id.arts has 3D printed a working replica of a 2-axis rotary jet engine for IHI corporation in Japan. The results of the design, modeling and printing are quite phenomenal, especially considering it was all done within a 2 week time frame. They use motors and remote controls from a company called oriental motors to control the speed of the motors. Read more about this and see a video of the engine in action at: http://3dprint.com/17716/3d-printed-jet-engine/