How Do Gears Work

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All About Gears that Everyone Should Know

Gears or Cogs are in just about everything containing a spinning part, that is, from cars to clocks. Car's transmissions and engines contain lots of cogs that help in reducing the gear in motorized equipment. There're other lots of important jobs performed by these simple machines; however in this article, people will be enlightened on the history, works and the applications of cogs.

The History of Gears

History has it that cogs were first used by Greeks in clocks and water wheels around 3rd century B.C. However, a clear origin of these simple machines can be traced back to a vehicle that was allegedly engineered by Ma Jun, a Chinese mechanical engineer, in the 27th century B.C. The chariot was built on two wheels, and it bore a movable indicator that was mechanically geared to face towards South only, no matter how much the vehicle turned. It is believed that no further discoveries on cogs were made until the 17th century when scientists attempted to provide constant velocity ratio of cogs.

It was in the 19th century that rotating cutters and form cutters were introduced in the market, through the help of an English inventor, Whitworth, who patented the first gear hobbing process in 1835. Later in 1897, Herman Pfauter of Germany introduced the first hobbing machine capable of cutting helical and spur Cogs.

The 20th century saw the development of various types of machines. However, the major development came in 1975 when a Germania company called Pfauter introduced the first NC hobbing machine, which later birthed the invention of a full six axis machine.


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How Do Gears Work

A gear is a wheel with teeth, sometimes known as a cog, whose job is to transmit power from one machine's part to another in order to accelerate or decelerate speed, increase force or change the direction of a machine. To be able to work with this simple machine, at least two wheels must have their teeth locked into each other. Since teeth fit together, when on wheel turns, the other turns too.

Thinking of cogs as wrenches paints a good picture of how they operate. When a person pushes a wrench at point A to unfasten a nut at point B, then point B would turn at a slower speed and more force than point A. That's what is expected when two cogs are fitted into each other, where one is bigger than the other.

When a big cog is connected with a small one, and it's turned slowly, the big wheel will make the little cog to rotate quickly. Turning the big cog slowly will require less energy than it would to rotate the small one quickly; so by using cogs, there is saving of energy and making work easier.

It's also possible to increase the speed of a machine using cogs that have a different number of teeth. What happens is that when the big wheel is turned, then the little wheel has to rotate much faster to keep up but with less force.

When two cogs slot into each other, the second normally turns in the opposite direction. This means that when one rotates clockwise, the other turns anticlockwise. This arrangement is used to turn the power of a machine through an angle.

Why Gears Are Needed

Cogs are basically used to do the following task:

  • Changing the direction of rotation
  • Increasing or decreasing the rotation speed
  • Increasing force
  • Keeping the rotation of two axis synchronized
  • Measuring time

Some of the machines used in our daily life would be impossible to operate without cogs. A car is a perfect example that has a box full of cogs. So why are cogs needed in there?

The car's engine works best at a minimum speed of about 1000 rpm, meaning if the speed go below that, then the engine would cut out. With that ideal speed, it would turn out to be a problem if the engine was directly connected to the wheels, as that would mean that the wheels would have a minimum of 1000 rpm as well such that when the car is ignited like this, the wheels would instantly spin at 120km/h.

The problem of having the engine directly connected to the wheels is that lots of force would be needed to get the car moving from a standstill. Similarly, an engine will be unable to generate enough force to bring itself to stop speed. To get a car moving, a driver will need to engage a low gear in order to generate a large amount of force and little speed. So, cogs reduce the engine's speed while at the same time, proportionally, increase its force to get a car moving.

Although this is not an exhaustive list of why gears are needed, it can be easily seen that gears are vital part of many things pertinent to everyday life.  



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