Response to the interview with Lutz Scheffer: “It’s not just the weight that counts – it’s the handling too”

Bike designer Lutz Scheffer is calling for a radical change in regulations: rather than limiting the wattage of electric motors, the motor’s weight should be the deciding factor. Lutz considers the 750-watt limit called for by Bosch to be nonsense anyway. In the >> Interview with Lutz Scheffer << These points are discussed in detail.

Now Ernst Brust, an expert in micromobility at Velotech.de, has spoken out. He says: “It’s not the wattage that matters – it’s the handling.” In this respect, he does not initially contradict Lutz Scheffer; after all, he, too, is opposed to the aforementioned 750-watt limit.

However, whilst Scheffer proposes a maximum engine weight as the solution, Ernst Brust considers a more multifaceted approach to be ideal. Among other things, he regards acceleration and handling as crucial factors. Here is his view.

Here is the presentation by Ernst Brust, an expert in micromobility

​It’s not the power, but the acceleration that counts, says Ernst Brust

A vehicle’s driving dynamics are not determined by engine power alone. Rather, the following factors are crucial:

• the vehicle mass,
• the total mass of the driver and the vehicle,
• the power-to-weight ratio (W/kg),
• the maximum acceleration,
• braking performance and
• driving stability.

A 30-kilogram cargo bike can be safer to ride than a significantly lighter pedelec with an aggressive motor setting. Weight alone is therefore not a suitable criterion.
Ernst Brust, micromobility expert

​Acceleration can be measured objectively

Acceleration has been measured in the automotive sector for decades – both when pulling away and when braking. These measurements can be carried out in a reproducible manner on test benches and during road tests.

Setting a limit on maximum positive acceleration would make far more sense than a rigid wattage limit. It would reflect actual driving behaviour and would be independent of the engine power or engine design used.

Tuning is not prevented by higher wattage figures

Tuning is already a significant problem today. However, raising the permitted engine power limit would not prevent tampering. What is far more important is:

1. effective tamper detection,
2. consistent market surveillance,
3. better controls,
4. clear diagnostic data and
5. practical testing methods.

The vehicle as a whole must be taken into account

The discussion must not focus solely on the motor. A safe pedelec is an integrated system:

1. Frame,
2. Fork,
3. Training wheels,
4. Brakes,
5. Tyres,
6. Engine,
7. Battery,
8. Software and
9. Chassis

must be assessed and tested together. Only by testing the complete vehicle in its ready-for-use state can the actual stresses encountered in road traffic be accurately reflected.

Science rather than speculation

Any new regulations should be based on objective criteria. These include, amongst other things:

1. maximum acceleration,
2. Power-to-weight ratio (W/kg),
3. Braking deceleration,
4. Driving stability,
5. Energy consumption (Wh/km) and
6. Long-term durability of the entire system.

These parameters can be measured in a reproducible manner and allow for a technically sound assessment.

Conclusion

A discussion about the future of the pedelec is necessary. However, a blanket increase in the power limit to 750 watts neither solves the problems associated with tuning nor does it automatically improve road safety.

Instead of a higher wattage, you should objectively measurable criteria such as acceleration, power-to-weight ratio, braking performance and testing of the complete vehicle be at the heart of future regulation. This is the only way to ensure that innovation, road safety and the nature of the pedelec as a bicycle can be reconciled in the long term.
Ernst Brust, micromobility expert and founder of Velotech.de