This week we have measured out, cut and assembled most of our sandbox, including the bottom shelf and casters. We decided to model it similar to a shopping cart, two front wheels that remain straight, two rear wheels that rotate and in our case, also lock. This should provide the most flexible, yet stable, build.
Next week, we plan to work on the support structure for projector and XBOX Kinect. We may also benefit from some type of handle(s) to push the cart when moving from class to class, so that's on the shopping list.