A passenger car diesel engine, if it wants to impress, developes about 500 Nm of torque or more. Even in the direct gear it is transfered still about 1500 Nm by the axle drive. In lower gears it can be up to 4000 Nm.

Half of these values would already bring two wheel hub motors, if you wanted to move the vehicle with similarly impressive torque. Since electric motors from standstill produce torque, case of the car you would be satisfied with most 1000 Nm per wheel. After all, one could take four wheel hub motors also still.

Namely, there is unfortunately an important argument against wheel hub motors: they increase the unsprung masses. Thus they change the relationship to the sprung mass, against which they must be supported at uneven roads. If they exceed a certain size, also hard damping does not help much. The weight is an argument against more powerful wheel hub motors.

In the above shown example the physical conditions look a bit different. The bus has a much better ratio of sprung to unsprung mass. It copes with the disadvantages of the hub motor significantly better. It also has a problem of space because of a very low floor and not enough front space for cooling, which the concept shown above elegantly solves.

Regarding the efficiency between energy storage and conversion, of course, the hub motor is unmatched. Come in addition that this high level of efficiency and of course in the recovery of energy (braking recuperation) plays a role. Here you have an example, how the brake can be better integrated saving more weight.

The manufacturer of ZAwheels makes even possible a conversion of conventional buses, so the complete removal of all necessary elements for the drive and their replacement by wheel hub motors and batteries. Whereas probably all participants hope for government subsidies, because buses are very important to improve city air. Of course, then would be potential candidates also other municipal establishments such as the waste collection. 07/13