The Clockwork Engine is an excellent alternative to other early-game power sources. It will output between 0.5 and 1.5 MJ/tick depending on how much it is wound. Right-clicking on the engine block will wind it, and as the engine works, it will gradually lose tick strength.
The Clockwork Engine has no GUI. To wind the engine, simply right-click on the block in the world. The piston will pause moving while you wind it, allowing you to see the current state of the engine.
The positions of the Copper Gear and Clock may be swapped.