My Electric Car thread!
Discussion
Max_Torque said:
Globs said:
Simples. One engine+gen, two black boxes, one set of drive motors and a few wires.
No gearbox, diff, driveshafts, alternator etc required.
wow, you should make one of those if it is that easier. I mean, Toyota spend ~£2B on the prius and GM spent a piffling ~£3.5B on the Volt. What a bunch of idiots !No gearbox, diff, driveshafts, alternator etc required.
And electric doesn't need gearboxes or driveshafts - it all depends upon the design. The simplest would have a multi-pole motor on each hub. If you ignore unsprung weight no driveshafts are needed.
The beauty of electric is that you can control your torque and speed, so you can build wheel speed motors. They may not be the cheapest or best, but it's quite possible. Just browse any supplier of brushless motors to see the variety of speeds and torques available.
If you decide on a fast motor you'll have to gear it down won't you?
Max_Torque said:
(PS, anyone who says "it's electric so it doesn't need a gearbox or driveshafts" might want to reconsider exactly how silly that statement is.......... )
You need to tell these guys - not me!http://www.e-traction.com/TheWheel.htm
Silly people.
Edited by Globs on Thursday 22 December 18:48
Name me a production wheel motor?
Lots (and lots and lots and lots) of people / companies have pushed round lots (and lots and lots and lots) of designs (virtual and some times prototype) for wheel/hub motors. All of them fall over on exactly the same things that makes an ICE engine require a gearbox (and that is that peak power is generated at fixed speed) (ok, you can use field weakening to extend the constant speed region, but peak power is still at one single speed)
Hence, if you wind your motor to produce high torque at low speed (high turn count) then you find that the maximum speed (and hence power) is low. Or you wind your motor with a low torque wind (lower turn count) but then you have a poor low speed torque output.
Anyone who says "an electric motor doesn't require a multispeed gearbox on vehicular traction application" simply doens't understand how an electric motor works. (and it's not just the motor, take the power inverter, its costs are directly linked to peak current (which is proportional to peak torque) it's losses are also linked to the square of that current, And whilst an electric motor can theoretically make peak torque at zero speed, the power electronics driving it can't.
And that's before we get to the issues of unsprund mass and where to put the friction brake system etc, let alone the sealing and durability (hint, think about the vibration environment of an unsprung heavy motor in a wheel) requirements, and of course the thermal management requirements.
No, it's very easy to say "wheel motors are the answer" and a whole lot harder to actually make one that is practical and affordable!
Lots (and lots and lots and lots) of people / companies have pushed round lots (and lots and lots and lots) of designs (virtual and some times prototype) for wheel/hub motors. All of them fall over on exactly the same things that makes an ICE engine require a gearbox (and that is that peak power is generated at fixed speed) (ok, you can use field weakening to extend the constant speed region, but peak power is still at one single speed)
Hence, if you wind your motor to produce high torque at low speed (high turn count) then you find that the maximum speed (and hence power) is low. Or you wind your motor with a low torque wind (lower turn count) but then you have a poor low speed torque output.
Anyone who says "an electric motor doesn't require a multispeed gearbox on vehicular traction application" simply doens't understand how an electric motor works. (and it's not just the motor, take the power inverter, its costs are directly linked to peak current (which is proportional to peak torque) it's losses are also linked to the square of that current, And whilst an electric motor can theoretically make peak torque at zero speed, the power electronics driving it can't.
And that's before we get to the issues of unsprund mass and where to put the friction brake system etc, let alone the sealing and durability (hint, think about the vibration environment of an unsprung heavy motor in a wheel) requirements, and of course the thermal management requirements.
No, it's very easy to say "wheel motors are the answer" and a whole lot harder to actually make one that is practical and affordable!
Globs said:
it's efficiency
So lets do some sums on a series hybrid:lets say we have a roadload of 5kW.
Because runing our ICE engine at only 5kW would not enable it to run without signficant pumping losses, we have to run our ICE at full load, charge a battery, then use that battery to turn the wheels via atraction motor.
Unfortunately, that means the power has to go:
Fuel - heat - pressure - reciprocating mech power - rotating mech power - 3ph AC electricity (generator) -power inverter (to DC) - DC electricity - chemical energy in battery - DC electricity - power inverter (to AC)- 3ph AC into traction motor - rotational mech power - mech link to wheel - tractive effort.
(phew, that was some trip!) And every stage has a loss associated with it. In fact, for any current practical system, the roundtrip total efficiency will be hovering arounf 60% at best. Now when running your ICE at its optimum efficiency zone only nets you approx 12% efficiency improvement, throwing away 40% of your total energy generated is not a smart move!
The simple fact of the matter is that currently, pure series hybrids cannot outperform the best conventional ICE powertrains that cost something like 50% of the cost.
Max_Torque said:
Anyone who says "an electric motor doesn't require a multispeed gearbox on vehicular traction application" simply doens't understand how an electric motor works. (and it's not just the motor, take the power inverter, its costs are directly linked to peak current (which is proportional to peak torque) it's losses are also linked to the square of that current, And whilst an electric motor can theoretically make peak torque at zero speed, the power electronics driving it can't.
The Tesla roadster doesn't have a multispeed gearbox.Perhaps they don't understand either?
Most of the time speed for an electric motor depends upon timing, which can be varied as required by the drive electronics.
So just design the motor for max speed and use the electronics for the low power low speed part.
Globs said:
Max_Torque said:
Anyone who says "an electric motor doesn't require a multispeed gearbox on vehicular traction application" simply doens't understand how an electric motor works. (and it's not just the motor, take the power inverter, its costs are directly linked to peak current (which is proportional to peak torque) it's losses are also linked to the square of that current, And whilst an electric motor can theoretically make peak torque at zero speed, the power electronics driving it can't.
The Tesla roadster doesn't have a multispeed gearbox.Perhaps they don't understand either?
Most of the time speed for an electric motor depends upon timing, which can be varied as required by the drive electronics.
So just design the motor for max speed and use the electronics for the low power low speed part.
As i mentioned, the cost of the power electronics is driven by the peak current requirement (proportional to torque) rather than the peak power requirement (also to a large degree in the actual Emachine & energy storage systems themselves). Without a gearbox, deliverying a large peak torque at the wheels involves massive expense in the power electronics/batteries and motors, landing you with a large weight/cost and efficiency penalty.
Also, an electric motor depends upon "timing" the entire time. This is the problem with electric cars, because people had a toy RC one as a kid everyone says "they are simple" or "just" do so and so etc. If i asked you "could you design and build an IC engine" then i would expect you to say no, but once someones read a few lines on the net about electric motors and drive electronics they seem to think it is an equally easy task to design and build one. Well, here'e a heads up, ITS NOT !!
The typical control system will be looking at the rotor position 20 thousand times a second, simultaneously measuring the phase currents at the same moment, then converting (using the park-clarke transform) the rotating 3 phase, 120deg out of phase aligned, magnetic field in to a 2 axis orthangonal system (d & q), applying closed loop current controllers to each demand, using a maximum modulation index parameter to determine when the maximum system appyable voltage is reached and field weakening might be required, and finally taking previously calibrated mapping data (voltage, temps, speed etc) to work out the torque characteristic Ki (in Nm/Ampere) to deliver the requested torque demand. But as you say, that's just the "simple" stuff
Max_Torque said:
If i asked you "could you design and build an IC engine" then i would expect you to say no,
But I would say yes, they are also fairly well understood.Max_Torque said:
The typical control system will be looking at the rotor position 20 thousand times a second, simultaneously measuring the phase currents at the same moment, then converting (using the park-clarke transform) the rotating 3 phase, 120deg out of phase aligned, magnetic field in to a 2 axis orthangonal system (d & q), applying closed loop current controllers to each demand, using a maximum modulation index parameter to determine when the maximum system appyable voltage is reached and field weakening might be required, and finally taking previously calibrated mapping data (voltage, temps, speed etc) to work out the torque characteristic Ki (in Nm/Ampere) to deliver the requested torque demand. But as you say, that's just the "simple" stuff
Actually all of the modern brushless motors used in the model world use this exact method of three phase drive (without optical feedback even). You can buy small ones for about $8..Brushless ESC
I know you get problems as you scale up, but the three phase motor speed control has been understood and commoditised for some time now - models need efficiency gains too
Max_Torque said:
Name me a production wheel motor?
Lots (and lots and lots and lots) of people / companies have pushed round lots (and lots and lots and lots) of designs (virtual and some times prototype) for wheel/hub motors. All of them fall over on exactly the same things that makes an ICE engine require a gearbox (and that is that peak power is generated at fixed speed) (ok, you can use field weakening to extend the constant speed region, but peak power is still at one single speed)
Hence, if you wind your motor to produce high torque at low speed (high turn count) then you find that the maximum speed (and hence power) is low. Or you wind your motor with a low torque wind (lower turn count) but then you have a poor low speed torque output.
Anyone who says "an electric motor doesn't require a multispeed gearbox on vehicular traction application" simply doens't understand how an electric motor works. (and it's not just the motor, take the power inverter, its costs are directly linked to peak current (which is proportional to peak torque) it's losses are also linked to the square of that current, And whilst an electric motor can theoretically make peak torque at zero speed, the power electronics driving it can't.
And that's before we get to the issues of unsprund mass and where to put the friction brake system etc, let alone the sealing and durability (hint, think about the vibration environment of an unsprung heavy motor in a wheel) requirements, and of course the thermal management requirements.
No, it's very easy to say "wheel motors are the answer" and a whole lot harder to actually make one that is practical and affordable!
You certainly seem knowledgeable on the subject so genuine question here. Are these lot selling snake oil or is it a viable design?. Lots (and lots and lots and lots) of people / companies have pushed round lots (and lots and lots and lots) of designs (virtual and some times prototype) for wheel/hub motors. All of them fall over on exactly the same things that makes an ICE engine require a gearbox (and that is that peak power is generated at fixed speed) (ok, you can use field weakening to extend the constant speed region, but peak power is still at one single speed)
Hence, if you wind your motor to produce high torque at low speed (high turn count) then you find that the maximum speed (and hence power) is low. Or you wind your motor with a low torque wind (lower turn count) but then you have a poor low speed torque output.
Anyone who says "an electric motor doesn't require a multispeed gearbox on vehicular traction application" simply doens't understand how an electric motor works. (and it's not just the motor, take the power inverter, its costs are directly linked to peak current (which is proportional to peak torque) it's losses are also linked to the square of that current, And whilst an electric motor can theoretically make peak torque at zero speed, the power electronics driving it can't.
And that's before we get to the issues of unsprund mass and where to put the friction brake system etc, let alone the sealing and durability (hint, think about the vibration environment of an unsprung heavy motor in a wheel) requirements, and of course the thermal management requirements.
No, it's very easy to say "wheel motors are the answer" and a whole lot harder to actually make one that is practical and affordable!
http://www.proteanelectric.com/
It certainly does look impressive and I don't mind confessing to ignorance in thinking that this is how the current crop of EVs were powered. Didn't realize they ran through gearboxes.
redtwin said:
You certainly seem knowledgeable on the subject so genuine question here. Are these lot selling snake oil or is it a viable design?.
http://www.proteanelectric.com/
It certainly does look impressive and I don't mind confessing to ignorance in thinking that this is how the current crop of EVs were powered. Didn't realize they ran through gearboxes.
It's not snake oil, it's just a particular path that has advantages but significant implementation problems. This company thinks they can overcome these problems, most people think the problems are either insurmountable or that the advantages will never be enough to justify furthering it.http://www.proteanelectric.com/
It certainly does look impressive and I don't mind confessing to ignorance in thinking that this is how the current crop of EVs were powered. Didn't realize they ran through gearboxes.
vladcjelli said:
As a complete layman, I always assumed some kind of CVT would be ideal for electric cars.
Please tell me why not, every day's a school day after all.
Most of the current crop of hybrids use CVT's, although they are epicyclic transmissions that effectively sandwich the ratio between two electric motors, and the output ratio can be modified by changing the speed of each motor. That way you can arrange to have a more optimum motor speed across a wider range of road speeds. Prius and Volt work like this, because they also have to couple an IC engine into the mix. Pure EV's tend to have simple 1 or 2 speed transmissions, mainly from a cost optimisation point of view. But these bring the obvious limitations of gradeability, GVW capability and motor efficiency (iron losses) at high speed.Please tell me why not, every day's a school day after all.
No apologies for bumping this interesting thread. I'm sure we'd all be interested to hear how you have both been getting on with the iOn and Leaf now temperatures have taken a proper plunge. How have you been finding range has been holding up compared with the comparatively balmy temperatures of a few weeks ago? TIA.
I'm still here!
I haven't really noticed a massive drop in range to be honest, but I never really test the range limits. It tends to get a top-up charge as soon as I get to work so it rarely has to go more more than 40 miles between charges (work - home - work). Having said this, I dont think we have had more than 3 or 4 degrees below. At minus 15, it might be a different story!
I try and keep the heater off to preserve power, so it is usually a cold place to sit. I'm so glad I got a nice warm down jacket for Christmas! A few days ago, I was forced to keep the heater on, as ice was forming on the windscreen mid journey!
(I'm glad I didn't have it during all the snow last winter!)
Still no major complaints and I'm really glad I am taking part in the trial.
I haven't really noticed a massive drop in range to be honest, but I never really test the range limits. It tends to get a top-up charge as soon as I get to work so it rarely has to go more more than 40 miles between charges (work - home - work). Having said this, I dont think we have had more than 3 or 4 degrees below. At minus 15, it might be a different story!
I try and keep the heater off to preserve power, so it is usually a cold place to sit. I'm so glad I got a nice warm down jacket for Christmas! A few days ago, I was forced to keep the heater on, as ice was forming on the windscreen mid journey!
(I'm glad I didn't have it during all the snow last winter!)
Still no major complaints and I'm really glad I am taking part in the trial.
Edited by FreeLitres on Saturday 11th February 19:49
To OP please do keep updating this thread. It will be very interesting to see someone who has been driving proper cars - X-type and TVR to see how they get on. I assume you will be driving this electric thing properly, e.g. if you need you get somewhere fast you will put your foot down and also will try to have as much fun driving as possible.
Thanks MrCheese,
To be honest, there hasn't been much to report as its very much been "business as usual". At the start of the trial I was convinced that I would run out of juice at least once. I haven't really got close to doing so yet. [TOUCH WOOD!!]
I would say that if I do want to push the car a bit harder, it tends to be in a "point and squirt" stylee. I have found that if you try to press on around corners or roundabouts, you can feel those skinny front tyres start to slide and the car just understeers wide. Even if you had more grip, you sit so high that it would feel a bit unstable if you fling it around corners.
It is always fun to give it some welly off the lights though
. It's nice knowing that the "fuel" for the car will cost me £10 a month regardless of me driving in Eco mode or absolutely flat out. I wish the same was true for the TVR!
To be honest, there hasn't been much to report as its very much been "business as usual". At the start of the trial I was convinced that I would run out of juice at least once. I haven't really got close to doing so yet. [TOUCH WOOD!!]
I would say that if I do want to push the car a bit harder, it tends to be in a "point and squirt" stylee. I have found that if you try to press on around corners or roundabouts, you can feel those skinny front tyres start to slide and the car just understeers wide. Even if you had more grip, you sit so high that it would feel a bit unstable if you fling it around corners.
It is always fun to give it some welly off the lights though
. It's nice knowing that the "fuel" for the car will cost me £10 a month regardless of me driving in Eco mode or absolutely flat out. I wish the same was true for the TVR!Really interesting post OP! (And pure comedy in parts!)
The governments are driving the whole EV revolution, so it's definitely happening!
Interestingly some real petrol heads are changing direction and loving EVs.
Quentin Willson is a prime example, this is a great YouTube of the results of a 12 mth Mitsubishi i-MiEV trial amongst many different types of drviers;
http://www.youtube.com/watch?v=Erg_D1O_ARs
I know Quentin is a true convert and has a Citroen C Zero he drives every day
There are another 33 EV makes coming to the UK market over the next couple of years, from Rolls Royce Phantoms and Range Rovers to Deloreans, and happily "normal looking" Vauxhalls, Volkswagens, Audis and BMWs. They're coming!!
The governments are driving the whole EV revolution, so it's definitely happening!
Interestingly some real petrol heads are changing direction and loving EVs.
Quentin Willson is a prime example, this is a great YouTube of the results of a 12 mth Mitsubishi i-MiEV trial amongst many different types of drviers;
http://www.youtube.com/watch?v=Erg_D1O_ARs
I know Quentin is a true convert and has a Citroen C Zero he drives every day
There are another 33 EV makes coming to the UK market over the next couple of years, from Rolls Royce Phantoms and Range Rovers to Deloreans, and happily "normal looking" Vauxhalls, Volkswagens, Audis and BMWs. They're coming!!
Gassing Station | Readers' Cars | Top of Page | What's New | My Stuff