Levers

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In this presentation you will: identify the use of levers in hydraulic applications

Levers

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In this presentation you will see first, second and third class levers.

You will also see hydraulics applications where levers are used.

Levers

Mechanical Levers

Levers are simple mechanisms used to apply mechanical advantage.

A lever can be a long bar that rests on a pivot point (fulcrum). An effort is applied to move the load.

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For example, by using a stiff branch resting on a log, early man was able to lift heavy rocks.

Levers

Lever Classification

There are three classes of levers. They differ in the placement of the fulcrum, effort and load along the lever.

First class lever

The three types are:

First Class

Second Class

Third Class

Second class lever

Third class lever

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Sometimes these are also referred to as first order, second order and third order levers.

Levers

1

The lever shown is a:

Question

A) first class lever

B) second class lever

C) third class lever

Levers

First Class Lever

A mechanical advantage of force is achieved if the distance between the effort and fulcrum is longer than that between the load and fulcrum.

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The lever will balance if the load and effort are equal, and they are also both the same distance from the fulcrum. The system is in equilibrium.

First class levers are the most common type of lever. The fulcrum is between the effort and the load.

A seesaw is an example of a first class lever. Other examples are a claw hammer, crowbar, scissors and weigh scales.

Effort

Fulcrum

Load

Levers

Second Class Levers

The load is between the effort and the fulcrum. Second class levers provide mechanical advantage of force, as the effort is always further away from the fulcrum than the load.

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This allows a large load to be lifted a small distance by a smaller effort moving a larger distance.

A wheelbarrow is an example of a second class lever. Other examples include bottle openers, foot pumps and nut crackers.

Small effort,large distance

Large load,small distance

Levers

2

In a second class lever, where should the effort be placed?

Question

A) On the opposite side of the fulcrum to the load

B) On the same side of the fulcrum as the load, but further away from the fulcrum

C) Between the load and the fulcrum

D) On the opposite side of the fulcrum but very close to it

Levers

Third Class Levers

This means the effort force needs to be larger than the load, but with the advantage that the load moves a greater distance than that moved by the effort.

The effort is applied between the load and the fulcrum. The effort is closer to the fulcrum than the load.

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An engine hoist is an example of a third class lever. Other examples are tweezers and fishing rods.

Effort

LoadFulcrum

Levers

3

Which of the following is an example of a third class lever?

Question

A) Wheel barrow

B) Scissors

C) Fishing rod

D) See-saw

Levers

Hydraulic Systems Using Mechanical Levers

Many construction machines make use of the hydraulic lever principle, whether they are excavating, lifting, grading, or drilling machines.

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An excavator uses a hydraulic cylinder to push up the boom, but the boom is itself a type of lever. A short movement of the cylinder makes the end of the boom move much further.

First class lever Third class lever

Levers

4

On an excavator, what part of the lever mechanism does the cylinder represent?

Question

A) Load

B) Effort

C) Fulcrum

D) LeverCylinder

Levers

Summary

You should now be aware of:

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Examples of levers in hydraulic systems

Different classes of lever