LEVER MECHANISM

PRESENTED BY : VIKNESH.K B.E.MECHANICAL ENGINEERING

LEVER- AN INTRODUCTION

PARTS OF LEVER SYSTEMS

CLASSES OF LEVER

FIRST CLASS LEVER

SECOND CLASS LEVER

THIRD CLASS LEVER

APPLICATIONS

LEVERLevers are one of basic tools that were probably used in prehistoric

times. It is assumed that in ancient Egypt, constructors used the lever to move and uplift obelisks weighing more than 100 tons.

Lever is a simple machine that makes work easier to use; it involves moving a load around a pivot using a minimum force.

A lever amplifies an input force to provide a greater output force,which is said to provide leverage.

The levers are used to lift heavy weight with least amount of effort.

PARTS OF A LEVER SYSTEM

A. Lever E. Effort Arm

B. Fulcrum H. Resistance ArmF. Effort Force

C. Resistance Distance

D. Resistance Force

G. Effort Distance

Entire board

CD

H

GF

B

A

E

Lever – A bar that is free to pivot around a center point (Changes direction and/or amount of force).

Fulcrum – The fixed point around which a lever pivots (fulcrums can take many shapes).

Effort Force – The force applied to a machine to cause motion of an object. (Measured in Newton N)

Resistance Force – The force exerted by an object due to gravity or friction. (Measured in Newton N)

LEVER SYSTEMS

Effort Arm – The part of the lever to which the effort force is applied.

Effort Distance – The length of the part of the lever from the fulcrum to the effort end of the lever. (The length of the Effort Arm.)

Resistance Arm – The part of the lever on which the resistance force is exerted.

Resistance Distance - The length of the part of the lever from the fulcrum to the resistance end of the lever. (The length of the Resistance Arm.)

Contd.,

Lever can provide mechanical advantage by reducing the effort needed to lift the a load.

If fulcrum is closer to the load, then we need lesser effort but load does not move Greater distance.

When fulcrum is closer to the effort, then the load move greater distance , but we need greater effort.

FULCRUM

Lever are classified on the basis of location of effort , load and fulcrum

They are:

First class lever

Second class lever

Third class lever

CLASSES OF LEVERS

FIRST CLASS LEVEREFFORT

FULCRUM

RESISTANCE

FIRST CLASS LEVER

A first-class lever is a lever in which the fulcrum is located in between the input effort and the output load.

• A first-class lever is a lever in which the fulcrum is located between the input effort and the output load.

• In operation, a force is applied (by pulling or pushing) at one end of which causes the lever to swing about the fulcrum, overcoming the resistance force on the opposite side.

• The fulcrum may be at the center point of the lever as in a seesaw or at any point between the input and output.

• The fulcrum supports the effort arm and the load.

CHARACTERISTICS OF FIRST CLASS LEVER

SECOND CLASS LEVEREFFORT

RESISTANCE

FULCRUM

SECOND CLASS LEVER

A second-class lever is a lever in which the resistance is located in between the input effort and the fulcrum.

CHARACTERISTICS OF SECOND CLASS LEVER

• Resistance is located between the effort force and the fulcrum.

• Always multiplies a force

• In a second class lever the input effort is located at the end of the bar and the fulcrum is located at the other end of the bar, opposite to the input, with the output load at a point between these two forces.

THIRD CLASS LEVEREFFORT

RESISTANCE

FULCRUM

THIRD CLASS LEVER

A third-class lever is a lever in which the effort is located in between the input resistance and the fulcrum.

CHARACTERISTICS OF THIRD CLASS LEVER

• For this class of levers, the input effort is higher than the output load, which is different from second-class levers and first-class levers.

• However, the distance moved by the resistance (load) is greater than the distance moved by the effort.

• In third class levers, effort is applied between the output load on one end and the fulcrum on the opposite end.

Mechanical Advantage is the ratio between the load and effort.

Mechanical Advantage deals only with forces.

Mechanical Advantage > 1 means that the output force will be greater than the input force.

(But the input distance will need to be greater than the output distance.)

First and Second class levers have a positive mechanical advantage.

Third class levers have a mechanical disadvantage, meaning you use more force that the force of the load you lift.

MECHANICAL ADVANTAGE

LAW OF LEVER: “The length of the effort arm is the number of times greater than the length of the resistance arm as the resistance to be overcome is greater than the effort you must apply.”

Plugging these into an equation gives you the change in force by using a lever.    Where,L = length of effort arm,l = length of resistance arm,R = resistance weight or force, andE= effort force.

How the Lever changes the Force?

NATURAL LEVERS :

F

E

RTHIRD CLASS LEVER

E

F

R

FIRST CLASS LEVER

ER

FSECOND CLASS LEVER

EXAMPLES FOR LEVERS

CONCLUTIONThe concept of levers has been explained because it is an important one for those

who build robots , especially humanoids

Without lever system it is impossible to lift or move a load.

THANK YOU!