*arabic: acbar = unequaled
Using one internal and one external gear small and medium gear reductions can be realized. In case higher gear reductions are asked two pairs of gears are necessary, consisting of internal and external gears. A design, with which the highest gear reductions are enabled, is realized withgears, when the eccentric gear of the propulsion stage is connected with the gear of the output stage. The translation formulas of such gears may vary with different forms.

In the simplest case (A+B) (Acbar classic) the formula may "explode" and end up with extreme values. The closer the number of teeth of the internal and external gear are and the closer the number of teeth of the propulsion stage and the number of teeth of the output stage are the higher is the gear reduction. Inverse gears (in the direction of rotation) and gears with the same direction of rotation are possible. Using a simple design (cases C+D) small gear reductions are possible.

Eccentric gears with two pairs of teeth have many applications in all technology areas. They are compact and high loadable. They may be designed at low cost level for single applications as well as for big series productions.

We have experiences in figuration and design of such gears as well as with toothing software and calculation programs for design and dimensioning of these gears. They may be designed with different toothing types.