# Fuel Savings from Roadbed Electrification Pays for the Power Plant In 14 Months

That what I said when he said circular furrows were impossible.

John Fields has an IQ of 14.
His case worker keeps him posting here to keep him off the street.
Bret Cahill
Well, he did say he was asking and said he wasn't versed, so I went gentle .
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On Fri, 5 Jun 2009 20:48:33 -0700 (PDT), Bret Cahill

--
Considering the number of times I've skewered you, then, that puts you
at about a solid 4, yes?
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On Sat, 6 Jun 2009 03:47:58 +0100, "Androcles"

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My point exactly, which was directed at the "But they do not."

[have as much 'stopping potential' as they have starting potential]
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wrote:

Let us assume we apply a low voltage to an unloaded DC motor and it takes 10 seconds to accelerate to 1000 RPM, overcoming inertia (or we could just load it with a heavy flywheel or propel a train). Force = mass * acceleration. With a higher voltage we can reach 1000 RPM in 5 seconds, we've increased the force so we increase the acceleration. Now we disconnect the supply and short the terminals on the motor. It grunts and stops in a few milliseconds no matter what voltage we used to accelerate it. All the kinetic energy of the flywheel or train is dissipated in the windings which heat up rapidly. deceleration = -Force/mass. Therefore they have MORE stopping potential than starting potential.
Incidentally, I've actually done this with a tapping machine that was snapping taps as it cut threads and bottomed in a blind hole. The usual solution is to break torque mechanically, but I tripped the breaker on increased current as the motor slowed and shorted the motor with normally closed contacts on the breaker. That was many years ago.
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On Sat, 6 Jun 2009 19:04:11 +0100, "Androcles"

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I've done the same thing on an orbital welder in order to make sure the
weld head is indexed properly at the end of a weld, but let's go back
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wrote:

You asked: "If the input to a DC motor is shorted, once it's running, why would it take longer to stop it ... yada yada yada (impedance)"
That, to me, means that you thought a motor can't be stopped in less time than it took to run it up.
I said "Huh?" because it will NOT take longer to stop it.
What's up with that?
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On Sat, 06 Jun 2009 17:38:55 -0500, John Fields wrote:

Some of the confusion may be due to the original claim of regenerative braking. If you actively reverse current to the motors, you should produce the same torque either direction, but at the cost of consuming battery power.
Recovery of the decel energy requires some non-trivial impedance matching to put it back into the battery, and would decrease in efficiency as the velocity decreased, I would think. At zero, there would be no retarding force.
IMHO, regenerative braking is a good idea, but it's not reliable enough to be the primary braking system, because of its dependence on the electronic controller. Initial brake pedal force should invoke regeneration, but should be backed up by reliable hydraulic brakes past a threshold force indicating driver dissatisfaction with current stopping performance.
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The is how Americans stop trains: http://www.railway-technical.com/brake2.shtml#DynamicBrakes
Typically American, the energy as wasted as heat.
This is a British train:
http://ro.altermedia.info/images/eurostar-chunnel-train-4.jpg
Overhead is a catenary. It has a high voltage.
IYHO, regenerative braking is a good idea. It's not your idea though.
What do you not think stops the Eurostar?
Your opinion, however honest it may be, is about as useful as a tit on a bull.
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On Sun, 07 Jun 2009 04:56:03 +0100, Androcles wrote:

Too bad you are so pathetic you need to snip context to appear to have a point. But I'll give you a sorely needed clue - most people see right through your dishonest tactic. I won't even bother to repost, I'll just mention that the original subject was regenerative braking on automobiles, and I was clearing up some confusion on the issue.
Trains were not at issue.
You are a disgrace to the good name of J. K. Rowling. Shame.
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Bill Ward wrote:

Billowbwap: are you now bothering people in newsgroups other than alt.global-warming after we successfully scared you away?
Hint: Bill needs the treatment, I mean THE treatment, where you confront him with the facts.
Q
--
Ultimately to survive we should blow up our Moon, the particles
in orbit that remain help to combat global warming.
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Actually the original subject was Fuel Savings from Roadbed Electrification, I'm so glad you've cleared up that confusion.

What do you not think stops the Eurostar? (Ward's answer is a blank stare, not even a dropped jaw)
Fuck off, your miserable opinion is about as useful as a pitot tube on a snail.
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That's nothing.
You ought to see them water the banks of the freeway in the middle of a "state of emergency" drought.
We might not have water to flush the toilet but, by golly, we're going to look at something greener than brittle bush when we drive to work.
Bret Cahill
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That's nothing.
You ought to see them water the banks of the freeway in the middle of a "state of emergency" drought.
We might not have water to flush the toilet but, by golly, we're going to look at something greener than brittle bush when we drive to work.
Bret Cahill =========================================Well, to be fair, American rail is not extensively electrified as it is here so the energy has to be dumped somehow, but that's no excuse for Ward's ignorant bigotry. That he imagines he can limit the debate on energy efficiency referred to in the thread title to road vehicles demonstrates the very narrow-mindedness he accuses others of.
He claims to have designed control systems and drivers for stepper motors but hasn't ever seen one used for vehicle propulsion or regeneration, and also claims "regenerative braking is a good idea, but it's not reliable enough to be the primary braking system, because of its dependence on the electronic controller."
If he really was as capable as he boasts he'd design a controller for a car. The guy is not even a decent devil's advocate pointing out what the problems might be, he's an opinionated fuckwit still living in the 20th century.
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In most places that is non-potable grey water from waste water with the nasty stuff removed.
By using it to irrigate, it trickles down to the water table getting cleaned by nature for free on the way.
You really don't know how much of anything in the real world works, do you?
--
Jim Pennino

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wrote:

Ok, now I can see that you actually don't get what I am saying. By reverse, I don't mean "reverse the function so the motor becomes a generator". I mean "reverse the direction that the motor is trying to turn", which will actually *use* battery juice that is already stored.
Remember, the original question was whether you can bring the car to a complete stop using only electricity and no mechanical brakes. The answer is yes.
You are correct that it is not a simple 1:1 relationship in a practical sense to stop the car with the generator effect. The most obvious reason is that you usually would like to stop faster than you have accelerated to the current speed, and you may be going downhill as well. This means that even if you 'short' the motor<>generator as someone suggested, the kinetic energy of the car will be have to be dissipated as heat at a rate that will prevent damage to the motor.
I am suggesting that there will be a combination of effects used to provide the system load, and that over time, it will develop into a mostly electric system which gives ABS, and mechanical brakes will be a back-up component and for parking. Right now, it isn't even legal to have a car without mechanical brakes, no matter how reliable electric braking could be made, so the argument is purely academic.
-tg
'Don't worry about people stealing your ideas. If your ideas are any good, you'll have to ram them down people's throats.' - Howard Aiken

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