Hydraulics and pneumatics  (Page 2/2)

Background

Powerful bulldozers, fire engines and cranes use hydraulic power to lift heavy loads easily. A liquid is carried from a pump by means of pipes to cylinders where the liquid pushes valves/pistons out with great force. The pistons force the shovel into the soil and a heavy load of soil can thus be lifted. (A valve causes air or a liquid to move in one direction, but also prevents air or water from flowing back again.)

The advantage of making use of air pressure is that air is clean, freely available and safe under low pressure. Under high pressure air can be very dangerous. By nature air is resilient and this can cause a problem

Hydraulic systems are sometimes better than pneumatic systems because motion can be obtained more easily. When a leak occurs in a hydraulic system, it could be very messy.

ASSIGNMENT 2:

To investigate a hydraulic and pneumatic system

[LO 1.3]

Requirements:

Two syringes of equal size.

A plastic tube of about 10 cm that will fit tightly over the opening of both syringes.

Method:

Draw out the plunger (piston) of one syringe and push in the plunger of the other syringe.

Connect the two syringes by means of the plastic tube.

Push in the plunger of one syringe.

Draw that plunger out again.

Observation

When one of the plungers is pushed in, the plunger of the other syringe is pushed out by the same distance. When the plunger of the one syringe is pulled out, the piston of the other syringe is sucked in by the same distance in the tube.

ASSIGNMENT 3:

To replace air with water or oil

[LO 1.3]

Question:

How do the syringes that are filled with water compare with the syringes filled with air? Which system works best?

Underline:

The pneumatic/hydraulic system works better.

ASSIGNMENT 4:

To investigate the effect of syringes of different sizes on each other

[LO 1.3]

Method:

For example, connect a 10 ml syringe to a 20 ml syringe.

Push in the plunger of the small syringe and observe how many mm the plunger of the big tube moves out.

Also pull the plunger of the small syringe out and observe how many mm the plunger of the big tube moves in.

Underline:

When a small cylinder has half the volume of a big cylinder, the plunger of the big cylinder moves (half/quarter of) the distance of what the small cylinder moves.

The force exerted by the big cylinder is (less/more), namely half as much (more/less).

ASSIGNMENT 5:

[LO 1.3]

Now connect a big syringe with two smaller syringes, for example a 20 ml syringe with two 10 mm syringes by using a T-joint connection. The plunger in the big syringe must be pulled out and the plungers of the smaller syringes must be pushed in.

Push the plunger of the big syringe in and observe how many ml the plungers of the

smaller syringes move up.

Now push in the plungers of the smaller syringes and observe how many ml the plunger of the big syringe moves up.

Underline:

Because the smaller syringes together have the same volume as the big syringe, their plungers move up (half the/the same) distance as the plunger of the big syringe when it is pushed in.

The force that is exerted in the big syringe is (a quarter/half) less in each small syringe.

Background:

In industry cylinders are used to perform the same tasks. If a pneumatic cylinder must be used often, a compressor with a control valve is used to let air into the cylinder. The cylinders are mechanically connected to the tube with an attachment and to the syringe with a pivot.

Assessment