R
richard schumacher
Guest
In an earlier post on the subject it was stated that electric CVTs in a
bicycle are impractical because there is no excess power to be had. But
there often is excess power available: whenever one coasts downhill or
otherwise does not pedal a conventional bike because one's speed is
already great enough, on an electric drive bike one could continue
pedaling to store energy in the battery for later use. This is in
addition to the energy that can be recovered simultaneously by
regenerative braking. The chief benefit of an electric transmission
with a battery is this load leveling capability; the CVT feature is just
a freebie.
This system is certainly not for racers. Peak instantaneous efficiency
will be less than in a chain drive (chains are great under ideal
conditions, that is when they are perfectly lubricated and free of dirt
or water). But the perceived effort required will be less under many
conditions because the rider can always put muscle energy into the
system when and as desired, independent of ground speed. This is what
many casual riders want.
A chainless all-electric drive could also have the simplest possible
control set, namely a brake and a "shift" control as in a conventional
bike. There need be no separate throttle for the electric motor. The
control system would be programmed so that drive wheel RPM is in
proportion to crank RPM, with the proportionality set by the shift
controlr. This is as in a conventional bike, except of course that in a
conventional bike there are only discrete values of proportion available
(gears), whereas in an electric drive a continuous range of values is
available.
bicycle are impractical because there is no excess power to be had. But
there often is excess power available: whenever one coasts downhill or
otherwise does not pedal a conventional bike because one's speed is
already great enough, on an electric drive bike one could continue
pedaling to store energy in the battery for later use. This is in
addition to the energy that can be recovered simultaneously by
regenerative braking. The chief benefit of an electric transmission
with a battery is this load leveling capability; the CVT feature is just
a freebie.
This system is certainly not for racers. Peak instantaneous efficiency
will be less than in a chain drive (chains are great under ideal
conditions, that is when they are perfectly lubricated and free of dirt
or water). But the perceived effort required will be less under many
conditions because the rider can always put muscle energy into the
system when and as desired, independent of ground speed. This is what
many casual riders want.
A chainless all-electric drive could also have the simplest possible
control set, namely a brake and a "shift" control as in a conventional
bike. There need be no separate throttle for the electric motor. The
control system would be programmed so that drive wheel RPM is in
proportion to crank RPM, with the proportionality set by the shift
controlr. This is as in a conventional bike, except of course that in a
conventional bike there are only discrete values of proportion available
(gears), whereas in an electric drive a continuous range of values is
available.