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"Continuously variable" electric transmission



 
 
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  #1  
Old December 8th 03, 04:43 AM
Richard Schumacher
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Default "Continuously variable" electric transmission

My searches have not turned up anyone selling a bicycle with a
continuously variable electric transmission. I don't mean an electric
scooter: I mean one in which the crank turns a generator/alternator,
whose output through an electronic controller then drives an electric
motor on the wheel rim(s) or in the hub(s). There would be no chain,
derailleur or gears, except perhaps for some fixed-ratio gearing inside
the generator/alternator or motor assemblies. A control equivalent to a
shift lever sets the ratio between crank torque and RPMs, which can be
varied over some wide range. The rider sets the speed by changing this
ratio and/or the crank RPMs as they find comfortable. Scooter-type
assist would be possible through use of an optional battery. (Earlier
threads on the subject addressed mechanical CVTs and auto-shift
mechanisms, not an all-electric transmission.)

What's the point? Mostly geekiness, I suppose, but the effectively
infinite number of "gears" while reducing the number of moving parts is
appealing. Also appealing is the notion that a battery in the system
would provide load-levelling (hill assist) but with the rider still
ultimately providing all of the energy, unless of course the rider
cheats by re-charging the battery from an external source. For
non-cheaters :_ the battery need only be large enough to help climb one
hill. Efficiency would not be as good as with a conventional drive, but
that's not really a concern for commuters or pleasure riders.

Surely by now someone must make such a thing?

Ads
  #2  
Old December 8th 03, 05:19 AM
David L. Johnson
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Default "Continuously variable" electric transmission

On Sun, 07 Dec 2003 21:43:10 +0000, Richard Schumacher wrote:

My searches have not turned up anyone selling a bicycle with a
continuously variable electric transmission. I don't mean an electric
scooter: I mean one in which the crank turns a generator/alternator, whose
output through an electronic controller then drives an electric motor on
the wheel rim(s) or in the hub(s).

snippage
*Efficiency
would not be as good as with a conventional drive, but that's not really a
concern for commuters or pleasure riders.


Efficiency would indeed be a concern for commuters and pleasure riders if
the efficiency is low enough, as I would presume would be the case. You
have three separate sources of energy loss: the inefficiency of the
generator, the power transmission to the motors, and the motors
themselves. Do you ever notice an electric motor getting hot? That's
wasted energy, and that gets worse as load increases.

The engineers can give reasonable estimates on the energy losses.

--

David L. Johnson

__o | Deserves death! I daresay he does. Many that live deserve
_`\(,_ | death. And some that die deserve life. Can you give it to
(_)/ (_) | them? Then do not be too eager to deal out death in judgement.
-- J. R. R. Tolkien

  #3  
Old December 8th 03, 01:58 PM
David Kerber
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Default "Continuously variable" electric transmission

In article ,
says...
My searches have not turned up anyone selling a bicycle with a
continuously variable electric transmission. I don't mean an electric
scooter: I mean one in which the crank turns a generator/alternator,
whose output through an electronic controller then drives an electric
motor on the wheel rim(s) or in the hub(s). There would be no chain,
derailleur or gears, except perhaps for some fixed-ratio gearing inside
the generator/alternator or motor assemblies. A control equivalent to a
shift lever sets the ratio between crank torque and RPMs, which can be
varied over some wide range. The rider sets the speed by changing this
ratio and/or the crank RPMs as they find comfortable. Scooter-type
assist would be possible through use of an optional battery. (Earlier
threads on the subject addressed mechanical CVTs and auto-shift
mechanisms, not an all-electric transmission.)

What's the point? Mostly geekiness, I suppose, but the effectively
infinite number of "gears" while reducing the number of moving parts is
appealing. Also appealing is the notion that a battery in the system
would provide load-levelling (hill assist) but with the rider still
ultimately providing all of the energy, unless of course the rider
cheats by re-charging the battery from an external source. For
non-cheaters :_ the battery need only be large enough to help climb one
hill. Efficiency would not be as good as with a conventional drive, but
that's not really a concern for commuters or pleasure riders.

Surely by now someone must make such a thing?


I doubt it. The loss in efficiency over a mechanical
transmission would make most any ride a real chore.

--
Dave Kerber
Fight spam: remove the ns_ from the return address before replying!

REAL programmers write self-modifying code.
  #5  
Old December 8th 03, 04:12 PM
Mike Farnes
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Default "Continuously variable" electric transmission

Richard Schumacher wrote
My searches have not turned up anyone selling a bicycle with a
continuously variable electric transmission. I don't mean an electric
scooter: I mean one in which the crank turns a generator/alternator,
whose output through an electronic controller then drives an electric
motor on the wheel rim(s) or in the hub(s).sure riders.

...

Surely by now someone must make such a thing?


I don't think you'll find anything in production but there's an
article about such a thing he

http://petrix.dreifels.ch/fb/images/1_wsj_shorter_1.pdf

Regards,
Mike
  #6  
Old December 8th 03, 06:32 PM
Jeff Wills
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Default "Continuously variable" electric transmission

Richard Schumacher wrote in message ...
My searches have not turned up anyone selling a bicycle with a
continuously variable electric transmission.

SNIP
Surely by now someone must make such a thing?


Search through the IHPVA archives at www.ihpva.org . I believe
Andreas Fuchs was designed such a device and has built working models.

Jeff
  #7  
Old December 8th 03, 09:01 PM
Bill Hennessy
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Default "Continuously variable" electric transmission

I've been thinking the same thing. But, I know of no one who makes such a
thing. Yes, I've looked.


  #8  
Old December 8th 03, 10:49 PM
F1
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Default "Continuously variable" electric transmission


"Richard Schumacher" wrote in message
...
My searches have not turned up anyone selling a bicycle with a
continuously variable electric transmission. I don't mean an electric
scooter: I mean one in which the crank turns a generator/alternator,
whose output through an electronic controller then drives an electric
motor on the wheel rim(s) or in the hub(s). There would be no chain,
derailleur or gears, except perhaps for some fixed-ratio gearing inside
the generator/alternator or motor assemblies. A control equivalent to a
shift lever sets the ratio between crank torque and RPMs, which can be
varied over some wide range. The rider sets the speed by changing this
ratio and/or the crank RPMs as they find comfortable. Scooter-type
assist would be possible through use of an optional battery. (Earlier
threads on the subject addressed mechanical CVTs and auto-shift
mechanisms, not an all-electric transmission.)

What's the point? Mostly geekiness, I suppose, but the effectively
infinite number of "gears" while reducing the number of moving parts is
appealing. Also appealing is the notion that a battery in the system
would provide load-levelling (hill assist) but with the rider still
ultimately providing all of the energy, unless of course the rider
cheats by re-charging the battery from an external source. For
non-cheaters :_ the battery need only be large enough to help climb one
hill. Efficiency would not be as good as with a conventional drive, but
that's not really a concern for commuters or pleasure riders.

Surely by now someone must make such a thing?



Unlike a gas fueled internal combustion motor, an electric motor's peak
torque is 0 rpm, so no transmission is needed. A single gearing is used for
whatever your primary speed will be.


  #9  
Old December 9th 03, 01:05 AM
F1
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Posts: n/a
Default "Continuously variable" electric transmission

Actually, this might be easier...

http://lancet.mit.edu/motors/motors3.html#tscurve


  #10  
Old December 9th 03, 01:28 AM
David Kerber
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Posts: n/a
Default "Continuously variable" electric transmission

In article . net,
says...

"Richard Schumacher" wrote in message
...
My searches have not turned up anyone selling a bicycle with a
continuously variable electric transmission. I don't mean an electric
scooter: I mean one in which the crank turns a generator/alternator,
whose output through an electronic controller then drives an electric
motor on the wheel rim(s) or in the hub(s). There would be no chain,
derailleur or gears, except perhaps for some fixed-ratio gearing inside
the generator/alternator or motor assemblies. A control equivalent to a
shift lever sets the ratio between crank torque and RPMs, which can be
varied over some wide range. The rider sets the speed by changing this
ratio and/or the crank RPMs as they find comfortable. Scooter-type
assist would be possible through use of an optional battery. (Earlier
threads on the subject addressed mechanical CVTs and auto-shift
mechanisms, not an all-electric transmission.)

What's the point? Mostly geekiness, I suppose, but the effectively
infinite number of "gears" while reducing the number of moving parts is
appealing. Also appealing is the notion that a battery in the system
would provide load-levelling (hill assist) but with the rider still
ultimately providing all of the energy, unless of course the rider
cheats by re-charging the battery from an external source. For
non-cheaters :_ the battery need only be large enough to help climb one
hill. Efficiency would not be as good as with a conventional drive, but
that's not really a concern for commuters or pleasure riders.

Surely by now someone must make such a thing?



Unlike a gas fueled internal combustion motor, an electric motor's peak
torque is 0 rpm, so no transmission is needed.


Not necessarily; it depends on the motor design: induction motors tend
to have their peak at low but non-zero speeds unless they have a
capacitor start, while synchronous motors have essentially zero starting
torque, and shaded-pole motors have very low starting torque. DC motors
can have pretty much whatever torque characteristics you want to design
into them.

A single gearing is used for
whatever your primary speed will be.


True; it's easy to design an electric motor to run at a huge range of
speeds, and with sophisticated electronic controls, the efficiency
doesn't decrease a whole lot over that range, either.

--
Dave Kerber
Fight spam: remove the ns_ from the return address before replying!

REAL programmers write self-modifying code.
 




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