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jmead

Electric 240z Project Pics

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Regenerative braking is a form of kinetic energy recovery, so let's make sure not to get our terms crossed or anything. They're very much related and/or the same in many ways, not separate ways to do the same thing.

 

jmead in his project process talks about how the motor/controller combo he chose to go with wouldn't be able to perform regenerative braking, mostly due to the cost of such systems.

 

Many of the hybrids and most of the expensive electric cars have regenerative braking which does help considerably. This is purely my opinion, but I believe this is the #1 reason hybrid's actually get better mpg. Hybrid's get what seems to me the same MPG on strictly highway use than the same car would get with the same gasoline engine it already has, while in city it's significantly better. In city the hybrid can get off the line in electric mode which is where gasoline engines suck back the fuel, and then once you're going the gasoline engine can take over. During braking much of the energy it took to get off the line in the first place is put back into the system via regenerative braking.

 

This is a very crucial system for hybrids because you can't expect the gasoline engine to create a charge and get more than 100% of that energy back, meaning that if it's taking 10hp to keep the car going, and then you tack on another 10hp for battery regeneration giving a total load of 20hp, you're not going to get more than 10hp back for an equal length of time, that would be called perpetual energy which is something we have yet to invent.

 

What I'm getting at is that any way you look at it, is that what you're talking about KROz is already being done, and done very well I might ad. You're only ever going to be able to make a car go so much farther with techniques like this because there is always going to be waste energy in a car somewhere or another. The main thing we could do to improve the existing system would be to half rolling resistance without loosing grip on the road. This would allow less energy to keep the car going and thus more of the energy put into getting the car started would keep it going at a desired speed.

 

This is also why MPG freaks run their tires at max PSI, to the point of danger in some cases. The higher PSI lowers rolling resistance, but also reduces considerable grip in most cases. To be fair though, running higher psi levels than most people do can be much safer in rainy conditions because the tire cuts through the water better making it less likely to hydroplane.

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[quote name=

For sake of simplicity' date=' the farthest you could remove the stock drivetrain would be to cut out and reshape the floor right in front of the diff and mount the motor directly to the diff, allowing removal of the driveshaft and transmission. The only concern here is that you need to make sure you're not going to overheat the motor at lower speeds, and not go beyond it's RPM limits at higher speeds. A larger motor is less likely to overheat, but of course it's larger and harder to fit into the space requirements without impeding upon the passengers.

 

[/quote]

 

Seems to me that spinning the diff around and putting the motor where the gas tank was would be the better route. This would be both easier to cool and help offset the weight of the batteries in front.

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Seems to me that spinning the diff around and putting the motor where the gas tank was would be the better route. This would be both easier to cool and help offset the weight of the batteries in front.

 

Why didn't I think of that? Not a bad idea actually in my opinion.

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The motor could be mounted above the diff parralel to it and bolted to the existing holes/studs in the diff itself. The drive could be a timing type belt similar to the Harley. This way the whole drive would move together and be isolated from the car. Number of teeth in the pulleys could be varied to determine the final drive ratio.

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awd transmission? why even bother for a transmission at all? The e-motor has full torque from rpm=0 until full rpm. That is why you could put an e-motor on every wheel. Despite of the post I read about two e-motors on let's say your frontwheels would act like a welded axel.. That aint the case because the e-motor will always have it's tolerance in the rpm due the curve that you make. And if you even worry about that, why not put a controller in that keeps tracks of the angle your frontwheel make (to turn) and let it adjust the rpm of the inner-curve wheels with regard to the outher ones.

 

Electronics have no limits, it's just how we use them :-)

 

Marcel

hobbyguy (in electronics & metalworking)

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awd transmission? why even bother for a transmission at all? The e-motor has full torque from rpm=0 until full rpm. That is why you could put an e-motor on every wheel. Despite of the post I read about two e-motors on let's say your frontwheels would act like a welded axel.. That aint the case because the e-motor will always have it's tolerance in the rpm due the curve that you make. And if you even worry about that, why not put a controller in that keeps tracks of the angle your frontwheel make (to turn) and let it adjust the rpm of the inner-curve wheels with regard to the outher ones.

 

Electronics have no limits, it's just how we use them :-)

 

Marcel

hobbyguy (in electronics & metalworking)

 

Which is why I stated that would only be an issue if you were using a SINGLE motor without a diff, a motor that had two opposing outputs on a singular motor.

 

Why do this? Because mounting motors at each wheel WILL add an insane amount of unsprung mass that SHOULD be avoided at all costs for anyone making a performance oriented (even mildly) project. You "could" use 4 smaller motors mounted to the chassis with axles running to each wheel, but at that point you have to as why. You have a perfectly good diff sitting in a RWD car, why not use it? Sure you CAN use an electric engine with direct drive thanks to it's instant torque output, but you must also remember that the heat and load generated from doing that is great and should be considered. Even an electric motor likes a torque multiplier.

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Already been sold.

 

Now I'm working on a 52 Ford F-1 and a 76 280z that will put the 240z to shame. (800 ft-lbs vs 250, 300lbs of LiFePO4 vs 700lbs of lead, etc). Updates will follow when I've got more to show.

 

Ultimately I want to start building cars for people, so if you're serious PM me and we'll talk. :)

 

 

I'd like to see the 52 F-1, i've got a 50.

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The 52 is quite nice. My family has as flatbed model with a winch right behind the cab run off the PTO. I swear that old 1bbl flathead v8 is the most reliable thing on the farm, still a working truck.

 

jmead - are you using an AC or DC motor for the build?

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