Axles are bars that go through the middle of most wheels. Axles can hold just one wheel or can hold more than one. A skateboard has two axles, with two wheels on each one. Cars have four axles and four wheels.
Sometimes axles have cranks that move around them and help turn them. Pencil sharpeners have handles to turn them. These handles are cranks. Bicycle pedals are also cranks. They both turn the axles inside the machines. Doorknobs are wheels and axles. There is a small axle inside the doorknob, and the large round knob turns around it. The axle is the part that pulls in the latch to open the door.To learn more about axles, visit this site: http://www.factmonster.com/ce6/sci/A0852032.html
