EV transmissions and Popular Science

[flathill]

Formula E went with a multispeed for a good reason

Sound FX

It is more exciting to hear a vehicle shift. Even I cannot deny that.

I would rather there be a spec battery and then the rest be unlimited

Except a minimum weight to keep costs down

It will be exciting to see direct drive vs geared motors race

In the early days of electric racing I expect efficiency to be the pièce de résistance and single speeds will win, but as wireless charging comes into play along with next gen batteries all out performance is what will win races...in that situation you could see 2 and 3 speed cars, or more likely magnetic cvt's (built into "direct drive" motors) with N120 magnets

 

[liveforphysics]

Why limit pack? Seems like the most valuable element for technology trickle down into production vehicles as well as racing advantages.

 

[flathill]

True. I just do not want to see teams with exclusive access to cells win. If you could guarantee every team have access to the cells then it would be awesome. Then the team with the best battery/system design not cell design will win.

One way to do this would be only to allow cells to be used that are already sold on the open market.

Otherwise its going to be like all the teams have access to 87 Octane while one team sponsored by Company X has Nitro fuel.

F1 controls the fuel spec even though they dont have a sole supplier. If you lab test the fuel it is pretty much identical.

 

[liveforphysics]

I realize who ever has the best battery has the biggest advantage in the races.

That would mean a ton of EV battery development happening. That's a very good thing for the world.

 

[major]

That would mean a ton of EV battery development happening. That's a very good thing for the world.

A better world may not be a priority for those making the regulations

 

[Jonathan in Hiram]

Perhaps a "claiming rule" could work to bring technology costs under control?

https://answers.yahoo.com/question/index?qid=20111117175207AAQS0a1

when you place a claim on someones engine you pay the owner of said engine the amount of what the series or sanctioning body deems the price of a race ready engine would cost to build within its rules, so in other words you don't just claim someones engine and get a free engine, this discourages cheaters from blue printing and throwing more money into an engine than it can be claimed for, so if the claim price is $3000 you don't want to have a $10.000 dollar engine claimed for $3000. Get it? Had an engine claimed once, as the old saying goes, they run best right before they blow, lets just say I didn't get claimed again

 

[doctorGONZO]

I get the torque/ power /rpm thing, but I are you saying you could get this 10x torque with no major implications to the drive controls/inverter etc ?

If done through magnetic geometry alone, it should indeed be possible to suffer no power draw or controller penalty VS any other system with the same final drive torque and power delivered through gearing.

If you want to get fussy about it, you should be capable of a tiny bit smaller controller and battery for the same range and performance desired because some small amount less waste is going into rubbing gear faces together.

.....some small amount less waste is going into rubbing gear faces together.

The standard engineering Rule Of Thumb for the small amount waste is 10% loss of the inputted power for each case of one gear meshing with another in the drive train.

That's why in car talk, manual transmissions are figured to lose 10% and slushomatics lose 30% of the flywheel power.


Welcome
GONZO

 

[doctorGONZO]

If I'm not mistaken, the power electronics required to render mechanical transmissions irrelevant also incur cost, weight, volume, and inefficiency-- just like mechanical transmissions. I don't doubt that either solution could be optimal depending on application and available resources, just as an e-bike direct drive hubmotor is sometimes best and a crank drive is sometimes best, depending on the specific situation.

You are right-on, Chalo.

In perfect conditions in spotless laboratories, optimally designed electric motors have been proved to give amazingly close to 99% efficiency AT CONSTANT LOAD AND RPM. Bearing friction and windage are cruel realities, along with non-superconductor wires. O, and them eddy currents.

But, in real life conditions where the motor has to suffer varying load and RPM, it is almost majicke to get much more than 30%. Geometry that is perfect for one specific combination of load and speed is abominable for other conditions.

How do you get the motor to always give the 99% ? Uhhhh, maybe use a tran. to keep it at the best speed constantly? Might work. Here is a plan: use the tran. to keep the motor running at its best efficiency RPM regardless of vehicle road speed and load!


Welcome
GONZO

 

[doctorGONZO]

When comparing a 1 speed vs a 2 speed EV design you have to pick some metric to match. Here you can see what happens when you pick the gear ratios such that the 0-100km/h time is the same. You can see with a UDDS driver cycle the cars goes about 12 miles farther in this case with the single speed tranny. This paper is pretty comprehensive as it takes into account shift time and adhesion limits, but I'm sure you will find some faults to pick at


Parameter Units Transmission
One-speed/ Two-speed
Optimised ratios — 6.82/ (11.47, 4.64)
Range HWFET km 157.6/ 141.8
Mean motor efficiency HWFET % 86/ 87.2
Range UDDS km 142.1/ 130.4
Mean motor efficiency UDDS % 79/ 80.2
Acceleration 0–100 km/h s 13.48/ 13.49
Acceleration 0–60 km/h s 6.48/ 5.22
Acceleration 50–80 km/h s 4.18/ 4.61
Grade climbing % 25/ 45
Top speed Km/h 151/ 222

That example made up by a transmission company. What do you expect? I've never claimed you can't pick the wrong motor for the job and use a transmission as a crutch to help you get a poor motor choice to function.

Alternatively, you can pick the right motor for the application and be entirely liberated of the dragging around a ginding box of loss.

Luke, you are right when you are talking about a very limited range of application.

For example, for the flying mile, or, the flying five mile, at Bonneville, YOU CAN"T GIVE AWAY THE 10%.

In a car or bike for commuting, wanting to get the best fuel efficiency (yes, Virginia, let's call our electricity a FUEL), you can't be serious saying that NO TRAN. is the best plan.


Best
GONZ

 

[doctorGONZO]

They only use the reduction now because they haven't matured motor geometry sufficiently yet. There is nothing gears can do that a magnetic geometry can't be setup to do, and then you skip the frictional loss and cost and failure modes of the gearing stage.

As usual, Luke, you" explain" using only generalities and abstractions, never any specific quantities.

I believe that you have insufficiently studied the subject and have reached a grossly inaccurate conclusion. I am willing to learn and ask you to direct me to a definitive source of information that explains and proves your position.

What is this majicke geometry that overcomes the historical electric motor efficiency of 30% in varied load and speed conditions? Can you explain it IN SPECIFIC TERMS?


GONZO

 

[Arlo1]

They only use the reduction now because they haven't matured motor geometry sufficiently yet. There is nothing gears can do that a magnetic geometry can't be setup to do, and then you skip the frictional loss and cost and failure modes of the gearing stage.

As usual, Luke, you" explain" using only generalities and abstractions, never any specific quantities.

I believe that you have insufficiently studied the subject and have reached a grossly inaccurate conclusion. I am willing to learn and ask you to direct me to a definitive source of information that explains and proves your position.

What is this majicke geometry that overcomes the historical electric motor efficiency of 30% in varied load and speed conditions? Can you explain it IN SPECIFIC TERMS?


GONZO

Pfft you haven't been around long have you? Ok so eventually you will learn more about Luke and who he is, but putting that aside.
Tell me a case that 2 gear meshing does not use some energy JUST NAME 1. What We are getting at is every set of gears has a loss of energy and this can't be argued. The gears, oil, case and all the parts involved will have a weight and some of them (shift forks etc.) will add drag or losses to the system.
So when you take that same weight worth of parts for a transmission and you add it to motor and controller weight you get a more powerfull motor and you reduce parasitic losses eating up the HP that goes to the wheels and reduce the range. This allows 1 speed with just 1 stage of reduction and with the more powerfull motor you can gear for the same top speed as the top gear in a muti gear setup and end up with the same acceleration and less losses.

There is a 100 page thread discussing this already. You simply don't gain anything by adding more stages of reduction. Multi speed transmissions are needed for gasoline motors because at 0rpm they produce 0 torque but an electric produces full torque.

No matter what gear box you add to an electric motor it will always reduce range on an EV when compared to direct drive done properly.

 

[Punx0r]

The standard engineering Rule Of Thumb for the small amount waste is 10% loss of the inputted power for each case of one gear meshing with another in the drive train.

That's why in car talk, manual transmissions are figured to lose 10% and slushomatics lose 30% of the flywheel power.

Not even close, I'm afraid. A single stage of either spur or helical gears is typically 98-99% efficient

(http://www.roymech.co.uk/Useful_Tables/Drive/Gear_Efficiency.html)

You'd also have to go a long way to find a car with a 30% transmission loss. "no more than 15% of the flywheel power for FWD vehicles and no more than 17% for RWD"

(http://www.pugheaven.co.uk/Transmission%20Losses.htm)

The added inefficiency of an autobox is generally due to the reduced number of ratios and the torque converter, but even then most feature an automatic lock-up to improve efficiency at cruising speed.

 

[liveforphysics]

The standard engineering Rule Of Thumb for the small amount waste is 10% loss of the inputted power for each case of one gear meshing with another in the drive train.

That's why in car talk, manual transmissions are figured to lose 10% and slushomatics lose 30% of the flywheel power.

Not even close, I'm afraid. A single stage of either spur or helical gears is typically 98-99% efficient

(http://www.roymech.co.uk/Useful_Tables/Drive/Gear_Efficiency.html)

You'd also have to go a long way to find a car with a 30% transmission loss. "no more than 15% of the flywheel power for FWD vehicles and no more than 17% for RWD"

(http://www.pugheaven.co.uk/Transmission%20Losses.htm)

The added inefficiency of an autobox is generally due to the reduced number of ratios and the torque converter, but even then most feature an automatic lock-up to improve efficiency at cruising speed.

Chains and oil bathed gears both only show high efficiency at high loads. At low loads (like cruising where fuel economy matters most) they are pretty abysmal if they are also strong enough to handle higher power loads.

Also, I've personally seen >30% loss between the engine dyno to chassis dyno in cases with auto-tragic transmissions (like power glides etc). That 30% comes in the form of X% torque converter slip, X% gear friction, X% transmission pumps and oil drag/windage, X% differential final drive helical (these can be >10% alone), and differential windage/oil drag.

Every series power transfer has loss. Electricity has nothing limiting it from simply being converted into the desired torque/rpm to suit the drive needs, all alternatives involve adding stages of loss, failure modes, cost, noise, complexity and cost.

 

[JackB]

Are the OEM EVs that all use transmissions/gears, those guys are just not very clever?
POWER is TORQUE * RPM. Simple case If you can increase RPM, you have more power.

So we just need a couple 4000 amp 12v hub motors and we are good?

Electric motors efficiency varies over their RPM range,
nothing like an ICE, but it is NOT a flat line.
An issue with cars that go both 5 mph and 75 mph, that is a huge range.

 

[Hillhater]

POWER is TORQUE * RPM. Simple case If you can increase RPM, you have more power.
.

Only if you can keep the same torque at the higher rpm !
....which you cannot with gearing. :wink:

 

[Ohbse]

Are the OEM EVs that all use transmissions/gears, those guys are just not very clever?

Correct. Look at those that are definitely clever to see the way forward. Tesla, Zero, Lightning - even Koenigsegg with the Regera! Direct driven, no transmission and all market leaders in their segments.

Strangely enough all the companies that are in a position to do a 'clean sheet' design have arrived at this, those with the baggage of past experience where transmissions were crucial to success are not willing to adopt radical change and will eventually suffer for it.

As Luke has pointed out many times before a lot of the reasoning behind transmissions in EV's is due to motor limitations present only because of iterative change from the industrial roots of the industry. There are no limitations inherent with the technology, only the narrow implementation of it in mainstream EV components. This will inevitably change.

 

[doctorGONZO]

They only use the reduction now because they haven't matured motor geometry sufficiently yet. There is nothing gears can do that a magnetic geometry can't be setup to do, and then you skip the frictional loss and cost and failure modes of the gearing stage.

As usual, Luke, you" explain" using only generalities and abstractions, never any specific quantities.

I believe that you have insufficiently studied the subject and have reached a grossly inaccurate conclusion. I am willing to learn and ask you to direct me to a definitive source of information that explains and proves your position.

What is this majicke geometry that overcomes the historical electric motor efficiency of 30% in varied load and speed conditions? Can you explain it IN SPECIFIC TERMS?


GONZO

Pfft you haven't been around long have you? Ok so eventually you will learn more about Luke and who he is, but putting that aside.
Tell me a case that 2 gear meshing does not use some energy JUST NAME 1. What We are getting at is every set of gears has a loss of energy and this can't be argued. The gears, oil, case and all the parts involved will have a weight and some of them (shift forks etc.) will add drag or losses to the system.
So when you take that same weight worth of parts for a transmission and you add it to motor and controller weight you get a more powerfull motor and you reduce parasitic losses eating up the HP that goes to the wheels and reduce the range. This allows 1 speed with just 1 stage of reduction and with the more powerfull motor you can gear for the same top speed as the top gear in a muti gear setup and end up with the same acceleration and less losses.

There is a 100 page thread discussing this already. You simply don't gain anything by adding more stages of reduction. Multi speed transmissions are needed for gasoline motors because at 0rpm they produce 0 torque but an electric produces full torque.

No matter what gear box you add to an electric motor it will always reduce range on an EV when compared to direct drive done properly.

Pfft you haven't been around long have you? Ok so eventually you will learn more about Luke and who he is, but putting that aside.

Well, Luke groupie, tell me just Who luke is, and then we can put it aside. Is luke your boyfriend, is that Who He is? He is real pretty. When I was a young and beautiful man, I was only a little bit prettier. At least, that is what all the girls told me. I don't know what all the boys thought. I have never cared about what the boys thought.

I haven't been around a long time? LAUGHING MY ASS OFF ROLLING ON THE FLOOR. Tell me your age, you silly young bastard.

Tell me a case that 2 gear meshing does not use some energy JUST NAME 1.

You seem to be awfully damn confused. MY POINT WAS that a transmission DOES waste energy. Are you one of those dyslexic fools that read everything backward?


The remainder of your silly bla bla is just plain laughable. Not BUST MY GUT laughable. You do not understand that any electric motor that has ever been made has one "sweet spot" speed where it has its best efficiency and where it has it has its best performance. And obviously your adored Luke has never learned it either.



Sweet Dreams
GONZ

 

[doctorGONZO]

The standard engineering Rule Of Thumb for the small amount waste is 10% loss of the inputted power for each case of one gear meshing with another in the drive train.

That's why in car talk, manual transmissions are figured to lose 10% and slushomatics lose 30% of the flywheel power.

Not even close, I'm afraid. A single stage of either spur or helical gears is typically 98-99% efficient

(http://www.roymech.co.uk/Useful_Tables/Drive/Gear_Efficiency.html)

You'd also have to go a long way to find a car with a 30% transmission loss. "no more than 15% of the flywheel power for FWD vehicles and no more than 17% for RWD"

(http://www.pugheaven.co.uk/Transmission%20Losses.htm)

The added inefficiency of an autobox is generally due to the reduced number of ratios and the torque converter, but even then most feature an automatic lock-up to improve efficiency at cruising speed.

Not even close, I'm afraid. A single stage of either spur or helical gears is typically 98-99% efficient

YOU are not even close. But, I AM afraid of trusting anything you say from now on. Your link was for RIGHT ANGLE DRIVES and UNDER 50 HP. I was talking about straight-line drive trains like in a car.

However, assuming that if you were correct, you have not proved anything in your favor. My intention was to point out that any electric motor needs to be kept at its "sweet Spot" RPM. And when that does not take place, historically, for over 100 years, electric motors have consistently been tested and reported to give little better than 30% efficiency when operated in real-world car-like conditions of varying load and speed, like driving in downtown rush-hour traffic.

So, if you were somehow right, a tran. would waste 1.5% power (on average) to save perhaps as much as 70% power by keeping the motor on the "Sweet Spot".

Did you understand any of the preceding? Ooops. "preceding" means; what I just said. Sorry for using a big word.


GONZO

 

[doctorGONZO]

The standard engineering Rule Of Thumb for the small amount waste is 10% loss of the inputted power for each case of one gear meshing with another in the drive train.

That's why in car talk, manual transmissions are figured to lose 10% and slushomatics lose 30% of the flywheel power.

Not even close, I'm afraid. A single stage of either spur or helical gears is typically 98-99% efficient

(http://www.roymech.co.uk/Useful_Tables/Drive/Gear_Efficiency.html)

You'd also have to go a long way to find a car with a 30% transmission loss. "no more than 15% of the flywheel power for FWD vehicles and no more than 17% for RWD"

(http://www.pugheaven.co.uk/Transmission%20Losses.htm)

The added inefficiency of an autobox is generally due to the reduced number of ratios and the torque converter, but even then most feature an automatic lock-up to improve efficiency at cruising speed.

Chains and oil bathed gears both only show high efficiency at high loads. At low loads (like cruising where fuel economy matters most) they are pretty abysmal if they are also strong enough to handle higher power loads.

Also, I've personally seen >30% loss between the engine dyno to chassis dyno in cases with auto-tragic transmissions (like power glides etc). That 30% comes in the form of X% torque converter slip, X% gear friction, X% transmission pumps and oil drag/windage, X% differential final drive helical (these can be >10% alone), and differential windage/oil drag.

Every series power transfer has loss. Electricity has nothing limiting it from simply being converted into the desired torque/rpm to suit the drive needs, all alternatives involve adding stages of loss, failure modes, cost, noise, complexity and cost.

O, so NOW Tarzan has decided to give a little bit of definition to his high-flying hyperbolic poetry. Run out of weed? Your head got momentarily clear?

Tarzan, pretty man Tarzan, in the REAL WORLD of electric motors, operated in REAL WORLD conditions of driving an e-car in REAL WORLD downtown rush hour stop n go gridlock traffic, all electric motors operate OFF their "Sweet Spot" MOST of the time, bike or car, tell me, tell me, in your own words or less, how your MAJICKE GEOMETREYE motor avoids eddy current loss, current resistance loss in stall, or, semi-stall, excess current draw when not in the perfect counter emf state, yadda yada, and operates at about 99% efficiency without a 'box to keep it at the perfect RPM??


Adoringly yours
GONZO

 

[doctorGONZO]

Lukey, pretty baby, it is not obvious that you know what I'm talking about when I write about the 70% loss in the normal electric motor operated in varying load and RPM conditions.

So, why don't you explain to us how and why the normal motor has been losing 70% of its input power for over 100 years?

Then we can believe that you are not only beautiful but also brainy.


GONZO

 

[h0tr0d]

Gonzo,

Please comment this:

 

[Punx0r]

Chains and oil bathed gears both only show high efficiency at high loads. At low loads (like cruising where fuel economy matters most) they are pretty abysmal if they are also strong enough to handle higher power loads.

Also, I've personally seen >30% loss between the engine dyno to chassis dyno in cases with auto-tragic transmissions (like power glides etc). That 30% comes in the form of X% torque converter slip, X% gear friction, X% transmission pumps and oil drag/windage, X% differential final drive helical (these can be >10% alone), and differential windage/oil drag.

True. Part load efficiency is less and the 98-99% was for friction only at full load, without windage losses if they are immersed in oil. However, part load efficiency appears to be an exponential curve, so the "low efficiency" area at low load is pretty small.

Also, I'd take a 2-speed Powerglide as "going a long way" to find a 30% transmission loss I've read of those things but don't think I've ever seen one

I'm not arguing that transmissions are good or appropriate for EVs. I just don't buy the rule-of-thumb of "10% per stage" for gear transmissions as applying to all automotive transmissions. That "rule" ignores gear type, speed, load and ratio. Over-inflated transmission losses from chassis dynos is also a pet-hate of mine. It's not unusual to see someone proudly showing off a dyno curve with a 35 or 40% stated power correction for transmission loss... A typical manual transmission has two gear stages (let's assume the diff is locked). So we'd be looking at 1 x 0.9 x 0.9 = 81% efficient. Then add losses for the CV joints and tyres (I understand the latter are considerable [dyno losses on cars with soft tyres]). It just seems too much.

I couldn't find much on modern autobox efficiency but Mercedes quote 93% for the torque converter for their new 9-speed Vs. 85% for their older 7-speed. That's pretty bad, but I've never been a fan of autoboxes due to their relatively poor efficiency and performance. Easier in heavy traffic, though. Anyways, at least it'd be locked up from about ~50mph.

 

[Punx0r]

There's a neat little quote from Christian von Koenigsegg talking about the new Koenigsegg Regera, which uses a twin-turbo V10 petrol engine with a crank-drive electric motor, connected to two rear wheel hub motors. No transmission, all direct drive (with a hydraulic coupling to engage/disengage the engine at low speed). 700HP from the electric motors + 1100HP from the ICE.


"We managed to take a heavy, expensive lump out of the equation [the transmission], without sacrificing the ability of the combustion engine to provide drive to the rear wheels...Why remove the transmission completely? "I've been wanting to create something like this without a CVT's horrible elasticity, and the weight and complexity transmissions bring," Christian tells TG. "I came up with the idea last summer, and calculated that there is no need to have any gears. It was a eureka moment for me!""

(http://www.topgear.com/uk/car-news/koenigsegg-regera-revealed-geneva-motor-show-2015-03-03)

 

[Arlo1]

There's a neat little quote from Christian von Koenigsegg talking about the new Koenigsegg Regera, which uses a twin-turbo V10 petrol engine

Its a V8 based on the ford 5.0

 

[Arlo1]

Lukey, pretty baby, it is not obvious that you know what I'm talking about when I write about the 70% loss in the normal electric motor operated in varying load and RPM conditions.

So, why don't you explain to us how and why the normal motor has been losing 70% of its input power for over 100 years?

Then we can believe that you are not only beautiful but also brainy.


GONZO

We don't ban many from this forum but keep at it and you might get there.

ALL motors are 0% efficient at 0 rpm. Just because you use a transmission doesn't mean the motor is not going to have to start at 0rpm Do you think you would use a clutch or torque converter?

Have you any experience in the EV world at all or is all your "knowledge" from graphs and data posted online?