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Consider, if you will, a device that could store torque while
it's being generated but not doing useful work, such as when a
car is idling at a stoplight, and release it when it is useful,
such as immediately upon takeoff from said stoplight. It
would use essentially the same spring mechanism
as a windup
watch, but on a larger scale. Excess torque could also be
stored while coasting downhill, to be reapplied on a
subsequent uphill climb. As a side benefit, if there is leftover
torque when the car stops, it can be used to help crank the
engine in case the battery is a bit weak.
Be the flywheel
Be_20the_20Flywheel
Here is my spin on this concept. [bungston, Apr 18 2011]
[link]
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It is called regenerative braking, and it isn't stored in "lossy" springs. It is stored in "lossy" batteries. |
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Alteratively it is called a flywheel, and is baked, possibly WKTE. |
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Of course you may be refering to the modular clock-spring unit contained within the "Home-Sweat-Home" project, which seemed to have been rent-downunda by a particularly sensitive antipodean. |
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Regenerative braking requires an electric motor, either as
the sole method of propulsion or as part of a hybrid
system. This is just a single component that only requires
a slight modification to an existing powertrain design.
Also, regenerative braking only generates energy while
braking, whereas the primary purpose of this is to store
energy generated while the engine is idling that would
otherwise be going to waste. Many cars that employ
regenerative braking are able to shut off the engine while
the vehicle is stopped, nullifying this loss. |
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One could use a flywheel for this design, but those have
their own problems, including frictional energy loss
(making it hard to store energy for a long period of time),
and overall would represent a more complicated design,
with a lot more moving parts. |
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And with either method, you have the problem of scale.
If your electric motor can only generate so much torque,
the only way to increase that is to put in a bigger and
more expensive motor. You could spin your flywheel
faster, or make it heavier, but then you run into tricky
materials engineering problems, not to mention the
increase in gyroscopic forces that would have a negative
effect on the handling of the car. With this system, all
you need to do to increase the amount of power available
is use a bigger or stiffer spring, and perhaps change the
gear ratios on the input and output shafts. |
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//With this system, all you need to do to increase the amount of power available is use a bigger or stiffer spring// You forgot to mention a heavier, more expensive, and possibly made from Unobtainium, spring. I presume you have used an ideal spring in your mental maunderings. |
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//whereas the primary purpose of this is to store energy generated while the engine is idling // Not much about conservation of energy in there, is there? Winding up a spring whilst the engine is idling would mean it is not idling (operating under no load), one would assume. |
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//Winding up a spring whilst the engine is idling would
mean it is not idling (operating under no load), one would
assume.// |
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Idle doesn't mean it's operating under no load
whatsoever. Idle is just the speed the engine runs at
when the throttle is closed. In this state, the engine still
has to power the alternator, oil pump, air conditioning,
and so on. And regardless of what it needs to power, it
needs to maintain enough speed to run smoothly, even
when there's not much load on it. There's still enough
leftover torque produced by the engine in this state to
move the vehicle, albeit very slowly. In the case of a
manual transmission, you decouple the engine from the
transmission by use of the clutch, so that torque
effectively goes to waste. With an automatic
transmission, that extra power is simply used to slosh
transmission fluid around inside the torque converter,
since the output shaft of the torque converter is locked
by the brakes. In either case, the engine needs to be
producing enough torque at any given time to start
moving the vehicle immediately, but until the vehicle is
actually requested to start moving, that torque could be
used to drive something else rather than simply being
thrown away. |
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But regardless, the point of this isn't necessarily to use
less energy overall. Rather, it's to produce more peak
torque for a short time than would normally be available
from the engine alone. To that end, a spring of any size
made of any sort of material would provide at least SOME
benefit, and to improve that benefit you would only have
to find the optimum material/size/cost tradeoff for
however much extra torque you want to be able to
produce and for how long you want your reserve to last. |
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