Complex Machines

You have already known about the six simple machines: inclined plane, wedge, screw, lever, wheel and axle, and pulley. You've probably figured out that these six machines were invented ages and ages ago. So what has been happening since then? Did someone invent simple machine number 7, 8, 9, 10, and so on?

Let’s look at a bicycle for an example. A bicycle is a much newer machine than the simple lever that a cave man used to move a big old rock, but it’s not as new as, say, a laptop computer. A bicycle is not number 7, or 100, or even 1000. A bicycle is actually a combination of several of those six basic simple machines. A bicycle gear is actually a combination of simple machines all by itself. A gear is a wheel, but the teeth on the gear are little wedges. What other simple machines can you find on a bicycle?

Gears, along with other simple machines, make up many of the machines you use every day. Some examples are the lawn sprinkler, a watch, and the gearbox in a car. Escalators and elevators use combinations of simple machines. So does a hand drill. So do sewing machines, parking meters, and windmills.

The doorknob is a wheel and axle system that transfers the force applied by a person to a system of levers. The levers move the bolt and unlatch the door. A pair of pliers is really two Class 1 levers with the same fulcrum (the pivot pin). A pair of scissors is a pair of pliers with wedges as the cutting edge.

Machines that use a combination of two or more simple machines are called complex machines. Machines can do all kinds of jobs today and make our lives easier in many ways.

Some complex machines are very complicated. An automobile is one such machine. The engine contains many levers, wheels and axles, and pulleys. The whole engine is held together by threaded bolts, which are a form of inclined plane. The transmission uses gears, which are a form of wheel and axle with specially shaped teeth on the outside of the wheels. Two gears fit together and transfer force and power from one gear shaft to another. By choosing the size of the gears, the speed and direction of the rotation of the axles can be controlled.

Even devices that do not seem to be mechanical use simple machines. A computer, which is thought of as an electronic device, has a cooling fan. This fan is a complex machine in which the motor shaft turns the fan, which is a form of wheel. The disk drive uses a wheel and axle to turn the disk and a system of levers to position the heads that read and write the data on the disk.

Дата добавления: 2015-10-21