7. Mixed compound groups

Series grouping is required when the transmission ratio becomes important. Parallel grouping is of interest when low-speed torque increases and you want to reduce dimensions. It is therefore possible to imagine mixed groupings such as those shown in figure 33 :

• on figure 33 a, an elementary coaxial gearbox with an intermediate shaft followed by two fixed-ring planetary gear trains with three planetary gears ensures a limiting reduction ratio of the order of 1,000, using coaxial shafts;

• on figure 33...