Electrical Engineering Question about EV long range development
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From: Raleigh
Electrical Engineering Question about EV long range development
I was thinking about regenerative power on the way to work. I know this sounds simple, and by no means am I an electrical engineer, but why the hell havent they used the axles as gears and attach alternators to each axle? Once you get the car rolling it should be able to generate enough power to go as far as you want.
Looks like someone already applied for the patent
http://www.invention.net/sellers.htm
Looks like someone already applied for the patent
http://www.invention.net/sellers.htm
Joined: Oct 2003
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From: MAHT-O-MEDI
You still have wind resistance and friction, both in the alternators themselves but the tire contact patch. It is not outer space.
There have been electric car designs with in wheel motors that sort of do what you are talking about but that has not caught on with the big automakers for whatever reason.
Joined: Oct 2003
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From: MAHT-O-MEDI
Dunno, maybe adding the weight, cost and drag of four alternators does not add the benefit you are estimating and regenerative braking ends up being easier/more reliable/efficient in the end.
But I am pretty much a financial analyst, so what do I know?
Joined: May 2002
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You have a couple of issues with this idea. The simple answer is that you can't generate more power than you've put in. You seem to think that once the car is rolling, it'll generate its own forward motion by these axle motors. That's patently untrue unless you travel downhill in all directions. Simple physics says that power out < power in, every time. Otherwise, you'd have perpetual motion and you'd be getting out more energy than you're putting in (physically impossible).
1. Axles change angles as the suspension moves, which means the belt is rarely perpendicular to the axle. You'll have to design a system that is reliable but flexible. That's bad for efficiency as the more rigid it is, the more efficient it is (generally speaking). In-line motors would be interesting but require a dual-shaft design with some sort of gear system from the axle to the input of the motor. You'll also add unsprung weight to the axles (bad).
2. Space - you don't have a ton of room for this in the front (or back) of a car.
3. Once the car is rolling, you need to keep it rolling. Using the car to generate power from the axles means you're adding constant drag (unless you uncouple the motors when accelerating). You will get out less power than you put in, so it's still kind of pointless. You're using up energy that should be pushing the car forward, not generating power to....push the car forward, but with a reduction due to inefficiences.
4. Protecting the components is difficult at the axles. Simple covers/shields will not suffice, especially in challenging environments. Think about the belts on your car - they last about 100K miles in a relatively protected area with perfectly in-line components. If belts were used (per that link), you'd never be able to get the belts to survive.
There are a lot more issues but those are the first major ones that jumped out at me.
Bottom line: in-line motors with the transmission/engine make more sense for packaging, ability to decouple and also for service/space/packaging issues.
1. Axles change angles as the suspension moves, which means the belt is rarely perpendicular to the axle. You'll have to design a system that is reliable but flexible. That's bad for efficiency as the more rigid it is, the more efficient it is (generally speaking). In-line motors would be interesting but require a dual-shaft design with some sort of gear system from the axle to the input of the motor. You'll also add unsprung weight to the axles (bad).
2. Space - you don't have a ton of room for this in the front (or back) of a car.
3. Once the car is rolling, you need to keep it rolling. Using the car to generate power from the axles means you're adding constant drag (unless you uncouple the motors when accelerating). You will get out less power than you put in, so it's still kind of pointless. You're using up energy that should be pushing the car forward, not generating power to....push the car forward, but with a reduction due to inefficiences.
4. Protecting the components is difficult at the axles. Simple covers/shields will not suffice, especially in challenging environments. Think about the belts on your car - they last about 100K miles in a relatively protected area with perfectly in-line components. If belts were used (per that link), you'd never be able to get the belts to survive.
There are a lot more issues but those are the first major ones that jumped out at me.
Bottom line: in-line motors with the transmission/engine make more sense for packaging, ability to decouple and also for service/space/packaging issues.
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Joined: Jul 2009
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You have a couple of issues with this idea. The simple answer is that you can't generate more power than you've put in. You seem to think that once the car is rolling, it'll generate its own forward motion by these axle motors. That's patently untrue unless you travel downhill in all directions. Simple physics says that power out < power in, every time. Otherwise, you'd have perpetual motion and you'd be getting out more energy than you're putting in (physically impossible).
1. Axles change angles as the suspension moves, which means the belt is rarely perpendicular to the axle. You'll have to design a system that is reliable but flexible. That's bad for efficiency as the more rigid it is, the more efficient it is (generally speaking). In-line motors would be interesting but require a dual-shaft design with some sort of gear system from the axle to the input of the motor. You'll also add unsprung weight to the axles (bad).
2. Space - you don't have a ton of room for this in the front (or back) of a car.
3. Once the car is rolling, you need to keep it rolling. Using the car to generate power from the axles means you're adding constant drag (unless you uncouple the motors when accelerating). You will get out less power than you put in, so it's still kind of pointless. You're using up energy that should be pushing the car forward, not generating power to....push the car forward, but with a reduction due to inefficiences.
4. Protecting the components is difficult at the axles. Simple covers/shields will not suffice, especially in challenging environments. Think about the belts on your car - they last about 100K miles in a relatively protected area with perfectly in-line components. If belts were used (per that link), you'd never be able to get the belts to survive.
There are a lot more issues but those are the first major ones that jumped out at me.
Bottom line: in-line motors with the transmission/engine make more sense for packaging, ability to decouple and also for service/space/packaging issues.
1. Axles change angles as the suspension moves, which means the belt is rarely perpendicular to the axle. You'll have to design a system that is reliable but flexible. That's bad for efficiency as the more rigid it is, the more efficient it is (generally speaking). In-line motors would be interesting but require a dual-shaft design with some sort of gear system from the axle to the input of the motor. You'll also add unsprung weight to the axles (bad).
2. Space - you don't have a ton of room for this in the front (or back) of a car.
3. Once the car is rolling, you need to keep it rolling. Using the car to generate power from the axles means you're adding constant drag (unless you uncouple the motors when accelerating). You will get out less power than you put in, so it's still kind of pointless. You're using up energy that should be pushing the car forward, not generating power to....push the car forward, but with a reduction due to inefficiences.
4. Protecting the components is difficult at the axles. Simple covers/shields will not suffice, especially in challenging environments. Think about the belts on your car - they last about 100K miles in a relatively protected area with perfectly in-line components. If belts were used (per that link), you'd never be able to get the belts to survive.
There are a lot more issues but those are the first major ones that jumped out at me.
Bottom line: in-line motors with the transmission/engine make more sense for packaging, ability to decouple and also for service/space/packaging issues.
OP you cannot defy the laws of physics.
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Joined: Oct 2000
Posts: 15,323
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From: Longmont, CO
I was thinking about regenerative power on the way to work. I know this sounds simple, and by no means am I an electrical engineer, but why the hell havent they used the axles as gears and attach alternators to each axle? Once you get the car rolling it should be able to generate enough power to go as far as you want.
Looks like someone already applied for the patent
http://www.invention.net/sellers.htm
Looks like someone already applied for the patent
http://www.invention.net/sellers.htm
Are you asking why the car couldn't propel itself forward using some means, then generate electricity from the forward motion, which is used again to propel the car forward, generating electricity, propelling the car, etc.?
You're asking to build a perpetual motion machine, or a free energy generator.
Thermodynamics - not just a good idea, it's the law.
It certainly would work if you're just looking for a different way to mount the alternator, as opposed to with the accessory belt of the engine or within the transmission (like IMA does, I think?) But it will not let you go as far as you want.
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From: WA
Alternators use power to generate current... it is going to vary depending upon draw but I think the average power to run a typical automotive alternator is about 2-4 HP... just to run non-locomotive systems, so obviously it is hard to come out ahead. Perpetual motion does not come this way.
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From: MAHT-O-MEDI
1. You'll also add unsprung weight to the axles (bad).
4. Protecting the components is difficult at the axles. Simple covers/shields will not suffice, especially in challenging environments. Think about the belts on your car - they last about 100K miles in a relatively protected area with perfectly in-line components. If belts were used (per that link), you'd never be able to get the belts to survive.
4. Protecting the components is difficult at the axles. Simple covers/shields will not suffice, especially in challenging environments. Think about the belts on your car - they last about 100K miles in a relatively protected area with perfectly in-line components. If belts were used (per that link), you'd never be able to get the belts to survive.
#1 is a why in-wheel motors are a bad idea. Drive a motor scooter with the engine unsprung attached to the swing arm and go over a large bump or pothole. WHAM! Teeth rattling. You can probably tune out some with suspension but heavy components in the wheel make for a VERY rough ride. A 30 pound wheel and tire combo goes over a pothole an entirely different way than an 80 pound one.
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