Week 4 History Essay

           The first inventions were gears. What are gears? Gears are round disks with teeth on the edges. Two or more gears are lined up together, and when one is rotated, they all will spin together. We actually do not know who invented them, but an ancient Greek scientist named Archimedes used gears to make a device that tracks the planets. Gears are now used in cars, bikes, clocks, washing machines, and many other things that use a motor.

           The second invention this week was the water wheel. A water wheel is a large, wooden or metal wheel with blades or buckets on the rim. It uses water to turn the water wheel, which is usually connected by a rod to gears. The water turns the wheel, which turns the gears to be able to do some kind of work. This work was usually grinding flour, but it can be used to make other machines work too. It was invented by the Hellenistic Greeks around 200 B.C. It helped people to leave the bigger cities and make smaller communities. They could feed themselves and make different things to live on their own.

           The next day, I learned about the crank and connecting rod. The crank is an arm attached to a rotating shaft, and the rod is attached to the crank. The crank moves in a circular motion, and the rod moves back and forth, like a saw. It could be used with the water wheel and gears to use the circle motion and change it into a back-and-forth motion. It was first used in Chine around 200 B.C., but the Romans used in in sawmills around 400 B.C. Today, the crank and connecting rod are still used in bicycles, trains, and the internal combustion engines of cars.

           Last, I learned about the cam. A basic cam is a shaft with a tooth attached to it. It can be used to make a back-and-forth motion in a machine, like a steam engine. It was invented by the Hellenistic Greeks around 200 BC, but no one really knows who built it first. The Hellenistic Greeks liked to make automaton toys, and the cam helped them do this. Later, along with the water wheel, the cam took over manual labor previously done by humans.

           My favorite invention this week was the water wheel. I like it, because I think it is interesting and cool that people used the river to turn the wheel. I always thought people had to turn it themselves. I also thought it was cool that water controlled all the other machines too.