ROTWILD Integrated Power Unit (IPU)

Schematic drawing IPU – Integrated Power Unit by ADP Engineering, Pat. Nr. DE 10 2014 218 036.8

The ROTWILD IPU consists of a Brose drive motor and the battery unit developed by us. The aim in development was to integrate the two elements completely within the bike frame in order to retain the dynamic riding characteristics (geometry and kinematics) of classical mountain bikes. The system of the IPU has been registered as a patent with the European Patent Office under Reg. No. DE 10 2014 218 036.8.

Schematic layout Brose pedelec electric motor

BROSE motor unit forms a particularly suitable basis

The pedelec electric motor developed by the German automotive supplier BROSE forms the basis for our IPU. In electrical engineering terms, it involves a “brushless internal rotor”, which is characterized by an extremely compact design combined with high efficiency. The power from the electric motor is transmitted in two stages in a ratio of 1:27. In the first stage, a planetary gear with a transmission ratio of 1:9 is connected before the motor while transmission in the second stage takes place in a ratio of 1:3 via a belt drive. This transmission ratio is necessary so that the electric motor (driven by the rider’s relatively low pedalling frequency) always rotates within its optimum speed window in order to guarantee a high efficiency. This means that the electric motor always rotates within its optimum window of revs, guaranteeing high efficiency. Another unique design feature of the Brose motor is the use of two freewheel mechanism in the interior. This is very important in the case of pedelecs with a legally prescribed cut-off speed at 25 km/h. With the aid of the second freewheel mechanism, the electric motor disengages entirely once the 25 km/h limit has been exceeded so that the rider can continue to accelerate the bike with muscle power and without any loss in forward drive.

Brose has continued to optimise the motor in the new Brose Drive S (available from MY 2018). The increased efficiency and the new thermal design increase the power output. The torque curve has been specially adapted for use in sport and the responsiveness has been improved for technical terrain so that uniform support is always provided and everywhere becomes accessible by bike.

Schematic drawing of the IPU – housing shell

Battery designed in collaboration with a German battery producer

We designed the battery unit in collaboration with a German battery producer. Essentially, the battery consists of four basic elements: the 40 Li-ion cells, the battery management system (BMS) with cable harness and motor connector, the integrated charging socket and the housing that encloses and protects the entire battery unit.  

Two different batteries are offered as of the 2018 model year:
The IPU.500.ALUMINIUM has a total capacity of 518 Wh. It is completely integrated into the aluminium bottom tube and is permanently installed in the frame. The battery consists of 40 lithium-ion cells (model INR18650 MH1), divided into 4 packs of 10 cells. Each cell provides 3,600 mAh. The IPU.500.ALUMINIUM will be used in all CORE models as standard. The IPU.R.660.CARBON has a total capacity of 648 Wh. The battery is integrated into a carbon bottom tube, is removable and can be charged both on and off the bike.

The IPU.R.660.CARBON has 50 premium lithium-ion cells (model 18650), where each cell provides a voltage of 3.6 volts (ranging from 4.2 to 3.6 volts) with a capacity of 3,600 mAh. What makes these lithium-ion cells special is their inner chemical make-up which was specifically designed for use in electric bikes and the automotive industry. The IPU.R.660.CARBON will be used in all Ultra and Pro models as standard. The IPU.R.660.CARBON is backwards compatible and can be integrated into all ROTWILD/Brose hybrid models. 

IPU integration into various bicycle designs

Our IPU is designed in such a way that we can use it in all bike categories or ranges without any great restrictions in geometry, kínematics or compatibility, i.e. from ROTWILD MTB Cross Country via All Mountain to Enduro; yet at the same also in the multifunctional Tour or Trekking Bike sector. To this end, the motor housing becomes a permanent part of the frame, firmly bolted to the bottom tube battery and unit and the frame – the bottom tube battery unit becomes a supporting element within the frame structure. The compact design additionally enables us to achieve short chainstay lengths or appropriately position the pivot points which are important for the development of full-suspension frames.

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