> >>>> When one is trying to recover the energy of a moving vehicle or
> >>>> object slowing down one has a problem. The energy is proportional
> >>>> to the square of the axle RPM so at first there is a lot of energy
> >>>> recovery and
> >>>> braking effect. As the vehicle slows down the braking energy rapidly
> >>>> falls off.
> >>>> If a generator is directly connected to the wheel the braking
effect of
> >>>> the
> >>>> generator and energy recovery will fall off directly
proportional to the
> >>>> RPM.
> >>>> This is not what is required to stop as quick as possible. The
> >>>> conventional
> >>>> brakes must be applied I suspect unless some way is found to rapidly
> >>>> increase
> >>>> the load on the generator such as changing gear ratios and/or by
> >>>> electronic
> >>>> means. The same thing can be said about spinning up a flywheel
to store
> >>>> the
> >>>> braking energy. This device, invented in the early seventeen
hundreds,
> >>>> might be
> >>>> used to speed up the flywheel or generator as the vehicle comes to a
> >>>> stop
> >>>> then is reset to wait for the next stop.
> >>>>
> >>>> http://www.sailtexas.com/long.html
> >>>> http://www.antique-pocket-watch.com/sinclair-harding.html
> >>>>
> >>>> It will be very interesting next year when KERS is implemented in
> >>>> Formula
> >>>> 1
> >>>> to see how the various teams achieve storing braking energy in a
> >>>> flywheel.
> >>>>
> >>> Paul Lamar
> >>>
> >>>
> >>> Paul,
> >>>
> >>> If the drive train is influenced by the motor cum generator, the duty
> >>> cycle can be increased as the car slows down. Accelerometers are
solid
> >>> state and cheap to provide the necessary signal to maintain the
desire
> >>> rate. The control circuit fits on a quarter. Same challenge
encountered
> >>> in slowing a low mass wind turbine rotor that has been hit with a
micro
> >>> gust. I do agree that flywheels are a more logical way to store
energy
> >>> however. More efficient than say, electro chemical batteries.
They can
> >>> be electro-magnetically or mechanically coupled through the use of
> >>> ferro fluids that change viscosity depending on the small amount of
> >>> current applied to them. Back in the late 1970s flywheel energy
storage
> >>> systems were all the rage and then suddenly the technology
dropped from
> >>> sight. Perhaps the researchers got side tracked by the PacMan
computer
> >>> game craze:) Since then stable homogenous ferro magnetic fluids
and air
> >>> bearings have been perfected along with certain ceramics that
will turn
> >>> to (super heated?) dust if the outer Kevlar protective casing is
> >>> breached.
> >>>
> >>> The amount of energy a flywheel can store is both amazing and
> >>> frightening. This percieved danger may be the reason the
technology was
> >>> not accepted readily. Witness the damage a truck wheel and tire can
> >>> cause when it comes off and hits a house. I wonder if the gyroscopic
> >>> effects influence the handling of the vehicle?
> >>>
> >>>
> >>> Doug in Japan
> >>
> >> Wait a minute... Isn't the amount of energy available related to the
> >> speed. But, the acceleration is related to the braking force
> >> available (traction on tires)? If so, as a vehicle slows, the
> >> energy available at a constant deceleration should diminish. The
> >> coefficient of friction on the tires won't noticeably change with
> >> speed (ignoring aerodynamics).
> >>
> >> I think this makes sense as slowing from 70-60 mph in 2 sec should
> >> require transferring much more energy than slowing from 15-5 mph in
> >> the same amount of time...
> >>
> >> Ke = 1/2 * m * v^2
> >>
> >> deltaKe = 1/2 * m * (v2^2 - v1^2) which is not equal to 1/2 * m *
(v2 -
> >> v1)^2
> >>
> >> My point is that if you make the motor system large enough to put a
> >> constant energy load on the tires, they will lock up. In order to
> >> maintain maximum braking force you may need gear up the motor for
> >> adequate braking at very low speeds - due to motor inefficiency, but
> >> not much.
> >>
> >>
> >>
> >> Matt-
> >>
> >> That was what I was trying to say but I think you mean generator
> >> and not motor. Yes I know... same o same o but the motor is in
generator
> >> mode.
> >>
> >> Paul Lamar
> >
> >
> > Still not sure we're on the same page. I think having a single ratio
> > drive to the regen generator/motor is perfectly adequate - a cvt or
> > other variable ratio drive is not necessary. The bulk of the energy
> > available is going to come from slowing from a high speed. The regen
> > energy available from a slow speed is negligible.
> >
> > Storing energy to a flywheel certainly requires a different approach -
> > accelerating the flywheel while decelerating the car.
> >
> >
> > Regards,
> >
> > Matt-
> >
> >
> > Well You could be right. Maybe we don't have to change the ratio.
> > How do you propose speeding up the flywheel as the car slows?
> >
> > Paul Lamar
>
>
> Like I said.. The all mechanical storage system (flywheel) requires
> something different. If weight weren't a concern, I'll bet an
> electric-electric system would be as efficient as anything else - the
> wheel motors become generators while braking, driving a motor which
> mechanically turns the flywheel - probably gear the flywheel to turn
> faster than the motor. It might be difficult to design a motor which
> would survive at the RPM required to make the flywheel efficient
> (v-squared term dominates). It could be worth trying though as
> integrating the motor into the flywheel would dramatically simplify
> the system.
>
> The electrical portion of the system is reversed to recover power from
> the flywheel.
>
>
> Matt-
>
> Well we shall see as weight is everything in a Formula 1 car.
>
> Paul Lamar

A Late Addition Because of Political Correctness :-)

Matt, you wrote: "If weight weren't a concern, I'll bet an
electric-electric system would be as efficient as anything else - the
wheel motors become generators while braking, driving a motor which
mechanically turns the flywheel - probably gear the flywheel to turn
faster than the motor."

Welll . . . in all fairness to MY favorite obsession, the hydraulic
transmission ("hybrid"), fluid would turn the motors to drive the
vehicle forward.  When it is time to slow down, the system reverses the
flow of hydraulic fluid.  The motors turn immediately into pumps.  They
pump the fluid into a pressurized collector, the accumulator.

Hydraulic transmission of power and regeneration of power possess
advantages over doing the same tasks electrically.  "A gas/electric
hybrid recovers 30 percent of braking energy, while a hydraulic hybrid
can recover 70 percent, contributing to better efficiency [source:
_NextEnergy_
<http://howstuffworks.com/framed.htm?parent=hydraulic-hybrid.htm&url=http://www.nextenergy.org/industryservices/Hybrid__Hydraulics.asp>]."
. . . "Another payoff is the efficiency of the hydraulic components
themselves. Because the components are lightweight and use simple
mechanics, they're easy to build, maintain and repair."(source:
http://auto.howstuffworks.com/hydraulic-hybrid3.htm).

True, Paul: an hydraulic "hybrid" driving a car at a steady speed over
the Interstate/Autobahn/autostrada/autoroute will not yield great,
green, gobs of free, regenerated energy, but a _race car_ (the topic
_is_ the Formula 1 KERS system), which accelerates and brakes suddenly
and often, might benefit much from an hydraulic transmission of power to
the wheels.

And now, all three approaches to recovering energy:
* mechanical KERS
* electrical hybrid
* hydraulic regeneration
are represented in this discussion. :-)

Guys, to be clear: "Political Correctness" was used _solely_ as humor!
I am not saying that anyone on this forum lacks political perspicacity
or any level of correctness.  I am _just_ _kidding_!  :-)

Les Nordman :-)