LEAF SPRING

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LEAF SPRING
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Introduction

• A leaf spring is a simple type of suspension
  spring commonly used in heavy duty vehicles.
• The advantages of leaf spring over helical spring
  is that the ends of the spring be guided along a
  definite path as it deflects to act as a
  structural member in addition to energy absorbing
  device.

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Types

• Double eye
• Slipper-open eye end
• Slipper-hook end
• Slipper-flat end
• Slipper-radius end

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Construction of leaf spring

• Leaf springs used in automobiles is of
  Semi-Elliptical in form.
• It is built up of number of plates(known as leaf)
  , which are of reducing lengths.
• The longest leaf is called main leaf or Master
  leaf, And the other leaves are called as
  graduated leaves.
• The spring is clamped to the axle by means of
  U-bolts.
• Rebound clips are used to hold the leaves
  together.
• Central clamp is used to fix the position of leaf
  spring to the wheel axle.

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Construction of leaf spring
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Parts of leaf springs
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Manufacturing process

• The different types of manufacturing process
  involved are
• Shearing of flat bar
• Center punching
• End Heating process forming (hot cold process)
• Heat treatment
• Surface preparation
• Eye bush preparation process
• Assembly

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Standard sizes of leaf spring

• Width (mm) 25-80 mm in steps of 5mm
• Thickness (mm) 2-8 mm in steps of 1mm, 10-16 mm
  in steps of 2mm

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Material Used for Leaf Spring

• The materials used for leaf springs is usually a
  plain carbon steel having 0.90 to 1.0 carbon.
• According to Indian Standards the Recommended
  Materials are
• For Automobiles 50 Cr 1 , 50 Cr 1 V 23
  , 55 Si 2 Mn 90 , used in
  Hardened and Tempered state.
• For Rail Road Springs C
  55(water-Hardened , C 75-Oil hardened) , 40
  SI 2 Mn 90 (Water Hardened) and 55 Si 2 Mn 90
  (Oil hardened)

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Leaf Spring Design

• Bending Stress in each plate of the leaf spring
• B 6WL/(nbt 2)
• Deflection of the plate
• d4WL 3/(nEbt 3)

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Composite carbon fibre leaf spring

• Now-a-days industries are trying to reduce
  the weight and increase the strength of leaf
  spring for efficient suspension.
• ARC Composite carbon fiber is the best
  material suitable for the above required
  criteria.
• This material has less weight and high
  strength when compared to the materials using in
  the leaf springs using in nowadays leaf springs.

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Advantages of ARC Composite carbon fibre leaf
spring suspension

• 1) Specifically made to give effects like Air
  Suspension with out any extra external
  energy(Fuel)2) No permanent deformation hence
  no re-cambering, thus no maintenance.3) Minimum
  wear and tear of body parts and tyre due to
  delicate tendency of absorbing road shocks, jerks
  and vibrations.4) Softer ride, Lower noise
  level, excellent stability due to better damping
  characteristics.5) Excellent corrosion
  resistance against atmospheric pollutants.6)
  Five times stronger than conventional metal leaf
  springs.

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• 7) Fully interchangeable with the
  conventional spring without any
  modifications.8)Increase in fuel efficiency due
  to better aerodynamics and around 60 weight
  reduction.9) No cracking sound since mono leaf
  and hence no inter-leaf friction and no greasing
  required.10) Fatigue life 1 million cycles as
  compared to only 2 lacks for the metal leaf
  springs.

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