To drive the crankshaft of my z-scale Shay locomotive I had limited choices to select a very small, but relatively powerful and reliable motor. One of the major problem with small pager motors, they run on 1.5 - 3V DC power. In the case of Shay, if my goal is to make the crankshaft working only, the 3V motor works just fine. But I have the head light already installed, the rear light is ready to be in place, and the main motor to move the Shay, a very powerful  8 x 10 mm  9V DC motor need to be powered too. There are different methods to reduce the 9V DC to 3V, but there are a few more issues. One is the pulses of the controller, the other is the protection of the small motor. It's a very painful operation to replace this 4 x 5 mm motor in the similarly small gearbox if the motor burns down from overload. So here is the perfect solution, three identical motors are connected in line. There is absolutely no problem with the 9V peak pulses, and in the case of overload, one of the motors without load ($1.50) will work as a fuse and burn out to protect the hard working motor in the gearbox. I've tested the concept and it's proven. The three test motors were running continuously on 9V pulse power  for several days to prove their reliability. Also as seen on the photos, one motor had to deal with some friction, as the shaft was spinning in the fairly tight hole in the side of the plastic box. Now, another positive result (even conclusion) of this concept, if the small pager motors are built into small independent trucks, relatively easily, various, two truck, two motor powered really small locomotives can be achieved.