Martin A
10 W
I think the main problem here is a question of semantics or definition of what a gearbox is, which is why this topic seems to be going on and on.
To my mind a gearbox is a device that will enable more than one gear ratio to be selected between the motor and the wheel rim while the vehicle is in motion. i.e the distance travelled per motor revolution is variable. The Tesla does not have this facility, Luke's deathbike (and other single stage reduction bikes) don't and neither do those bikes with gearless hubmotors, but all vehicles must have some sort of gearing even if that is just the distance between the motor shaft and the tyre/road interface.
With an electric road vehicle there are other factors that come into play, namely packaging and unsprung weight, that may result in a necessary compromise of removing the motors from being directly in the wheel, due to the undesireable effects they have on ride and handling.
It is the excess weight of variable gear ratios, devices to enable changing of ratio and all the attendant packaging, in a badly designed electric vehicle drive system that means they are not the best solution (unlike in a diesel or petrol vehicle). The excess weight would be better used in an electric motor designed for the machine and producing more power.
What does make them seemingly awesome is when the excess weight and bad system design is ignored.
Having said that, there may be a case for a fixed length chain from chainwheel to hub that would allow the drive and driven gear to be interchanged when stationary. As this would involve no extra weight, it may be that such a solution may provide a compromise for vehicles with distinct different service duties and a large overall speed range, but you'd have to ask the maths and physics guys about that.
To my mind a gearbox is a device that will enable more than one gear ratio to be selected between the motor and the wheel rim while the vehicle is in motion. i.e the distance travelled per motor revolution is variable. The Tesla does not have this facility, Luke's deathbike (and other single stage reduction bikes) don't and neither do those bikes with gearless hubmotors, but all vehicles must have some sort of gearing even if that is just the distance between the motor shaft and the tyre/road interface.
With an electric road vehicle there are other factors that come into play, namely packaging and unsprung weight, that may result in a necessary compromise of removing the motors from being directly in the wheel, due to the undesireable effects they have on ride and handling.
It is the excess weight of variable gear ratios, devices to enable changing of ratio and all the attendant packaging, in a badly designed electric vehicle drive system that means they are not the best solution (unlike in a diesel or petrol vehicle). The excess weight would be better used in an electric motor designed for the machine and producing more power.
What does make them seemingly awesome is when the excess weight and bad system design is ignored.
Having said that, there may be a case for a fixed length chain from chainwheel to hub that would allow the drive and driven gear to be interchanged when stationary. As this would involve no extra weight, it may be that such a solution may provide a compromise for vehicles with distinct different service duties and a large overall speed range, but you'd have to ask the maths and physics guys about that.