Electric transmission redux

[Jim Smith]

Tom Sherman <[email protected]> writes:

> [email protected] wrote:
>
>> On Sun, 02 Jan 2005 20:31:01 -0600, Jim Smith
>> <[email protected]> wrote:
>>
>>>[email protected] writes:
>>>
>>>
>>>>Our feet stop when they hit the ground at the end of every
>>>>step.
>>>>
>>>>On a bicycle going 20 mph forward, the top of the tire is
>>>>going 40 mph forward and the bottom is going 0 mph forward.
>>>>
>>>>It isn't a matter of what frame of reference anyone likes.
>>>
>>>I can't tell if you are being facetious.
>> [snip]
>> Dear Jim,
>> Our feet stop when they hit the ground at the end of every
>> step.
>> On a bicycle going 20 mph forward, the top of the tire is
>> going 40 mph forward and the bottom is going 0 mph forward.
>> It isn't a matter of what frame of reference anyone likes.
>
> If we use the bicycle wheel as the frame of reference, it is
> motionless, while the bicycle, rider, earth, solar system, Milky Way
> galaxy and the rest of the Universe rotate around it.

The wheel is a bad example because it is a non-inertial frame. The
laws of physics are not guaranteed to hold in a non-inertial frame.
Try and toss one of your shoes to your spouse on the other side of the
wheel, for example, and you will immediately see that your trusted
equations for ballistic motion are not going to be of any use to you.

 

[Jim Smith]

[email protected] writes:

> On Sun, 02 Jan 2005 20:31:01 -0600, Jim Smith
> <[email protected]> wrote:
>
>>[email protected] writes:
>>
>>> Our feet stop when they hit the ground at the end of every
>>> step.
>>>
>>> On a bicycle going 20 mph forward, the top of the tire is
>>> going 40 mph forward and the bottom is going 0 mph forward.
>>>
>>> It isn't a matter of what frame of reference anyone likes.
>>
>>I can't tell if you are being facetious.
>
> [snip]
>
> Dear Jim,
>
> Our feet stop when they hit the ground at the end of every
> step.
>
> On a bicycle going 20 mph forward, the top of the tire is
> going 40 mph forward and the bottom is going 0 mph forward.
>
> It isn't a matter of what frame of reference anyone likes.

I still cant tell.

In your preferred reference frame the foot comes to a stop. This does
not change the fact that walking wastes energy by bobbing the center
of mass up and down, while bicycling does not.

 

[Tom Sherman]

Jim Smith wrote:

> Tom Sherman <[email protected]> writes:
>
>
>>[email protected] wrote:
>>
>>
>>>On Sun, 02 Jan 2005 20:31:01 -0600, Jim Smith
>>><[email protected]> wrote:
>>>
>>>
>>>>[email protected] writes:
>>>>
>>>>
>>>>
>>>>>Our feet stop when they hit the ground at the end of every
>>>>>step.
>>>>>
>>>>>On a bicycle going 20 mph forward, the top of the tire is
>>>>>going 40 mph forward and the bottom is going 0 mph forward.
>>>>>
>>>>>It isn't a matter of what frame of reference anyone likes.
>>>>
>>>>I can't tell if you are being facetious.
>>>
>>>[snip]
>>>Dear Jim,
>>>Our feet stop when they hit the ground at the end of every
>>>step.
>>>On a bicycle going 20 mph forward, the top of the tire is
>>>going 40 mph forward and the bottom is going 0 mph forward.
>>>It isn't a matter of what frame of reference anyone likes.
>>
>>If we use the bicycle wheel as the frame of reference, it is
>>motionless, while the bicycle, rider, earth, solar system, Milky Way
>>galaxy and the rest of the Universe rotate around it.
>
>
> The wheel is a bad example because it is a non-inertial frame. The
> laws of physics are not guaranteed to hold in a non-inertial frame.
> Try and toss one of your shoes to your spouse on the other side of the
> wheel, for example, and you will immediately see that your trusted
> equations for ballistic motion are not going to be of any use to you.

I agree that it would be better to use an inertial frame. However, my
intent was to make a point for the benefit of "Dear Carl".

--
Tom Sherman - Near Rock Island

 

[Jim Smith]

Tom Sherman <[email protected]> writes:

> I agree that it would be better to use an inertial frame. However, my
> intent was to make a point for the benefit of "Dear Carl".

Aha. Sorry. I knew you knew, I just wanted to make sure that anyone
who didn't know would know.

 

[[email protected]]

On Sun, 02 Jan 2005 23:49:39 -0600, Jim Smith
<[email protected]> wrote:

>[email protected] writes:
>
>> On Sun, 02 Jan 2005 20:31:01 -0600, Jim Smith
>> <[email protected]> wrote:
>>
>>>[email protected] writes:
>>>
>>>> Our feet stop when they hit the ground at the end of every
>>>> step.
>>>>
>>>> On a bicycle going 20 mph forward, the top of the tire is
>>>> going 40 mph forward and the bottom is going 0 mph forward.
>>>>
>>>> It isn't a matter of what frame of reference anyone likes.
>>>
>>>I can't tell if you are being facetious.
>>
>> [snip]
>>
>> Dear Jim,
>>
>> Our feet stop when they hit the ground at the end of every
>> step.
>>
>> On a bicycle going 20 mph forward, the top of the tire is
>> going 40 mph forward and the bottom is going 0 mph forward.
>>
>> It isn't a matter of what frame of reference anyone likes.
>
>I still cant tell.
>
>In your preferred reference frame the foot comes to a stop. This does
>not change the fact that walking wastes energy by bobbing the center
>of mass up and down, while bicycling does not.

Dear Jim,

Our feet stop when they hit the ground at the end of every
step.

On a bicycle going 20 mph forward, the top of the tire is
going 40 mph forward and the bottom is going 0 mph forward.

It isn't a matter of what frame of reference anyone likes.

Carl Fogel

 

[Werehatrack]

On 2 Jan 2005 12:24:18 -0800, "Dan B." <[email protected]> wrote:

>A Muzi wrote:
>
>><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.

 

[Werehatrack]

On Mon, 03 Jan 2005 04:01:13 GMT, "Leo Lichtman"
<[email protected]> wrote:

>
>"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.

 

[Dale Benjamin]

Hi Richard,

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

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.


> 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.

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

> 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.

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

 

[B.B.]

In article <[email protected]>,
"Leo Lichtman" <[email protected]> wrote:

>"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/

 

[Jim Smith]

"B.B." <[email protected]> writes:

> In article <[email protected]>,
> "Leo Lichtman" <[email protected]> wrote:
>
>>"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?

 

[richard schumacher]

In article <[email protected]>,
Werehatrack <[email protected]> wrote:


> >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.


> 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]

In article <[email protected]>,
A Muzi <[email protected]> wrote:


> 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.

 

[richard schumacher]

In article <[email protected]>,
Werehatrack <[email protected]> wrote:

> 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.

 

[Peter]

richard schumacher wrote:

>>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.

 

[richard schumacher]

In article <[email protected]>,
Peter <[email protected]> wrote:


> 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.

 

[richard schumacher]

In article <[email protected]>,
Peter <[email protected]> wrote:


> 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 [...]"

 

[meb]

On Sun, 2 Jan 2005 15:18:18 +1100, meb
<[email protected]> wrote:

[snip]

>There are a few niches in which the regenerative braking benefits are
>there.
>Extreme stop and go urban commuting-no sense using the
>calipers/drums/discs all the time.
>Recumbents in hilly terrain-most recumbent bikes are weak in climbing
>yet strong on flats- imagine storing up that energy in advance of the
>climb.
>
>I don't think elimination of the chain is the way to go regarding the
>pedals (unless you're talking about mud/ice use)- much of the time you
>need the efficient drive chain of the pedals. However, on a commuter
>bike, eliminating the dirty chain might merrit an efficiency penalty.
>And on amphibious bikes, efficiency from driveline direction changes
>might be less of a penalty than gears/cables/paddlewheels.
>
>As for racing, imaging storing up that energy while in the pack for
>that extra burst at the finish.

Dear Meb,

Imagine an electric motor big enough to power a bicycle and
rider usefully, plus a set of batteries big enough to store
the necessary current--you have to haul it all up a big hill
to charge it, unless you're cheating by plugging it into an
outlet, in which case any motor scooter will run rings
around you with far less fuss.

Imagine that the motor is about 80% efficient (a fantasy)
and that the charging is about 80% efficient (another
fantasy)--at least a third of the power is lost even in
fantasy.

Imagine that you're going downhill in a race under steady
heavy braking that's busily charging your battery while
everyone else who climbed the hill a lot faster without the
heavy electrical equipment zooms even further out of sight
downhill--

Oh, hell, let's imagine my basset hound's legs aren't four
inches long and enter him at the greyhound track.

Notice that there are not even vague figures suggested for
either charging or engine efficiency, not even vague figures
for weight, and not terribly credible figures for how
heavily and slowly the rider would have to brake to achieve
any useful charging.

How long does it take to charge an ordinary car battery with
a charger plugged into an outlet? And how far will a car
battery will push a bicycle and rider and electric engine up
a long climb?

Carl Fogel

Allright, lets consider the weight of some the current production regenerative braking systems.

ZAP DX system 25 lbs with 288 W-H lead acid battery, 400W. Replace with 36W-H NiMH probably around 11 lbs.

EPS System, 18 lbs with 72 W-H NiMH battery, 250W motor

A couple of units not yet available, but nearing availability:
Sanyo System, 18 lbs with 72 W-H 250 W motor
Birkestrand, about 12 lbs with 72 W-H NiMH 500W motor

There are a couple of Chinese systems under development that should put out around 300-400 W in the 10 lbs range with small NiMH battery packs.

ZAP with its roller drive would certainly have a lower efficiency than the 64% round trip efficiency you propose. The others I’d expect a little better.

Certainly viable today in many commuting environs. Would still need enhancements in weight and efficiency to make them practical for competition. You needn't go with large capacity batteries for a regenerative braking system.

For touring, many folks have equipped their cycles with solar collectors for charging the batteries, so there is the additional practicality.

I’d expect a car battery with 750-800 W-H capacity could propel a cyclist 30-45 miles at 15mph on the flats.

 

[Werehatrack]

On Mon, 03 Jan 2005 11:30:03 -0600, richard schumacher
<[email protected]> wrote:

>In article <[email protected]>,
> Peter <[email protected]> wrote:
>
>
>> 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.

 

[[email protected]]

On Tue, 4 Jan 2005 05:17:58 +1100, meb
<[email protected]> wrote:

>
>[email protected] Wrote:
>> On Sun, 2 Jan 2005 15:18:18 +1100, meb
>> <[email protected]> wrote:
>>
>> [snip]
>>
>> >There are a few niches in which the regenerative braking benefits are
>> >there.
>> >Extreme stop and go urban commuting-no sense using the
>> >calipers/drums/discs all the time.
>> >Recumbents in hilly terrain-most recumbent bikes are weak in climbing
>> >yet strong on flats- imagine storing up that energy in advance of the
>> >climb.
>> >
>> >I don't think elimination of the chain is the way to go regarding the
>> >pedals (unless you're talking about mud/ice use)- much of the time
>> you
>> >need the efficient drive chain of the pedals. However, on a
>> commuter
>> >bike, eliminating the dirty chain might merrit an efficiency penalty.
>> >And on amphibious bikes, efficiency from driveline direction changes
>> >might be less of a penalty than gears/cables/paddlewheels.
>> >
>> >As for racing, imaging storing up that energy while in the pack for
>> >that extra burst at the finish.
>>
>> Dear Meb,
>>
>> Imagine an electric motor big enough to power a bicycle and
>> rider usefully, plus a set of batteries big enough to store
>> the necessary current--you have to haul it all up a big hill
>> to charge it, unless you're cheating by plugging it into an
>> outlet, in which case any motor scooter will run rings
>> around you with far less fuss.
>>
>> Imagine that the motor is about 80% efficient (a fantasy)
>> and that the charging is about 80% efficient (another
>> fantasy)--at least a third of the power is lost even in
>> fantasy.
>>
>> Imagine that you're going downhill in a race under steady
>> heavy braking that's busily charging your battery while
>> everyone else who climbed the hill a lot faster without the
>> heavy electrical equipment zooms even further out of sight
>> downhill--
>>
>> Oh, hell, let's imagine my basset hound's legs aren't four
>> inches long and enter him at the greyhound track.
>>
>> Notice that there are not even vague figures suggested for
>> either charging or engine efficiency, not even vague figures
>> for weight, and not terribly credible figures for how
>> heavily and slowly the rider would have to brake to achieve
>> any useful charging.
>>
>> How long does it take to charge an ordinary car battery with
>> a charger plugged into an outlet? And how far will a car
>> battery will push a bicycle and rider and electric engine up
>> a long climb?
>>
>> Carl Fogel
>
>Allright, lets consider the weight of some the current production
>regenerative braking systems.
>
>ZAP DX system 25 lbs with 288 W-H lead acid battery, 400W. Replace
>with 36W-H NiMH probably around 11 lbs.
>
>EPS System, 18 lbs with 72 W-H NiMH battery, 250W motor
>
>A couple of units not yet available, but nearing availability:
>Sanyo System, 18 lbs with 72 W-H 250 W motor
>Birkestrand, about 12 lbs with 72 W-H NiMH 500W motor
>
>There are a couple of Chinese systems under development that should put
>out around 300-400 W in the 10 lbs range with small NiMH battery packs.
>
>
>ZAP with its roller drive would certainly have a lower efficiency than
>the 64% round trip efficiency you propose. The others I’d expect a
>little better.
>
>Certainly viable today in many commuting environs. Would still need
>enhancements in weight and efficiency to make them practical for
>competition. You needn't go with large capacity batteries for a
>regenerative braking system.
>
>For touring, many folks have equipped their cycles with solar
>collectors for charging the batteries, so there is the additional
>practicality.
>
>I’d expect a car battery with 750-800 W-H capacity could propel a
>cyclist 30-45 miles at 15mph on the flats.

Dear Meb,

A much nicer reply than I deserved--thanks. There's no
excuse for my irritability, just an apology.

What's available is an 18-pound system.

Few riders are going to want to haul an extra 18 pounds
around. That's roughly the equivalent of a second bicycle.

Adding solar collector panels is going to add more weight
and wind drag.

The car battery estimate is intriguing, but I think that it
doesn't apply well because it speaks of the flats, while the
regenerative bicycle system relies on rolling very slowly
down hills under steady braking--it won't work in terrain
where 30-45 miles of flat riding is the norm.

Do you know of any tests of such battery-charging bicycle
systems that cut through all our attempts to calculate? That
is, something where the battery bicycle goes up and down
some real hills on a real ride and is compared to the same
rider on normal bicycle?

Carl Fogel

 

[[email protected]]

On Mon, 03 Jan 2005 11:37:37 -0600, richard schumacher
<[email protected]> wrote:

>In article <[email protected]>,
> Peter <[email protected]> wrote:
>
>
>> 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 [...]"

Dear Richard,

The Rohloff planetary non-CVT transmission weighs a pound or
two more and is slightyly less efficient than an ordinary
bicycle derailleur, penalties that some riders with a few
hundred dollars welcome in exchange for what they consider
maintenance and shifting advantages.

(None of them purchase Rohloffs because they like new
gadgets. Certainly not.)

What kind of efficiency do you expect from a CVT planetary
transmission, as opposed to the typical 95% expected from an
ordinary bicycle chain?

(I seem to recall repeated comments that CVT bicycles never
catch on because so much of the power is wasted.)

Carl Fogel