Hello,
How do gears work in an electric car?
How do gears work in an electric car?
Gears in electric car
they do not have gears as such i believe, apart from a single gear set to whatever ratio.
https://www.drivingelectric.co ... ctric-cars-have-gearboxes
As electric cars produce maximal torque across whole rev spectrum, the gearbox for keeping revs in optimal range is not necessary. Therefore they usually only have one fixed gear for any speed (although some experimental/racing crafts can have high/low gear four whatever reason).
also if you want the ratio of a given pair of spur gears is calculated by dividing the number of teeth on the driven gear, by the number of teeth on the drive gear
Electric cars can still benefit from gearing, but far less so than combustion engines. Low speed acceleration is generally already more than competitive. Keeping power at higher speeds is not really a concern for your typical road car, given that manufacturers are now looking to bring top speeds down. As such, the extra cost and complexity is not needed.
No gearbox also makes packaging the a motors into the each wheel much more practical and then you don't need a differential either and can just rely on electronic torque vectoring for managing stability and variant wheel speeds. It's a more modern but ultimately much more flexible solution.
No gearbox also makes packaging the a motors into the each wheel much more practical and then you don't need a differential either and can just rely on electronic torque vectoring for managing stability and variant wheel speeds. It's a more modern but ultimately much more flexible solution.
^^ informative and true. never had a chance to say hi before, so hi bob great to meet you
Two of the main limiting factors as of now for geared electrical motors are the torque output and high rpm. The higher the torque output, the stronger the gears/shafts/bearings need to be which in terms adds roational mass that can not spin at infinite rpm.
The general concept of dc (brushless) electrical engines have current output limit that in term limits the 0 to low rpm torque output. As rpm's rise, torque increases as to a point that voltage becomes the bottleneck. Top end rpm is achieved by dropping the current, as so torque drops dramatically.
Ive been toying with the idea of a CVT gearbox, purely for simplicity sake, engine torque can be limited at all times so it will not cause slip in the belt driven conical gears of a CVT, top end rpm can be given a little boost in torque as CVT can provide a more suiting gearing ratio... its all just theory.
Rimac use a nice and well packed design on two gears (low and tall) gearbox, that seems to be working well for them and their customers.
The general concept of dc (brushless) electrical engines have current output limit that in term limits the 0 to low rpm torque output. As rpm's rise, torque increases as to a point that voltage becomes the bottleneck. Top end rpm is achieved by dropping the current, as so torque drops dramatically.
Ive been toying with the idea of a CVT gearbox, purely for simplicity sake, engine torque can be limited at all times so it will not cause slip in the belt driven conical gears of a CVT, top end rpm can be given a little boost in torque as CVT can provide a more suiting gearing ratio... its all just theory.
Rimac use a nice and well packed design on two gears (low and tall) gearbox, that seems to be working well for them and their customers.
I have been thinking about this subject and one good solution is the planetary gear system. This type of gearing is very flexible and it has many options. You can either choose to make a planetary gear system which increases the output RPM (at the same time, decreses the output torque by the same ration) or decreases.
planetary gears
According to this picture, if the sun-gear is spinning at 3000rpm (the standard top spped for an AC motor), the planet-gears will be spinning at 7000rpm (more or less the max rpm for a standard road car). The output torque will be lessened by the same ratio of imput and output speeds.
planetary gears
According to this picture, if the sun-gear is spinning at 3000rpm (the standard top spped for an AC motor), the planet-gears will be spinning at 7000rpm (more or less the max rpm for a standard road car). The output torque will be lessened by the same ratio of imput and output speeds.
You can benefit from gearing in electrics. Way less than in normal engines though.
That doesn't make sense. One of the three (ring, planet carrier, sun) has to be held in place, otherwise you can't transmit any torque.
Having gears on electric cars would be of no benefit, they just do not need them to run efficiently,and it would only add weight which would then have a negative effect for no improvement in the running of said engines
https://www.greenoptimistic.com/electric-cars-gears/
Hello!
The porsche taycan also has a transmission with two gears as shown here: https://presse.porsche.de/prod ... lle-taycan-taycan_turbo_s
Even if most electric vehicles do not need a transmission, because of the way electric motors deliver their power over the whole rpm range, a car aimed at performance can benefit from varying gear ratios to deliver more torque to the wheels.
peace, mo
The porsche taycan also has a transmission with two gears as shown here: https://presse.porsche.de/prod ... lle-taycan-taycan_turbo_s
Even if most electric vehicles do not need a transmission, because of the way electric motors deliver their power over the whole rpm range, a car aimed at performance can benefit from varying gear ratios to deliver more torque to the wheels.
peace, mo
That's a nice exploded diagram, thanks for sharing
While it has a double ratio any actual performance gain is minimal if not none existent between the taycan turbo s and the tesla model s cheetah stance, i guess it depends on whatever scenario the vehicle is being used for, for racing for city driving. To be honest the only knowledge i have of electric motors is in RC racing from a good few years ago and only my Traxxas sports maxx nitro had an upgraded 2 speed while my HP Racing electric car was single speed.
The original plan for the Tesla vehicles was a two speed gearbox, but this was changed to two different fixed gears running at the same time, possible due to the multiple engine layout.
Some further reading: https://cleantechnica.com/2019/07/22/ev-transmissions-are-coming-and-its-a-good-thing/
Some further reading: https://cleantechnica.com/2019/07/22/ev-transmissions-are-coming-and-its-a-good-thing/
Hello!
Today even the most powerfull performance electric vehicles cap out at a relative low top speed compared to vehicles with combustion engines.
While a top speed around 150-200 km/h might be enough for most parts of the world, here in germany we are used to cars with top speeds way above 200 km/h.
So while it is true that an electric motor can deliver the same torque across its whole rpm range that also means that the rpm of the motor is directly proportional to the driven wheel speed.
If you now implement a transmission you can accieve lower motor rpm at higher wheel speed which is not only a comfort advantage but also allows for higher top speed.
So there are use case scenarios in which an electric vehicle could benefit from a transmission even if most electric vehicles do not need any form of transmission.
peace, mo
Today even the most powerfull performance electric vehicles cap out at a relative low top speed compared to vehicles with combustion engines.
While a top speed around 150-200 km/h might be enough for most parts of the world, here in germany we are used to cars with top speeds way above 200 km/h.
So while it is true that an electric motor can deliver the same torque across its whole rpm range that also means that the rpm of the motor is directly proportional to the driven wheel speed.
If you now implement a transmission you can accieve lower motor rpm at higher wheel speed which is not only a comfort advantage but also allows for higher top speed.
So there are use case scenarios in which an electric vehicle could benefit from a transmission even if most electric vehicles do not need any form of transmission.
peace, mo
In Formula E some team(s) have direct-drive but other teams are using anything from 2 to 5 gears.
Another thing to consider is maybe:
In formular cars one does probally not want to use engines in the wheel hubs.
It would be a large unsprung mass and maybe take away space for brake discs.
Some gearing is needed anyway because the engine would spin way too fast to directly drive the wheels. At that point adding a few shiftable gears is maybe only a relative small step. The added weight should not be that much, there is basically no loss in effiency and gearboxes are a tried and tested technology, there is no risk in using them.
Another thing to consider is maybe:
In formular cars one does probally not want to use engines in the wheel hubs.
It would be a large unsprung mass and maybe take away space for brake discs.
Some gearing is needed anyway because the engine would spin way too fast to directly drive the wheels. At that point adding a few shiftable gears is maybe only a relative small step. The added weight should not be that much, there is basically no loss in effiency and gearboxes are a tried and tested technology, there is no risk in using them.
Why do you assume "some gearing is needed anyway"? A 225/45 R17 wheel @ 60km/h results in 500 rpm for the wheel. Drivetrains were always about slowing engine output down for the driven wheels. ~1000 rpm at 120 km/h seems perfectly reasonable for an electric engine.
the formular e engines have a max-rpm of ~20.000 rpm
All current geneation Formula E cars use single gear.
There is a reduction between the motor and the wheels, but there are no shiftable gears anymore.
There is a reduction between the motor and the wheels, but there are no shiftable gears anymore.
Well which is it now? Or is there a massive flaw in my estimates?
5tag:
by your estimates at 225 km/h (topspeed) the engine would have an an rpm of ~2000. But actually it is ten times higher at 20.000rpm. I do not know why they use such high-rpm engines, but it means a reduction gear is needed.
michal:
ah, that must have changed since when I last watched formular E. (which was a bit ago
)
by your estimates at 225 km/h (topspeed) the engine would have an an rpm of ~2000. But actually it is ten times higher at 20.000rpm. I do not know why they use such high-rpm engines, but it means a reduction gear is needed.
michal:
ah, that must have changed since when I last watched formular E. (which was a bit ago
)Yeah, Formula E evolved massively in a very short time, their current topspeed is now close to 280 km/h as the power output increased to 250 kW
Fastest electric car has a top speed of 210mph and some get 0-60mph in around 1.6s which leaves the majority of cars for dust
EVs have low top soeed just because of energy consumption, not because lack of power.
My EV is locked at 168kmh (by gps) and it achieves that speed with no trouble. Also no teouble in maintaining it over longer period of time. But energy consumption goes through the roof (close to 35 kw per 100km).
My EV is locked at 168kmh (by gps) and it achieves that speed with no trouble. Also no teouble in maintaining it over longer period of time. But energy consumption goes through the roof (close to 35 kw per 100km).
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Gears in electric car
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