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[Richard230]

Kymco displays an interesting electric motorcycle concept with excellent performance claims. But why a 6-speed transmission and did they build it just for fun or will it actually be sold to consumers some day?
https://electricmotorcycles.news/kymcos-revonex-unveiled-at-eicma-by-chairman-allen-ko-video/

[ultratoad]

Kymco displays an interesting electric motorcycle concept with excellent performance claims. But why a 6-speed transmission and did they build it just for fun or will it actually be sold to consumers some day?
https://electricmotorcycles.news/kymcos-revonex-unveiled-at-eicma-by-chairman-allen-ko-video/

Gear boxes and electric motors actually go hand in hand, especially when it comes to racing applications.  RPM does have an affect on torque and horsepower production in electric motors, although not at the levels seen in ICE units.  AND that is why Formula E cars have a 5 speed gear box.  Making the power to energy levels as efficient as possible. 

[Richard230]

Kymco displays an interesting electric motorcycle concept with excellent performance claims. But why a 6-speed transmission and did they build it just for fun or will it actually be sold to consumers some day?
https://electricmotorcycles.news/kymcos-revonex-unveiled-at-eicma-by-chairman-allen-ko-video/

Gear boxes and electric motors actually go hand in hand, especially when it comes to racing applications.  RPM does have an affect on torque and horsepower production in electric motors, although not at the levels seen in ICE units.  AND that is why Formula E cars have a 5 speed gear box.  Making the power to energy levels as efficient as possible.

But is the weight, complexity and additional cost of a six-speed transmission worth it for the commercial market?

[ultratoad]

Kymco displays an interesting electric motorcycle concept with excellent performance claims. But why a 6-speed transmission and did they build it just for fun or will it actually be sold to consumers some day?
https://electricmotorcycles.news/kymcos-revonex-unveiled-at-eicma-by-chairman-allen-ko-video/

Gear boxes and electric motors actually go hand in hand, especially when it comes to racing applications.  RPM does have an affect on torque and horsepower production in electric motors, although not at the levels seen in ICE units.  AND that is why Formula E cars have a 5 speed gear box.  Making the power to energy levels as efficient as possible.

But is the weight, complexity and additional cost of a six-speed transmission worth it for the commercial market?

Ahhh....  The age old question....  Porsche or Volkswagon ?

[JaimeC]

Gear boxes and electric motors actually go hand in hand, especially when it comes to racing applications.  RPM does have an affect on torque and horsepower production in electric motors, although not at the levels seen in ICE units.  AND that is why Formula E cars have a 5 speed gear box.  Making the power to energy levels as efficient as possible.

I would point out that the bikes used in MotoE are a single, fixed gear...

[BrianTRice@gmail.com]

I've heard a claim that the Formula E teams/cars with gearboxes are not clear winners. I can't figure out how to back that up or refute that, despite engineering reasons in favor of gearboxes in addition to tradeoffs.

I tend to think "people like different things" as enough reason to go one way or another. A gearbox is extremely low on the list of technologies I'd want my preferred OEM to apply to their vehicles. Air resistance is so much more significant to powertrain losses than the torque curve.

[Moto7575]

Agree. I cant see how this can be a priority compared to lower cost, wright or increased battery.

I've heard a claim that the Formula E teams/cars with gearboxes are not clear winners. I can't figure out how to back that up or refute that, despite engineering reasons in favor of gearboxes in addition to tradeoffs.

I tend to think "people like different things" as enough reason to go one way or another. A gearbox is extremely low on the list of technologies I'd want my preferred OEM to apply to their vehicles. Air resistance is so much more significant to powertrain losses than the torque curve.

[siai47]

Electric motors have a "sweet spot" based on RPM and input voltage where the motor runs at it's highest efficiency.  Therefore, it is a benefit to have some sort of gearbox to keep the motor in that operating range---to a point.  For example my Victory (Brammo) Empulse TT has a 6 speed gearbox.  The object (according to the riders manual) is to operate the bike in the green arc on the tachometer which is between 4500 and 6500 RPM.  This is because the bikes motor runs at it's highest efficiency at 5500 RPM.  Either side of that, there is a slight efficiency loss.

That being said, I cannot make a case for a 6 speed gearbox.  Maybe a 2 speed but no more for a street bike.  I tend to ride the bike in 2nd gear around town and 4th gear on the highway.  With only 54 HP the bike will run alright through its usable speed range by just leaving it in 4th or 3rd but is a little short on acceleration from a stop.  Riding and shifting to keep the motor as close to 5500 RPM as you can isn't worth the almost negligible increase in range you might see.  When I ride the SR/F with double the horsepower of the Empulse and only 39 pounds more weight, I don't feel there is any need for a gearbox's noise, clutch, weight and complexity.  If you are tracking the bike, a 2 speed planetary transmission might be a help.  But for the street I want an electric bike to be quiet.  The direct belt drive is the answer.  I'll take a little belt noise over gear and chain noise any day.       

[shayan]

Electric motors have a "sweet spot" based on RPM and input voltage where the motor runs at it's highest efficiency.  Therefore, it is a benefit to have some sort of gearbox to keep the motor in that operating range---to a point.  For example my Victory (Brammo) Empulse TT has a 6 speed gearbox.  The object (according to the riders manual) is to operate the bike in the green arc on the tachometer which is between 4500 and 6500 RPM.  This is because the bikes motor runs at it's highest efficiency at 5500 RPM.  Either side of that, there is a slight efficiency loss.

That being said, I cannot make a case for a 6 speed gearbox.  Maybe a 2 speed but no more for a street bike.  I tend to ride the bike in 2nd gear around town and 4th gear on the highway.  With only 54 HP the bike will run alright through its usable speed range by just leaving it in 4th or 3rd but is a little short on acceleration from a stop.  Riding and shifting to keep the motor as close to 5500 RPM as you can isn't worth the almost negligible increase in range you might see.  When I ride the SR/F with double the horsepower of the Empulse and only 39 pounds more weight, I don't feel there is any need for a gearbox's noise, clutch, weight and complexity.  If you are tracking the bike, a 2 speed planetary transmission might be a help.  But for the street I want an electric bike to be quiet.  The direct belt drive is the answer.  I'll take a little belt noise over gear and chain noise any day.       

Having been an Empulse TT owner before, i cannot agree more.
1. 6 speed gearbox was way too much. 3-4 gears at the most would've been better. But i guess iet did not manufacture with that spec
2. There have been a lot of Empulse owners with leaking transmission oil issues (including mine).
    So i guess its not as easy to integrate the motor and gearbox into one unit

However, the acceleration in first gear was truly good! I would say as much as or better than the Zero S 2018+ (Which has the updated motor and controller)
Gearbox also obviously helped in regen braking. On a steep enough downhill in 1st gear, i would see about 4.5kW worth of DC power going into the battery.
If the issues with complexity and weight can be addressed, i guess it would be a good addition. It would also allow for a smaller motor to be used. So it should be designed to have a comparable total weight with a single speed - big motor combo.

-Shayan

[Richard230]

It is my opinion that EV companies that use a 6-speed gearbox in their bikes are doing so because that is what is available "off-the-shelf".  It is very expensive to design and manufacture (and purchase) a motorcycle gearbox from scratch. But if you can find one that has the ability to handle the torque of an electric motor and is currently being used in another ICE vehicle, just having the manufacturer supply it to you is likely to be better than any other option for a small company. All you might have to do is to design and manufacture the gearbox case - if you really have an urge to use a gearbox, such as Brammo did for the Emluse.

BMW tends to bounce back and forth between Getrag and another gearbox company, but with their resources, reputation and finances, they can afford to do that. And having a huge auto market likely helps back up their selection and ability to purchase dedicated gearboxes for their motorcycles.

I think Zero has said more than once that the reason that they didn't place a gearbox in their bikes is mostly because of development costs, followed by the space required for the components in a small motorcycle chassis.

[togo]

Electric motors do have an efficiency band and the larger the motor the larger the efficiency band.

Electric vehicle manufacturers soon learn that having larger motors does not harm them from the efficiency perspective like it does with internal combustion vehicles. So simply oversizing the motor and controller gives you what a mulitspeed gearbox would have given you without the additional complexity and you are rewarded with higher acceleration (which customers love) and more regenerative braking. See: Tesla

Not that a single speed gearbox is unusual. Tesla uses a 9 to 1, I believe, and Energica does something similar.

[T.S. Zarathustra]

But is the weight, complexity and additional cost of a six-speed transmission worth it for the commercial market?

You need to look at the total package. Having gearbox allows you to use smaller motor, while keeping same acceleration and top speed. Having smaller motor allows you to use cheaper electronics, and smaller batteries. So having a multispeed gearbox (they all have a gearbox, it's just that most gearboxes are single speed) can reduce the total weight, and cost, of a bike.

[togo]

I will buy the argument of cost savings, especially for companies that are already accustomed to small power band.

I wont buy the simplicity argument.  It's just not so. If you have a controller, it's not more complex to have one powerful enough to do the job. If you have an electric motor, it's not more complex to have one powerful enough to do the job. A transmission is always more complex than no transmission. Unless you have a gasoline assembly line and you are wanting to fit electric into that mentality. And we have plenty examples of that being a losing strategy. Fossil fuel vehicle companies need to commit to the transition, not try to fit electric into their existing small power band designs.

[Crissa]

It's certainly more expensive to build a controller capable of handling more current.

-Crissa

[togo]

It's certainly more expensive to build a controller capable of handling more current.

-Crissa

There are plenty available off the shelf, but if you need a custom one, yes.