This is rail car number three in what (I hope) will be a series of ten, one published every two weeks until Christmas. This O gauge car (wheels, axle, coupler and bed are all 3D printed plastic) is part of an active train. It requires a drinking bird (available on amazon.com) and 4 AA rechargeable batteries, along with a 10 ohm 3 watt resistor (http://www.digikey.com/product-detail/en/PNP300JR-73-10R/10AECT-ND/2059154)
Print the wheels and bed.
Secure the bed to the wheels with the bed caps.
Insert the bird.
Add the 10 ohm 3 watt resistor. Solder the wires from a 4 cell AA battery holder to the resistor.
Glue the battery holder to the rail car's bed. Insert the batteries when you want the bird to operate (takes about one minute to warm up and get started).