4 ms·

Do EV's have gearboxes?

by Narkov 7y ago

Gibbon1 7y ago
I think usually a single reduction gear, sometimes a differential.
thesz 7y ago
Yes, they do and easy to screw up. Learn about first model of Tesla Roadster - it was quite speedy up to 160 km/h and then not speedy at all. All because of the wrong gearbox. https://en.wikipedia.org/wiki/Tesla_Roadster_(2008)#Transmission https://en.wikipedia.org/wiki/Tesla_Roadster_(2008)#Transmis...
jansan 7y ago
Porsche Taycan has a two-speed gearbox, probably developed by or with Rimac.
JoachimS 7y ago
Some do, some don't. The Koenigsegg hybrid (so not strictly an EV, but can be operated as a pure EV) famously don't have a gearbox but a single, fixed reduction gear. There is a hydraulic coupling for the electrical motors to allow slow speeds. At higher speeds the coupling is mechanically locked to directly connect all engines to the wheels. https://en.wikipedia.org/wiki/Koenigsegg_Regera https://en.wikipedia.org/wiki/Koenigsegg_Regera https://www.koenigsegg.com/car/regera/ https://www.koenigsegg.com/car/regera/
- deleted 7y ago
  [deleted]
- balfirevic 7y ago
  There seems to be some language confusion here. Single speed gearbox is still called a gearbox.
AgloeDreams 7y ago
Model S/X/3/Y all have a reduction gear but no multi-speed transmission, same for all others other than the Taycan.
danans 7y ago
The Mitsubishi Outlander phev, which only directly powers the wheels with the ICE in specific modes, uses only a hydraulic clutch for that purpose. There might be a fixed gear reduction somewhere, but no true gearbox.
anordal 7y ago
If you exclude hybrids, 99.999% of EVs don't have gearboxes (unless you count single-speed ones), despite media labelling them as "automatic". As mentioned, Taycan and the preprod Roadster are exceptions, and those are also the two exceptions I know.
frankus 7y ago
If by "EV" you mean "electric car", then they almost always do (and it's almost always a single fixed reduction, around 10:1). But a lot of non-car electric vehicles (maybe the majority) use hub motors, where the wheel's angular velocity is the same as the motor's. That's not the whole story, though, as a more illustrative number is the ratio between wheel radius and the motor's air gap radius, multiplied by whatever reduction gearing is used. I don't think there's a name for this concept, but you could borrow "gain ratio" from bicycles (https://sheldonbrown.com/gain.html https://sheldonbrown.com/gain.html). For a hub motor the wheel pretty much has to be bigger than the motor for ground clearance (unless you're a monorail or something), so the gain ratio is less than one (maybe 0.5 for a skateboard and 0.25 for an ebike). And practical wheel speeds tend to be a lot lower than even an inexpensive motor's top speed (not surprisingly, by about a 10:1 ratio). Bottom line is a hub motor tends to be ~10 times larger than it would need to be on a peak torque basis, so fitting more torque into a smaller package (even at the expense of top speed) is a win. On the other hand solving the peak torque issue doesn't magically solve other issues that might crop up as you downsize (e.g. heat).

Do EV's have gearboxes?

by Narkov 7y ago

Do EV's have gearboxes?

Gibbon1 7y ago

I think usually a single reduction gear, sometimes a differential.

thesz 7y ago

Yes, they do and easy to screw up. Learn about first model of Tesla Roadster - it was quite speedy up to 160 km/h and then not speedy at all. All because of the wrong gearbox. https://en.wikipedia.org/wiki/Tesla_Roadster_(2008)#Transmission https://en.wikipedia.org/wiki/Tesla_Roadster_(2008)#Transmis...

jansan 7y ago

Porsche Taycan has a two-speed gearbox, probably developed by or with Rimac.

JoachimS 7y ago

Some do, some don't. The Koenigsegg hybrid (so not strictly an EV, but can be operated as a pure EV) famously don't have a gearbox but a single, fixed reduction gear. There is a hydraulic coupling for the electrical motors to allow slow speeds. At higher speeds the coupling is mechanically locked to directly connect all engines to the wheels. https://en.wikipedia.org/wiki/Koenigsegg_Regera https://en.wikipedia.org/wiki/Koenigsegg_Regera https://www.koenigsegg.com/car/regera/ https://www.koenigsegg.com/car/regera/

deleted 7y ago
[deleted]
balfirevic 7y ago
There seems to be some language confusion here. Single speed gearbox is still called a gearbox.

AgloeDreams 7y ago

Model S/X/3/Y all have a reduction gear but no multi-speed transmission, same for all others other than the Taycan.

danans 7y ago

The Mitsubishi Outlander phev, which only directly powers the wheels with the ICE in specific modes, uses only a hydraulic clutch for that purpose. There might be a fixed gear reduction somewhere, but no true gearbox.

anordal 7y ago

If you exclude hybrids, 99.999% of EVs don't have gearboxes (unless you count single-speed ones), despite media labelling them as "automatic". As mentioned, Taycan and the preprod Roadster are exceptions, and those are also the two exceptions I know.

frankus 7y ago

If by "EV" you mean "electric car", then they almost always do (and it's almost always a single fixed reduction, around 10:1). But a lot of non-car electric vehicles (maybe the majority) use hub motors, where the wheel's angular velocity is the same as the motor's. That's not the whole story, though, as a more illustrative number is the ratio between wheel radius and the motor's air gap radius, multiplied by whatever reduction gearing is used. I don't think there's a name for this concept, but you could borrow "gain ratio" from bicycles (https://sheldonbrown.com/gain.html https://sheldonbrown.com/gain.html). For a hub motor the wheel pretty much has to be bigger than the motor for ground clearance (unless you're a monorail or something), so the gain ratio is less than one (maybe 0.5 for a skateboard and 0.25 for an ebike). And practical wheel speeds tend to be a lot lower than even an inexpensive motor's top speed (not surprisingly, by about a 10:1 ratio). Bottom line is a hub motor tends to be ~10 times larger than it would need to be on a peak torque basis, so fitting more torque into a smaller package (even at the expense of top speed) is a win. On the other hand solving the peak torque issue doesn't magically solve other issues that might crop up as you downsize (e.g. heat).