We just learned about the big long spinning pole called the Shaft.
Another part of machines is an Axle.
An axle is a long spinning pole like a shaft, but it is connected to wheels on either side.
It is also usually used to help hold up something like a car or a train.
Sometimes the axle doesn't spin but the wheels do, kind of like on a bike.
When a bicycle's wheel spins, the metal post inside the wheel does not spin.
This is usually called a spindle instead of an axle.
Cars and trucks are sometimes talked about by how many axles they have.
This really means how many sets of wheels across from each other are there.
So a normal car would be 2 axles, but a big semi truck might have 5 or more axles on it to help spread out the weight carried by each axle.
Sometimes they have more than one set of wheels on an axle to help hold the weight, but that still only counts as one axle.
(from: wikipedia - axle)Kid Facts - Blast from the past: Inertial Measurement Unit (IMU)
