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Benchwayze

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Isn't it something to do with centrifugal force Roy? Or maybe inertia; or is it momentum? Unless it's an advanced clockwork spring! :lol:

I forget most of the Mechanics I learned at school; although you'll have gathered that!
I would imagine that whatever savings they do manage, won't be passed on in reduced fares! More likely we will have to pay for the experimental technology!

8)
 

marcros

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i would think that it is the potential energy and momentum. The heavy old flywheel has the momentum to continue due to its weight. The new one makes up for the lack of weight by spinning faster. much the same as a heavy car breaking hard, verses a lighter car travelling faster breaking to stop.
 

Digit

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Yes, quite gentlemen, but how to use it?
To accelerate a bus and passengers to a given speed in a given time takes a certain amount of energy, spinning up the flywheel would require additional energy, ie, fuel.
If it's de-clutched during acceleration and engaged during deceleration, most busses have pre-selector boxes IME, that would spin it up and also decrease breaking distance.
Then it could be re-engaged as the bus pulls away, that would save fuel, but it's begining to sound pretty complex now.
The down side of any large amount of energy stored in flywheels is the gyroscopic effect, they won't go round corners! :lol:

Roy.
 

MickCheese

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Don't think busses are pre select any more, they are automatic.

The article doesn't give much info. I could understand if we were talking about electric vehicles with storage batteries but I don't see how you can store energy for a combustion engine.

Mick
 

monkeybiter

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Digit":3hcxm7p4 said:
The down side of any large amount of energy stored in flywheels is the gyroscopic effect, they won't go round corners! :lol:
Roy.
That would depend on the axis of rotation. Vertical would solve the resistance to cornering, but then with a small diameter [and higher speed] I don't think the resistance to turning would be significant.
 

Digit

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Mick, if used as I suggested the energy doesn't come from the engine, it would come from deceleration, using the energy from the IC engine to spin it up would increase fuel consumption.

Vertical rotation east/west or north/south? The idea was tried years ago by CalTech? They stated that you could spin it up at home, drive to the nerest airport and take a 6 month holiday and when you returned there would still be sufficient energy to get you home, provided it was a straight line! :lol:
Vertical N/S, along the axis of the vehical, assuming a fixed gimbal, should result it movement to the left when a force is applied to the right, surely?
ie, Sopwith Camel, bike wheel?
The amount of energy must be a factor of speed and mass, a large dia, slow flywheel storing the same energy as a small dia one at high speed. But there will be difference in flywheel acceleration/deceleration in the same way that a heavy rimmed flywheel produces more torque than a heavy centered one does.

Roy.
 

AndyT

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My understanding of the benefit would be this:

Current system: bus going along, needs to stop - all of its kinetic energy is converted to heat (in the brakes) and is lost to the surroundings. That loss has to be made up, by burning diesel in the engine, to get more kinetic energy and get the bus moving.

New system: bus going along, needs to stop - some of its kinetic energy is transferred to the flywheel - which was static but now gets spun up as the bus slows down. Energy is retained in the system, since the flywheel continues to spin while the bus is at rest.

The gyroscope effect does not matter, as the bus always moves off from rest by going forward - by the time it is doing much turning, the flywheel will have transferred its energy to the bus and be at rest.

It sounds a really clever idea.

There was, briefly, a demonstrator flywheel bus beside the Bristol docks which just went up and down a short stretch in a straight line. This sounds much better.

I believe there are other systems of regenerative braking which store energy by compressing a gas - but I don't know if there are any in commercial use.
 

Digit

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That's how I see it Andy, but the coupling/decoupling must be interesting, without a fluid coupling the load on shafts will be high, also, as I suggested, braking distance should be less with less wear on the brakes etc.
One of the factors inherent in the fuel saving, as I see it, is distance between stops, the greater the number of stops in any distance the greater the savings.
Could be advantageous on many urban streets, not only for buses either. It'll be interesting to see how the tests proceed.
I take your point about the flywheel having wound down as the bus pulls away as well.

Roy.
 

Benchwayze

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monkeybiter":39wle4q3 said:
Digit":39wle4q3 said:
The down side of any large amount of energy stored in flywheels is the gyroscopic effect, they won't go round corners! :lol:
Roy.
That would depend on the axis of rotation. Vertical would solve the resistance to cornering, but then with a small diameter [and higher speed] I don't think the resistance to turning would be significant.
Precession won't allow a gyro to tip. If it did, it would be useless as a compass, and in any case the gyro doesn't control the energy that spins it, so I'm not sure it's the same thing as a flywheel storing energy, or imparting momentum. :?:
 

Digit

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The example I quoted from CalTech John was with the flywheel providing the only drive to the wheels. A gyroscope, without a cage that is, is a heavy rimmed flywheel.
If you attempt to turn a bike left by pulling on the LH handle bar the bike will turn right.
You have to 'topple' the gyroscope by leaning it to the left first.
A push bike wheel mounted on a shaft with a handle on each side that is spun up to high speed with you holding each handle can not be deviated from its course by you, such is its inertia.
A heavy rimmed flywheel provides greater torque as a driver by virtue of the old statement that work done is force times distance, thus a heavy rimmed flywheel, (gyroscope) does not need to be solid, it works just as well with spokes.


Roy.
 

Benchwayze

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Digit":10irlj2f said:
The example I quoted from CalTech John was with the flywheel providing the only drive to the wheels. A gyroscope, without a cage that is, is a heavy rimmed flywheel.
If you attempt to turn a bike left by pulling on the LH handle bar the bike will turn right.
You have to 'topple' the gyroscope by leaning it to the left first.
A push bike wheel mounted on a shaft with a handle on each side that is spun up to high speed with you holding each handle can not be deviated from its course by you, such is its inertia.
A heavy rimmed flywheel provides greater torque as a driver by virtue of the old statement that work done is force times distance, thus a heavy rimmed flywheel, (gyroscope) does not need to be solid, it works just as well with spokes.


Roy.
The most handy demonstration of precession (anti-toppling) we woodworkers have is the router.
Start it up, (No cutter required!!! 8) ) and holding tight, tip the router one way or the other. You immediately notice the effect of precession. It can be disconcerting the first time you experience it by accident... :D

Oh! yes... The last time I experienced precession on a Motor Cycle, was when it saved my life; by allowing me to lean the bike right over and accelerate out of the path of an artic, a position, I had stupidly put myself in by entering a bend too close to the white line! I found out what it meant for the 'blood to run cold'. Most motorcyclists will have experienced the feeling I'm sure. :mrgreen:
 
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