An advantage of a pin gear: it can work at the same time as a gear with external and internal teeth.

The orange input crank carries the red pin gear (Z2 = 9 pins) that engages with output green gear (Z1 = 8 teeth) and yellow stationary gear (Z3 = 10 teeth).

i = nc/n1 = Z1(Z3-Z1) = 4

nc: input crank velocity

n1: output gear velocity

If (Z1-Z3) small and Z1 large, i can be very large.

The input and the output rotate in opposite directions.

The pins can be equipped with roller bearings to get a no-sliding speed reducer.