Thanks everybody for nice comments
In order to attach the drive properly, I had to grind down a slight edge so that the gear in the gearbox went free.
Here it would have been a little more pictures but sometimes when things go well you forget

In all cases the drivesystem are now fully assembled.
Therapy work

two of these,
one of this
and one of this
and the rollers are done.
Suddenly all 24 done.
Drivesystem mounted on chassis.