A circle is a plane figure bounded by one line, and such that all right lines drawn from a certain point within it to the bounding line, are equal. The bounding line is called its circumference and the point, its centre.
— Euclid, Elements,
In a quiet moment it struck me that without the circle we'd be stuck. As gear(circle derived) heads we would have no cars to be gear heads about. It is impossible not to have a circle but defining it and making use of it affects every aspect of our lives, as well as cars.
Every car design makes use of curves (part circle of differing diameters) except of course the Aston Martin Lagonda.
The gears can be described as epicyclic, cyclical and more, have planetary gears, have a cycloidal drive to name but a few.
Everything is related to a circular movement. The pistons go up and down, or to and fro in a boxer engine, transferring it to a rotational movement of the crank, through the gears to a diff which drive the shafts which rotate the wheels which pushes the Agera RS to warp speed.
The next time you do something, doesn't have to be car related, see how many times a circle or part of a circle is involved or can be used to describe what you are doing.
Now, I'm going to get in my car...open the door ( forms an ARC) get in, push the ROUND start button, look at the CIRCULAR dials ( including the REV counter) into GEAR, ROTATE the steering WHEEL.........and head off to the NurburgRING.
"The circle has been known since before the beginning of recorded history. Natural circles would have been observed, such as the Moon, Sun, and a short plant stalk blowing in the wind on sand, which forms a circle shape in the sand. The circle is the basis for the wheel, which, with related inventions such as gears, makes much of modern machinery possible. In mathematics, the study of the circle has helped inspire the development of geometry, astronomy and calculus."