Gears

The gearing within Graham Farish models is an important component of the mechanism, transferring rotational force from the motor to the drive wheels, and also changing the axis of that rotation, often via a worm, or pinion, gear. See below for three kinds of gear towers found on Graham Farish models.

Small Diesels - click on image for a larger view
The small diesels such as the class 20/25/33/DMU have 2 drive axles, or wheelsets. These clip into the outer two axle slots on the bogie chassis. The next two outer axle slots have stub axles with a knurled centre clipped into them and a 12 tooth gear on each axle. The centre axle slot is home to another stub axle, this time with a 16 tooth gear on it. The top of the bogie chassis is home to a 25 tooth gear on a stub axle with a knurled end. This 25 tooth gear meshes with the pinion (worm) gear, which is not shown on the illustration.
Large Diesels - click on image for a larger view
largedieselgeartower2The large diesels such as the class 37/47/50/52/55/56/57 mostly have 3 drive axles, or wheelsets. The exception here is the class 52 Western, which only has 2. These clip into the 3 axle slots at the bottom of the bogie chassis - for the class 52, they clip into the two outer slots and the middle one is left empty. Moving diagonally up, we see where two stub axles with knurled ends slot into the bogie chassis. These have 16 tooth gears on them. At the top we see another stub axle with a knurled end slot into the bogie chassis, this tie with a 25 tooth gear on it. This 25 tooth gear meshes with the pinion (worm) gear, which is not shown on the illustration.
Class 87/90 - click on image for a larger view
electricdieselgeartower1This gearing mechanism is slightly different to the above two, in that it is not driven by a pinion (worm) gear, but rather by a drive coil, or spring. Again, this is not shown in the illustration. We see two drive axles (wheelsets), which clip into the axle slots at the bottom. Moving from left to right, we see a 16 tooth, followed by a 25 tooth, followed by two more 16 tooth gears, all held in place by stub axles with a knurled end, which slot into the bogie chassis.