My goal is to engage elementary school children to be curious about the world around them, and I think this simple cam & follower car engine is a great example.

This is the one I wanted to build for over a month, but I didn't have the parts. When I ordered the cam parts (LEGO apparently calls the part comb wheels, and I don't get the connection), it took THREE weeks to get to northern California. I guess it's understandable since they were coming from England.

Step 1: List of Parts

Step 2: Building the Pistons

Step 3: Building the Legs

Step 4: Putting the 1st Gear In

Step 5: Cam Build

The hardest part of building this cam was to put this long piece with a flat end (right hand side) through the red technic piece (left hand side) AFTER assembled the legs already.