The HettlageVariator is the core part of a gear drive for tooth belt or chain transmissions providing an outstanding degree of efficiency. The gear can be shifted under full load and is based on a variable sprocket. It was developed in several builds for a variety of applications.



A variable sprocket is able to take the form of sprockets of various circumferences. Based on this concept the HettlageVariator can replace the gear cassette of a chain drive or the internal planet set of a gear hub.

The HettlageVariator is set up on a base disc that is mounted to the propelled axle. The base disc has radial slots, each equipped with a slide. Each of theses slides has a segment of a sprocket at the front of the base disc. The backside of each slide is equipped with a notch mechanism that locks into fixed radial positions.

These positions were defined for the segments to result in a sprocket that matches the tooth belt or chain used for transmission.

When shifted, the segments are moved to a different radial position to form a larger or smaller sprocket. This shifting process is done sequentially for each segment when it is not in touch with the chain or tooth belt. After one rotation of the variable sprocket the shifting is complete.

The shifting and notching of the segments is done by a specially engineered shifting unit that is mounted to the axle next to the base disc. Unlike the latter the shifting unit is fixed. It is attached to a frame. The gear shifting is controlled by a shift cable.

The shifting process being done in the part of the sprocket that is not looped by the chain or tooth belt allows the HettlageVariator to be shifted when the drive section is under full load. Also the HettlageVariator does not require a freewheel clutch as for instance a gear hub does.



Bicycle transmission

The HettlageVariator is available as a gear drive for bicycles with a tooth belt or chain transmission.
It can be used in most customary bicycles. Although for using a tooth belt transmission the chain stray has to be split (as is the case in a four joint suspension). Similarly to gear hubs the HettlageVariator can be integrated completely to the hub of the rear wheel. It merely needs one attachment to the frame. This way demounting the rear wheel is exceptionally simple.
Bicycle transmissions with HettlageVariator have an outstanding degree of efficiency.
Photos of the bicycle drive »
Orders or quote requests for the bicycle drive »


Wind powered vehicle

In a wind powered vehicle that is developed by the Institute of Aircraft Design (ISD) of University of Stuttgart the HettlageVariator is part of the transmission system. The turbine driven Ventomobile is able to drive upwind. The student team involved in the developing of the vehicle has attended international competitions with great success.
To be able to shift gears with the turbine under full wind the HettlageVariator provides a perfect solution. A motor bike chain is used to withstand the enormous force (up to 5 kW) that the wind puts on the transmission system.
Photos of the Ventomobile »


Besides the applications mentioned above the HettlageVariator can be used in any kind of light weight motor powered vehicles.

The numerous different possibilities of application for the HettlageVariator have not been explored yet. If you are interested in using the transmission system for your own purposes, please contact engineer Eckart Hettlage: eckarthettlage@yahoo.de.



HettlageVariator is being sold as a bicycle drive in collaboration with RIGO GmbH. Mountain bikes of the manufacturer Focus equipped with the HettlageVariator. and 29" wheels are available. Alternativiely the bicycle drive can be supplied as a seperate component upon request.

For orders or quote requests please contact:

Mr Rüdiger Golz
+49 7042 83 18 12



Consulting Engineer
Eckart Hettlage

Ostlandstra├če 12
D-77933 Lahr

+49 176 610 529 76