Electric transmission redux

richard schumacher said:

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.

TANSTAAFL. There are substantially greater losses in a
generator/battery/motor system than in a drive chain[1]. The greatest
instantaneous power demand on the rider to maintain a given speed may
be lower than the peak demand with a conventional bike, but the power
required to traverse a given course will be higher for the hybrid than
for the direct-drive for a variety of reasons unless the direct-drive
bike is unusually inefficient or poorly suited to the
application...and this is accentuated in hilly terrain.

Don't let my discouraging statements dissuade you from finding
investors and spending large sums to pursue your goal of devising an
electrically-based hybrid/CVT bike, however. Watching people learn
about thermodynamics has been a lifelong source of amusement for me.

[1] Many people have made the mistake of inferring that the
experience of the builders of hybrid automobiles, that the electric
drive system with battery buffer is more efficient than an
automobile's automatic transmission, would be applicable to other
things. They seem to regularly fail to take into account the fact
that those automatic transmissions are, by comparison to either a
chain drive in fairly poor condition or a conventional manual gearbox,
horribly inefficient. The people who make this mistake often are
regular readers of Popular Science, which often ranks with the Weekly
World News for accuracy over the long haul.
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Quoted message said:

richard schumacher said:

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

-snip-

Werehatrack wrote:
-snip-

Quoted message said:

TANSTAAFL.

-snip-

Quoted message said:

Don't let my discouraging statements dissuade you from finding
investors and spending large sums to pursue your goal of devising an
electrically-based hybrid/CVT bike, however. Watching people learn
about thermodynamics has been a lifelong source of amusement for me.

-snip-

Quoted message said:

horribly inefficient. The people who make this mistake often are
regular readers of Popular Science, which often ranks with the Weekly
World News for accuracy over the long haul.

I already own cars.
I ride my bicycle for many reasons, none of which are
enhanced by Mr Schumacher's format.

TANSTAAFL?

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

A Muzi said:

<snip>
TANSTAAFL?
</snip>

TANSTAAFL=acronym for
There Ain't No Such Thing As A Free Lunch

(Was that originally Robert A. Heinlein's phrase, or did he borrow it
from elsewhere?)

Dan

Sun, 02 Jan 2005 14:18:04 -0600, <[email hidden]>,

A Muzi said:

TANSTAAFL?

There Ain't No Such Thing As A Free Lunch
--
zk

As soon as he can produce an electric vehicle that does not produce any
heat in its battery, generator, motor system I would like to be the
first investor.

In article <[email hidden]>,

Werehatrack said:

richard schumacher said:

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.

TANSTAAFL. There are substantially greater losses in a
generator/battery/motor system than in a drive chain[1]. The greatest
instantaneous power demand on the rider to maintain a given speed may
be lower than the peak demand with a conventional bike, but the power
required to traverse a given course will be higher for the hybrid than
for the direct-drive for a variety of reasons unless the direct-drive
bike is unusually inefficient or poorly suited to the
application...and this is accentuated in hilly terrain.

Don't let my discouraging statements dissuade you from finding
investors and spending large sums to pursue your goal of devising an
electrically-based hybrid/CVT bike, however. Watching people learn
about thermodynamics has been a lifelong source of amusement for me.

Well, if you build/buy sufficiently nice three-pase widgets I hear
those can peak around 95% efficiency in the big ones. I don't know what
that translates to in smaller units: if it's a function of effort in
manufacture rather than physics.
But, assuming you can get reasonably nice three-phase motors in a
decent size to thunk onto a bike frame, you could use three. One,
turned by the crank, generating. One, in the hub, moving the bike. And
a third (connected through a clever power control) acting like a
flywheel battery. Assume that the rider is cranking the generator at
60Hz, output frequency will be a little less, but close enough. That
60Hz, depending on how the motor is wired, could whizz that flywheel
motor around pretty fast--several times the generator's speed. So it
won't have to be as heavy. Send 60Hz to the wheel motor, and you're
off. Varying the frequency by varying pedaling speed would vary ground
speed.
With the clever power controller, while cranking is producing power
it either turns the rear wheel, or, if the rear wheel is already
trucking along at a good speed, spin up the flywheel motor. If the
generator falls behind the wheel speed, pull power from the flywheel.
If the generator's not putting out, but the wheel motor is going faster
than the flywheel, connect the flywheel to the wheel motor, and the rear
motor will act as a generator and spin up the flywheel until its
frequency matches the wheel motor's. Just make sure it never drives the
pedals!
You could probably even set up some sort of speed ratio control by
alternately driving the wheel and charging the flywheel, but your
dynamic range would be limited by how far the motors could get from
ideal speed before dropping off in efficiency. Switch fast enough and
you won't get periods where the pedals feel dead and freewheel too
easily.
Ideally, assuming you have 95% efficient motors, and no losses in the
cables or switches, the system would be ~90% efficient--pedal to wheels.
~81% efficient pedal to flywheel to wheels. But a bad bearing in the
flywheel motor, too much vibration of that motor while running, or
having to drive a little cooling fan would bring that down fast.
Running higher voltages at lower currents will help some and allow
smaller motors, but that can get dangerous to the rider and you'll
probably pay for it in the switching electronics.
And I think most motors have around a 10% operating envelope where
efficiency is reasonable. Too far outside that starts burning windings
from all the waste heat. A person probably couldn't put out enough
juice to really fry a motor, but he sure would get tired in a hurry.
Then, of course, you have the problem that some riders might pedal too
slowly to generate useful output. In any event, the generator's
frequency would need to exceed the wheel motor's by a good bit before
you go anywhere--might make starting tricky.
And don't go too fast--could make the flywheel explode.
DC electrical with a speed controller might be better, but rectifying
AC to make DC wastes power, and direct DC generators over a fraction of
an amp are always inefficient from what I've seen. Besides, batteries
are weighty.
Could go for a compromise--a regular chain drive, with a
motor/generator/flywheel setup along side. Ride like normal, but if
you're coasting down a hill too fast, connect the flywheel--it'll rev
up, slowing the bike, and then return some power when climbing the other
side. Flip it off (of have it flip itself off) once the flywheel is no
longer helping. That would be pretty nice on a long descent, wouldn't
pop tires, give a little boost on the climb back up, and might be
reasonably lightweight. Would sound awesome, too, when the flywheel's
revving up! Wouldn't even need a cooling fan if used intermittently
like that.
Personally, I'd to hydrostatic with an accumulator. Probably more
efficient, and definitely more manly. Imagine hopping on the bike in
front of everyone, flipping a little lever, and peeling out! (:

--
B.B. --I am not a goat! thegoat4 at airmail dot net
http://web2.airmail.net/thegoat4/

"B.B." wrote: (clip) batteries are weighty.(clip)
^^^^^^^^^^^^^^^
I do believe that a flywheel capable of storing as much energy as a battery
will be even more "weighty." If you are fortunate enough to come home with
a charged battery, it will still be there to help you start your next ride.
A flywheel will lose most or all of its energy soon after the end of your
ride, so you go out each time with a big "millstone".

You have a lot of imagination--do you write science fiction on your day job?
<G>

Dan B. said:

A Muzi said:

<snip>
TANSTAAFL?
</snip>

TANSTAAFL=acronym for
There Ain't No Such Thing As A Free Lunch

(Was that originally Robert A. Heinlein's phrase, or did he borrow it
from elsewhere?)

AFAIK, he was the first to turn it into an acronymic expression, but
the expanded phrase was a common aphorism in the US before that. My
parents related that it was in the common vernacular well before WWII.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

Leo Lichtman said:

"B.B." wrote: (clip) batteries are weighty.(clip)
^^^^^^^^^^^^^^^
I do believe that a flywheel capable of storing as much energy as a battery
will be even more "weighty." If you are fortunate enough to come home with
a charged battery, it will still be there to help you start your next ride.
A flywheel will lose most or all of its energy soon after the end of your
ride, so you go out each time with a big "millstone".

You have a lot of imagination--do you write science fiction on your day job?
<G>

And if not, maybe it's time to do it after work and start submitting
the results. Who knows, he could be the next Harlan Ellison. No,
scratch that, we've got more of those than most people can stand
now...better he should be the next Larry Niven.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

Hi Richard,

"richard schumacher" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

In an earlier post on the subject it was stated that electric CVTs in

a

Quoted message said:

bicycle are impractical because there is no excess power to be had.

But

Quoted message said:

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

Quoted message said:

a freebie.

You're right, there is sometimes excess power to be had, but it is
trivial compared to what the rider expends. The losses incurred
converting it to electricity, storing it, and converting it back into
mechanical power are substantial, I think you won't get 5% back. And
you'll be adding a lot of weight with a motor, battery, generator; and
complexity - the simple brake calipers we now use will have to be
replaced with something that advises a computer of the desired braking
effect.

Quoted message said:

This system is certainly not for racers. Peak instantaneous

efficiency

Quoted message said:

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

Quoted message said:

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.

Nope. The greater weight of the system and the inefficiencies involved
suggest there will rarely be any perceived lesser effort.

Quoted message said:

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

Quoted message said:

conventional bike there are only discrete values of proportion

available

Quoted message said:

(gears), whereas in an electric drive a continuous range of values is
available.

How about getting the effort the rider is exerting on the crank into the
picture? Seven usable gear ratios are plenty.

In article <[email hidden]>,

Leo Lichtman said:

"B.B." wrote: (clip) batteries are weighty.(clip)
^^^^^^^^^^^^^^^
I do believe that a flywheel capable of storing as much energy as a battery
will be even more "weighty." If you are fortunate enough to come home with
a charged battery, it will still be there to help you start your next ride.
A flywheel will lose most or all of its energy soon after the end of your
ride, so you go out each time with a big "millstone".

You have a lot of imagination--do you write science fiction on your day job?
<G>

Nah. I was thinking of the problem in terms of stop & get going
again usage, not charge and cruise around usage. In a stop&go kind of
application a flywheel has much better power density than a lead-acid
battery. And better efficiency of charging and discharging, which was
my main reason for picking a flywheel for a hypothetical system.
Besides, in an electric system on a bike the chances of coming home with
a charged battery are low anyway.
FYI, Flywheel energy = Wv^2/2g, W being weight and v being rim
velocity. so increasing speed pays off faster than increasing mass.
That's why I suggested speeding up the flywheel to reduce its mass in my
first post.
But yeah, if it were meant to replace a battery as a long-term
storage device it would become impractical on a bike as flywheel
batteries need funky stuff like vacuum cases and magnetic bearings. The
case would be too heavy and bulky and the bearings hate being jiggled
around.
However, flywheel "batteries" do exist, have been used all over, and
are quite a bit smaller than the equivalent chemical battery system.
Low maintenance to boot.
I don't write sci-fi, but I used to read a bunch when I was in high
school. (:

--
B.B. --I am not a goat! thegoat4 at airmail dot net
http://web2.airmail.net/thegoat4/

B.B. said:

In article <[email hidden]>,

Leo Lichtman said:

"B.B." wrote: (clip) batteries are weighty.(clip)
^^^^^^^^^^^^^^^
I do believe that a flywheel capable of storing as much energy as a battery
will be even more "weighty." If you are fortunate enough to come home with
a charged battery, it will still be there to help you start your next ride.
A flywheel will lose most or all of its energy soon after the end of your
ride, so you go out each time with a big "millstone".

You have a lot of imagination--do you write science fiction on your day job?
<G>

Nah. I was thinking of the problem in terms of stop & get going
again usage, not charge and cruise around usage. In a stop&go kind of
application a flywheel has much better power density than a lead-acid
battery. And better efficiency of charging and discharging, which was
my main reason for picking a flywheel for a hypothetical system.
Besides, in an electric system on a bike the chances of coming home with
a charged battery are low anyway.
FYI, Flywheel energy = Wv^2/2g, W being weight and v being rim
velocity. so increasing speed pays off faster than increasing mass.
That's why I suggested speeding up the flywheel to reduce its mass in my
first post.
But yeah, if it were meant to replace a battery as a long-term
storage device it would become impractical on a bike as flywheel
batteries need funky stuff like vacuum cases and magnetic bearings. The
case would be too heavy and bulky and the bearings hate being jiggled
around.
However, flywheel "batteries" do exist, have been used all over, and
are quite a bit smaller than the equivalent chemical battery system.
Low maintenance to boot.
I don't write sci-fi, but I used to read a bunch when I was in high
school. (:

I wonder what the gyroscopic effects of flywheel battery would be like
on a bicycle. I am thinking of the autonomous motorcycle built at
Berkeley for the DARPA grand challenge. It can balance at rest by
shoving a gyroscope around and can generate a large enough moment to
right the bike if it falls over, so the forces are considerable. I
haven't thought this through, but I suppose if the flywheel was fully
gimbaled it would not affect the handling, or would it? I suppose one
could use the flywheel instead of a kickstand too. Come to think of
it, I suppose if the gimbals were locked, and the flywheel had enough
angular momentum, the bicycle would be un-ridable. This might make a
useful anti-theft device. I am picturing a bicycle that stays upright
wherever you leave it and cannot be ridden until it recognizes your
fingerprint on the grip, or something. I wonder if there is prior art
on that?

In article <[email hidden]>,

Werehatrack said:

Quoted message said:

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.

TANSTAAFL. There are substantially greater losses in a
generator/battery/motor system than in a drive chain[1].

Generators and motors can exceed 90%. Wet, dirty chain drives can be
under 80%. But for sake of argument assume for the moment that chains
are always more efficient.

Quoted message said:

The greatest
instantaneous power demand on the rider to maintain a given speed may
be lower than the peak demand with a conventional bike, but the power
required to traverse a given course will be higher for the hybrid than
for the direct-drive for a variety of reasons unless the direct-drive
bike is unusually inefficient or poorly suited to the
application...and this is accentuated in hilly terrain.

Of course the total energy required will be greater. This isn't about
efficiency, it's about comfort for the rider. A little efficiency can
be traded for a little more pleasure.

I should also have made explicit that a bike with an electric
transmission should like any existing e-bike have the option of
recharging from a wall socket. Only a fanatic would want an electric
bike that was entirely human powered.

In article <[email hidden]>,

A Muzi said:

I already own cars.
I ride my bicycle for many reasons, none of which are
enhanced by Mr Schumacher's format.

TANSTAAFL?

There Ain't No Such Thing As A Free Lunch. Often used by fans of dead
scifi writer Robert Heinlein.

Again, the point is not to increase efficiency. People ride bikes for a
variety of reasons, not all of which are best served by the same format.

In article <[email hidden]>,

Werehatrack said:

The greatest
instantaneous power demand on the rider to maintain a given speed may
be lower than the peak demand with a conventional bike, but the power
required to traverse a given course will be higher for the hybrid than
for the direct-drive for a variety of reasons unless the direct-drive
bike is unusually inefficient or poorly suited to the
application...and this is accentuated in hilly terrain.

Of course the total energy required will be greater. This isn't about
efficiency, it's about comfort for the rider. A little efficiency can
be traded for a little more pleasure.

I should also have made explicit that a bike with an electric
transmission should like any existing e-bike have the option of
recharging from a wall socket. Only a fanatic would want an electric
bike that was entirely human powered.

richard schumacher said:

Quoted message said:

The greatest
instantaneous power demand on the rider to maintain a given speed may
be lower than the peak demand with a conventional bike, but the power
required to traverse a given course will be higher for the hybrid than
for the direct-drive for a variety of reasons unless the direct-drive
bike is unusually inefficient or poorly suited to the
application...and this is accentuated in hilly terrain.

Of course the total energy required will be greater. This isn't about
efficiency, it's about comfort for the rider. A little efficiency can
be traded for a little more pleasure.

Increasing the total amount of work I need to do to propel my bicycle
from A to B is unlikely to either increase my comfort or provide
greater pleasure.

In article <[email hidden]>,

Peter said:

Increasing the total amount of work I need to do to propel my bicycle
from A to B is unlikely to either increase my comfort or provide
greater pleasure.

You're right, there is a better way to do this. Adapt Toyota's system
of an electrically-controlled planetary gear transmission, substituting
it for the chain and derailleur on an electric bike. That way you'd get
both the efficiency benefit of direct mechanical drive and on-demand
electric motor assist. It wouldn't have to be much bigger or heavier
than existing internally-geared hubs and would be completely sealed.

In article <[email hidden]>,

Peter said:

Increasing the total amount of work I need to do to propel my bicycle
from A to B is unlikely to either increase my comfort or provide
greater pleasure.

You're right, there is a better way to do this. Adapt Toyota's system
of a continuously-variable planetary gear transmission (1), substituting
it for the chain and derailleur on an electric bike. That way you'd get
the efficiency benefit of direct mechanical drive, continuously variable
gear ratio, and on-demand electric motor assist. It wouldn't have to be
much bigger or heavier than existing internally-geared hubs and would be
completely sealed.

(1) see here for a description
http://home.earthlink.net/~graham1/MyToyotaPrius/PriusFrames.htm
click on "Understanding [...]"

richard schumacher said:

In article <[email hidden]>,

Peter said:

Increasing the total amount of work I need to do to propel my bicycle
from A to B is unlikely to either increase my comfort or provide
greater pleasure.

You're right, there is a better way to do this. Adapt Toyota's system
of an electrically-controlled planetary gear transmission, substituting
it for the chain and derailleur on an electric bike. That way you'd get
both the efficiency benefit of direct mechanical drive and on-demand
electric motor assist. It wouldn't have to be much bigger or heavier
than existing internally-geared hubs and would be completely sealed.

At an increased driveline drag penalty, and a doubling of the cost of
the bike, in one go.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.