Frequently asked questions about TheWheel®
To make the principles of our traction system as clear as possible some frequently asked questions are listed below.
Q: Why install a motor in the wheels of a vehicle
A: Because a direct-drive has to provide enough torque to drive a vehicle without gears - and needs a larger diameter to do so. Integrating direct-drive into a vehicle will take considerable in-vehicle space.
Q: How much fuel can be saved with TheWheel®?
A: This depends on battery buffer size and application. TheWheel is very efficient and enables prolonged battery operation. On most of our bus trips, the Diesel APU will turn on after 3 hours of battery depletion. Whenever the generator is used, we reduce diesel consumption by roughly 50%.
Q: Is regenerative braking the key to the high efficiency?
A: Regenerative braking helps getting a vehicle more efficient. However, the key to high traction efficiency is the absence of a gear box. Because of this high efficiency the diesel generator necessary to charge onboard batteries can be much smaller which reduces fuel usages and enables the possibility for lower vehicle weight. All these factors make the e-Traction system highly efficient.
Q: The motors are close to the road. Is there danger for shocks and / or water ingress?
A:TheWhisper is now driving for 4 years with our city bus with the electronics fitted inside of TheWheel. Shocks and water have till thus far never been a problem.
Q: Do you have to remove the motor when there is a flat tyre?
A: No, the tyre is mounted on a rim and the rim is mounted on the outside of the motor. In the event of a flat tyre the vehicle operator can remove the tyre and rim and replace it or repair it.
Q: What type of hybrid is the e-Traction Whisper bus?
A: The Whisper is a plug-in series hybrid. The propulsion of the city bus is fully electric by means of two wheel motors powered by a lithium-ion battery. This battery is charged by a power source, such as a diesel generator within the vehicle. Charging by grid is possible if the vehicle is not in operation. This may also be at a bus stop! See our Hybricon project; the busses in this project will be charged by means of a pantograph system (100% electric operation)
Q: Does higher unsprung weight affect a comfortable ride?
A: Total weight of the unsprung parts (wheelmotors, rims ,tyres and axle) are only 20% heavier than the unsprung parts (wheels, rims, tyres, axle housing, axles, differential) of a normal city bus. Passengers of the Whisper buses are very positive about the comfort of the bus because of the silence and smooth operation as there are no gear shifts. Comfort is therefore at a higher level than normal buses.
Q: What types of batteries are being installed in the Whisper bus?
A: Valence batteries are chosen because of their high reliability, great bms system and for safety reasons. In our Whisper project, 30 u27-12xp batteries of 130Ah are used. In project NEMS, buses will be delivered with 60 u27-12xp batteries.
Q: Why not use Boostcaps in your projects, such as Whisper?
A: At this stage there is a pack of 30 lithium-ion 12,8volt 130Ah Valence batteries onboard The Whisper. These batteries can absorb all the energy coming from the wheels during normal brake action. For emergency stops mechanical brakes are used as these are required by law. Besides, longer lasting battery power is needed to drive zero emission which the boostcaps can't provide.
Q: Do the diesel engines of the Whisper project meet the emission regulations of the U.S or EU?
A: The diesel engines meet the emission regulations of the EU.
Q: Why is a diesel engine generating the power for the battery in the Whisper project?
A: At this moment a diesel engine has been chosen due to requirements on easy handling and infrastructure of bus operators. Nevertheless, any power source is sufficient as long as it can deliver 35 kW to the batteries.
Q: Can other technologies be used for charging the batteries of your Whisper project?
A: Yes every power source can be considered to supply power to batteries of e-Traction vehicles. As long as it supplies 35 kW (in case of a city bus) The Hytruck (small distribution truck) which is fitted with our wheels features a hydrogen stack to supply the power but other power sources can also be used.
Q: Can the batteries of your buses be charged at the grid?
A: Yes, the e-Traction system is actually a full electric plug-in hybrid which means that it can be charged at the grid. The buses will be charged at night so the vehicle operator can use as much 'green' produced electricity as possible. The aim is to use the generator as wise as possible and end the day with an almost empty battery.
Q: Steering by controlling the speed of the motor?
A: The Whisper buses already have a software differential that helps to steer the bus actively through a corner. Regulations prohibit the steering of a complete vehicle on software instead of mechanically.
Q: Can I retrofit my own car with the e-traction Wheels?
A: Currently e-Traction is focusing on OEM's in the truck, bus and heavy duty vehicle market and larger SUV's to proof the viability of its invention. Customizing a single small vehicle is an intensive engineering job, financially unattractive and will probably cost twice the original vehicle price.
