Levers 2015

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    PRESENTED BY

    SANJAY KUMAWAT

    DESIGN OFLEVERS

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    WHAT IS LEVER

    A lever includes a stif structure (the lever)that rotates around a xed point called theulcrum.

    OR

    A Lever is rigid rod or bar capable o turningabout a xed point called ulcrum

    U!" A A #$% &O L'& LOA" * #ALL

    !OR&.

    fulcrum

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    ANATOMY OF THELEVER

    Lever + A bar that is ree to move about axed point

    ,arts o a lever

    ulcrum +&he xed point o a lever

    !fort Arm +&he part o the lever that theefort orce is applied to (measured rom

    the ulcrum to the point at -hich the orceis applied)

    Resistance Arm +&he part o the lever thatapplies the resistance orce (measured

    rom the ulcrum to the center o the

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    ANATOMY OF THELEVER

    Levers may be straight or curved

    Forces applied on the lever parallel or inclined

    Effort arm load arm

    Large load- small effort i.e. l2should be effort arm and it should

    be greater than l1.

    Large effort arm may not be possible due to space limitations.

    For greater leverage compound levers (straight pieces with

    pins

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    APPLICATION OF LEVERS IN ENGINEERINGPRACTICE

    Three Classes of LeversFirst Class f!l"r!#

    $et%ee& I&'!t a&( o!t'!t

    Se"o&( Class ) o!t'!t$et%ee& f!l"r!# a&(

    i&'!t Thir( Class ) i&'!t

    $et%ee& f!l"r!# a&(

    o!t'!t

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    FIRST CLASS LEVERS

    FIRST CLASS LEVERS ) *SEESAW+ LEVERSst%lass Lever /&he ulcrum is located bet-eenthe efort arm and the resistance arm.

    irst class levers can multipl0 orce and distance

    !xamples1 scissors2 see/sa-2 hammer3s cla-s2 pliers2 etc4

    L2 effort arm > L1- load arm

    Mechanical advantage is more than one

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    FIRST CLASS LEVERS

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    SECOND CLASSLEVERS

    ,ND

    CLASS LEVERS ) *WHEEL-ARROW LEVERS+5nd%lass Lever / resistance is located bet-eenthe efort arm and the ulcrum. &hese leversmultipl0 the orce but the direction sta0s the

    same.!xample1 -heelbarro-2 stapler2 bottle opener2nger nail clippers2 nut crac6er

    L2 effort arm > L1- load armMechanical advantage is more than one

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    SECOND CLASSLEVERS

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    THIRD CLASSLEVERS

    L2 effort arm < L1- load arm

    Mechanical advantage is less than one

    ot recommended in

    engineering practice

    7rd%lass Lever /&he efort orce is located bet-eenthe ulcrum and the resistance. &he efort arm isal-a0s shorter than the resistance arm so it cannotmultipl0 the orce and the #A is al-a0s less than .

    !xamples1 ra6e2 hoc6e0 stic62 broom2 shovel2 shing pole2t-ee8ers2 tongs

    .RD

    CLASS LEVERS *TWEE/ERS+

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    THIRD CLASSLEVERS

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    ANALYSIS TO SIMPLEMACHINE

    !he castings must be lifted 2"" mm

    FORCE ML!"#L"ER R$!"O %MEC&$'"C$L $()$'!$*E+

    #n the lever system shown in figure $ above% the load being lifted is about

    three times more than the effort being applied. !he load divided by the effort

    gives a ratio. !his ratio is a force multiplier% or how much more load can belifted compared to the effort.

    !he lever in figure therefore has a force-multiplier ratio of 2.&& (a ratio has no

    units of value'.

    . EFFORT = 260 N

    LOAD = 750 N

    600 mm

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    ANALYSIS TO SIMPLEMACHINE

    Example 1

    Find the force-multiplier ratio for the lever in figure above.

    Force-multiplier ratio load

    effort

    )*"

    2+"

    2.&&

    EFFORT = 260 N

    LOAD = 750 N

    600 mm

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    ANALYSIS TO SIMPLEMACHINE

    Find the distance-multiplier ratio leverage for the lever in figure $ above.

    ,ovement-multiplier ratio distance moved by the effort

    distance moved by the load

    +"" mm

    2"" mm

    EFFORT = 260 N

    LOAD = 750 N

    600 mm

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    ANALYSIS TO SIMPLEMACHINE

    Example

    Find the efficiency of the lever system shown in figure $.

    Efficiency (' Force /atio 1""

    ,ovement /atio

    2.&& 1"" 0+%

    !he system shown in figure has an efficiency of nearly 1"" per cent. o

    system can be 1"" per cent efficient there are always losses. !he losses in a

    lever system consist of energy lost to friction at the fulcrum of the lever andthe energy lost in strain as the lever bends slightly. #n some cases a small

    amount of energy will also be lost in the form of sound.

    Remem,er no machine is 1.. /er cent efficient0 Common

    energ losses include heat energ due to friction strainener and sound ener 0

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    DESIGN OFLEVERS

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    DESIGN OFLEVERS

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    DESIGN OFLEVERS

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    DESIGN OFLEVERS

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    DESIGN OFLEVERS

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    CROSS SECTION OF LEVERARM

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    CROSS SECTION OF LEVERARM

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    CROSS SECTION OF LEVERARM

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    E0AMPLE

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    E0AMPLE

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    E0AMPLE

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    E0AMPLE

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    TYPES OFLEVERS

    10 &$'( LE)ER

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    TYPES OFLEVERS

    20 FOO! LE)ER

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    TYPES OFLEVERS

    30 CR$'4E( LE)ER

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    TYPES OFLEVERS

    50LE)ER FOR $ LE)ER $FE!6 )$L)E

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    TYPES OFLEVERS

    70 8ELL CR$'4 LE)ER

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    O-1ECTIVE

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    O-1ECTIVE

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    O-1ECTIVE

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    O-1ECTIVE

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    O-1ECTIVE

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    O-1ECTIVE

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    O-1ECTIVE

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    O-1ECTIVE

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    THAN2 YO3