Building your own motorized models is a fun educational activity. If you are a Star Wars fan, you may want to check this K’NEX Motorized Walking AT-TE out. You are going to need 818 K’NEX pieces to complete this project. The model can walk in a straight line. It has a big cannon that can rotate 360 degrees. Its other 6 cannons can also move slightly.
The above video shows how this motorized model moves. More information is available here.