GEAR BOXES

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WELCOME
PROJECT ON
GEAR BOXES
RK DUVVU
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TRAINING NEED
People are the most important and expensive
resources in the industry. The difference between
gain and loss in an industry depends upon the
skill of its employees and the extent to which
such skill can be effectively applied. People are
able to change, grow and develop, while other
industrial resources are concrete. Growth and
development is best achieved through training.
The employee must be trained, tested and be
declared competent before he/she can accept the
responsibility of his/her post
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GEAR TRANSMISSION

• Gearing is a very vital form of transmission of
  mechanical power.
• Universally adopted for almost all machine
  mechanisms.
• Type of Gear Transmissions
• Spur Gear,
• Helical Gear,
• Herring bone Gear,
• Bevel Gear,
• Rack and pinion,
• Worm and worm wheel.

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SPUR GEAR

• Spur Gears in any transmission system are
  employed for changing the speed and the torque
  and are fixed on shafts either rigidly or with
  sliding traverse.

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HELICAL GEAR

• Helical Gears can be used for transmitting
  motion between parallel shafts as between
  perpendicular shafts. Helical gears used for
  transmission at an angle are called SPIRAL GEARS.

• Advantages of Helical Gears
• Noiseless motion even at higher speeds.
• Smooth transmission of small gears with fewer
  teeth, at large transmission ratio ( up to 151)
• These gears must be rigidly installed on the
  shaft. These gears result in an axial force in
  one direction depending upon the direction of
  rotation and are used for transmitting small
  power.

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HERRING-BONE GEAR

• HERRING-BONE Gears are pairs of Helical Gears.
  These gears are used for large power
  transmission.

• Advantages of Herring-bone Gears in addition to
  Helical Gears
• No Axial Force. It is balanced axially in both
  direction of rotation.
• Large power transmission can be done at impact
  loads having frequent starts (inching).
• These gears also must be rigidly installed on
  the shaft.

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BEVEL GEAR

• Bevel Gear transmission is employed for
  transmitting motion from one direction to the
  other at any angle. In general 90 transmission
  is used mostly.

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WORM WORM WHEEL

• Worm and worm wheel gives a large single stage
  speed reduction in perpendicular direction. Such
  transmission gives lower efficiency of
  transmission due to increased frictional losses.
  For a noiseless motion, worm 1 is usually made of
  medium carbon / alloy steel and the worm wheel 2
  of bronze (or in some cast iron).

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RACK PINION

• The rotary motion of pinion 1 (small gear) is
  transformed into linear motion of the rack 2. For
  transmitting large power worm worm rack
  transmission is employed.

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SPUR GEAR NUMENCLATURE
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SPUR GEAR NUMENCLATURE
Nomenclature Symbol Formulae
Module Diametral Pitch Pitch Number of teeth Pitch Circle Diameter Tooth height Addendum Dedendum Root circle diameter Outside diameter Distance between the axis of the two mating gears t 1 t2 Pressure angle m D.P. P t D h h h D1 Do A a mp/? D/t t/D ?/p 1/m P ?.m 3.14m t D/m D t.m h 2.2 m h m h 1.2 m D1 Do 4.4m Do m (t2) A (t1 t2) m/2 20(usually) or 14½
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Tooth Thickness Measurement

• Tooth Thickness Sx
• Tooth Depth Hx

Hx
sx
Module (m) 1 1.5 2 2.5 3 3.5 4 5 6 7 8 9 10
Hx 0.7485 m 0.75 1.12 1.5 1.87 2.24 2.62 2.99 3.74 4.49 5.24 5.98 6.73 7.48
Sx 1.387 m 1.39 2.08 2.77 3.47 4.16 4.85 5.56 6.94 8.32 9.71 11.1 12.48 13.87
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DEFECTS OF THE GEARS

• Wear of one, few or all the teeth.
• One or few teeth broken or twisted.
• Burrs on the bore or the key way.
• Burrs on the internal splines of the gear bore or
  the tooth surface.
• Crack or damage on the rim or the bore of the
  gear wheel.

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LIMITS OF WEAR FOR DISCARDING

• OPEN GEAR TRANSMISSION and the surface speed up
  to 2 meter / second The tooth thickness (Sx)
  reduces due to wear by (0.5m) mm, where m is the
  module, or about 33 of the original tooth
  thickness.
• CLOSED GEAR TRANSMISSION (GEAR BOXES) for surface
  speeds over 2 meter / sec. the tooth thickness
  (Sx) reduces due to wear by (0.3m) mm or about
  20 of the original tooth thickness.

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MESHING OF GEARS

• The spur and helical gears must be assembled in
  such a way that the axes of the meshing gears are
  parallel and the distance between their axes is
  correctly established.
• The correct meshing of the spur and helical gears
  is decided by applying blue paste on the teeth of
  the driving gear, giving it several rotations and
  seeing to the blue marks on the teeth faces of
  the meshing driven gear.

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(a) Correct meshing covering 70 80 tooth
surface contact. (b) Axis not parallel. (c)
Axis not parallel and distance between them is
too small. (d) Axis not parallel and distance
between them is excess. (e) Axis are parallel and
distance between them is excess. (f) Axis are
parallel and distance between them is too small.
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LUBRICATION

• Proper Lubrication with timely addition /
  replacement plays vital role in maintaining the
  gear boxes with efficiency and increasing its
  working life.
• Oil level should be checked in all the gear boxes
  oil indicators / dip sticks.
• Oil level should be in between the minimum and
  maximum limits of the dip stick (or indicator).
• Testing of the lubricating oils used to be
  carried out periodically. The following tests are
  to be done
• 1. Dirt contamination
• 2. Moisture
• 3. Volatile materials (Benzene, kerosene,
  spirit etc,)
• 4. Viscosity
• 5. Acidity
• 6. Alkalinity due to soda (Na2 Co3) etc.,

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THANK YOU