Hydraulics and pneumatics

TECHNOLOGY

Grade 6

HYDRAULICS AND PNEUMATICS

Module 16

HYDRAULICS AND PNEUMATICS

Background

Hydraulics is the study of the movement of liquid and the utilisation of its force in the form of mechanical movement. Hydraulics is based on the principle that force can be transferred by a liquid. Hydraulic machines have parts that can be controlled by making use of a liquid under pressure. A hydraulic system contains a pipe that is filled with a liquid such as oil, and a valve/piston that moves to and fro in the pipe. When the liquid in the pipe is put under pressure, it causes the valve/piston to move, which sends the force from one end of the pipe to the other.

Pneumatic systems have parts that can be controlled through compressed air. In a pneumatic system, air causes the piston/valve to move and thus the force is carried over from one position to the other. A bicycle pump and a vacuum cleaner are pneumatic systems because each has a pump that transfers air from one place to another and thus transfers a specific force. In a vacuum cleaner a pump sucks air from an area, and this creates a vacuum. Dust from outside is then sucked into the vacuum in order to fill the area.

If we have to move heavy objects by making use of a compressed liquid we use a ____________system. Extremely powerful machines that can press, push or lift, operate hydraulically. A hydraulic system greatly increases the force that an object exerts.

Movement is controlled by making use of a liquid where levers and cables would be inadequate.

ASSIGNMENT 1:

To make a simplified hydraulic pump

[LO 1.3]

Requirements:

A plastic tube more or less 40 cm long

Adhesive tape

A heavy object

Water

Two large balloons

Two 2 ℓ plastic bottles

Two rubber bands

A pair of scissors

A funnel

Two empty cool drink tins

Method:

Put the open end of the balloon over the end of the plastic tube and seal it with adhesive tape.

Cut off the top part of each bottle just above the labels.

Make a small hole close to the bottom, near the base of each bottle.

Push the balloon and the plastic tube through the hole of bottle B.

The balloon must lie on the bottom of one of the bottles.

Push the other end of the plastic tube through the opening of bottle A. To fill the balloon in B, carefully pour water into the tube by using the funnel. Fill the other balloon with water and fix it to the plastic tube in A, as in step 1. Try to leave as little air as possible in the balloons and the tube.

Place the tins in the bottles on top of the balloons. Then carefully place the heavy object on top of the tin in B.

7. Now press hard, but carefully, on the other tin in A.

What are your observations?

More water is forced from the balloon in A to the balloon in B. This pushes the tin upwards, which then causes the heavy object to be pushed upwards as well.

Why does it work?

It is difficult to compress water. When you put water under high pressure in one place, it will flow out with the same force elsewhere. The water therefore transfers the force from one tin to the other. All hydraulic machines work on this principle.