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Monks, Beer & Cars, What do they have in common?

Essay #5 History of Inventions 4th Grade

Hi, today I will be talking about gears, water wheels, crank & connecting rods, and cams. All these were discovered before or during the Roman Empire, but they were underutilized at that time.

After the Roman Empire collapsed, in 200 AD, it was monks who brought the people and the villages back up to their feet, because they knew how to read and write and they had books in their library that contained information about these earlier discoveries. They built the water wheels and the cams and the gears and made them popular.

For example, they discovered that water was contaminated with parasites and other microbes, and got them sick, however when they drank beer they didn’t get sick, because beer seem to sterilize the water.

To make beer you have to crush the ingredients, so the monks figured out how to use the cam and the water wheel together and made the “trip hammer” which allowed them to crush the ingredients and make lots of beer with lots of ease.

Did you know this fact? I had no idea, so I think it’s pretty cool.


Gears are usually round objects with little teeth on them, no, not teeth that are in our mouth but rectangular-like objects that stick out of the circle, I may not explain it that well so you can look in the image. Two gears connect to one another with the teeth and rotate each other when you move a lever or when you pedal a bike for instance. Bikes, cars, old mechanical watches, and washing machines, they all use gears. See, there are so many uses for gears, we should be very happy that they were discovered.

But we’re not the only ones that use gears, grasshopper’s legs actually have gears in them. I know right, it’s pretty amazing.

Water Wheels

Water wheels are kind of like bigger gears, well not really but kind of. Invented by Greeks around 200 B.C., water wheels were used for irrigation by Egyptians. The current of the river turned the wheels and water was pushed into the lands were they grew crops. This was a labor saving device, because people didn’t have to carry those heavy buckets with water all the way to the fields, so they could do other activities.
Romans use the water wheel to grind grains into flour and cut stones for construction projects.

Crank & Connecting Rod

The crank was invented by Chinese in the 300 B.C. The Romans knew about it but they didn’t want to use it because of course they had slaves, but after the Roman Empire collapsed in 200 A.D. due to economic pressure, a Roman figured out how to use the crank in reverse by connecting it to a rod, so the crank connected to a rod converts circular motion into linear motion (reciprocating motion) and vice versa.

This new discovery made possible grinding of grains into flour for bread making and feeding many people became much easier. The romans also used the crank and the rod to cut stones in construction. Later they were used in the steam engines, which lead to the industrial revolution. Today they are used in train wheels, and combustion engines.


According to the Oxford dictionary, a cam is a projection on a rotating part in machinery, designed to make sliding contact with another part while rotating and to impart reciprocal or variable motion to it.

The inventor of the cams are unknown but it was most likely invented in Greece, at least we think that. It was a labor saving device, Rome and Greece used slave labor so it really didn’t take off in the Roman empire, but after The Roman empire collapsed it took off. As I mentioned earlier in the article, the monks were the ones who brought this invention back to life by using it to make beer. Overtime the cam progressed and today we use it in cars engines.
This invention most likely lead to the Industrial Revolution.

This was a lot to take in, I know. Anyway, my favorite thing is probably the gear because it is found in grasshoppers legs. What’s yours?

Thank you for reading my article, please share your feedback in the comments below. Bye, and have a nice day.

Reference: history course materials, lessons 16 to 19.


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