What to do with a bucket of wheels?

When I was cleaning out my basement I found a bucket of old wheels.  I decided to bring them to school to see if the children could come up with a use for them.  The children explored and played with them several times.  They decided each child should get their own wheels to make something with.  Before the break, the children drew up sketches and gave me a list of materials they would need to complete their creations.  Upon their request, I brought in boxes, duct tape, electrical tape, batteries, and hot glue guns.  

Arwyn's plan

Some children stuck with their plans, while 
others improvised as they made discoveries about what worked and what didn't.  Here are a couple of examples of the finish products.

The final product a mobile cat bed

Andrew's car

 

A catapult  by Andrés