This little unit I made out of found objects. The tank is from a used fire extinguisher, the handle is from a lawn mower, the handle grip is from a weed eater, and the motor is from an in-window air conditioner. Add some gauges and fittings and you got an air compressor!
The most important feature of this unit is the compressor. It isn't loud like a traditional air compressing motor. It's like listening to your fridge run.