along this path, and
when combined with rate of rotation, convert the torque into power. In the
case of the crank arm-based models, torque applied to the crank arm bends it
, a bending moment proportional to the torque. To decent approximation the
bending is proportional to the moment, and is thus proportional to the
torque, so if you can measure bending then with suitable calibration (for
example, hanging a known mass from a pedal orientated horizontally) you can
determine the torque.
http://djconnel.blogspot.ca/2012/09/interbike-2012-crankarm-bas |
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