Parallel grouping of elementary gearboxes
Gear speed reducers

While series grouping enables high i-ratios to be achieved, the overall dimensions, even when optimized, are quite large, and the shape of the casings is highly asymmetrical, especially when the PV torque increases. Parallel grouping attempts to share power and torque in order to reduce dimensions and achieve more compact assemblies. The resulting structural diagram is shown in figure 26 .

The first kinematic law is simple but precise: