STUDY OF MOTION AND POWER TANSMISSION ELEMENTS - BY SIMRANJEET BHATIA -130120119017 -SR NO.:24.
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Transcript of STUDY OF MOTION AND POWER TANSMISSION ELEMENTS - BY SIMRANJEET BHATIA -130120119017 -SR NO.:24.
GEAR TERMINOLOGY
PITCH DIAMETER
ROOT DIAMETER
CENTER DISTANCE
OUTSIDE DIAMETER
DIAMETRAL PITCH= TOOTH SIZE
CHAIN CHAIN
DRIVEDRIVE
Easier to remove/replace than beltsCompactSomewhat flexibleRelatively inexpensiveCan handle heat, dirt, weather exposure (when
properly lubricated)
GEAR GEAR DRIVEDRIVE
Gears are most often used in transmissions to convert an electric Gears are most often used in transmissions to convert an electric motor’s high speed and low torque to a shaft’s requirements for low motor’s high speed and low torque to a shaft’s requirements for low speed high torque:speed high torque:
Gears essentially allow positive engagement between teeth so high Gears essentially allow positive engagement between teeth so high forces can be transmitted while still undergoing essentially rolling forces can be transmitted while still undergoing essentially rolling contactcontact
Basic Law of Gearing:Basic Law of Gearing:
––A common normal (the line of action) to the tooth profiles at A common normal (the line of action) to the tooth profiles at their point of contact must, in all positions of the contacting their point of contact must, in all positions of the contacting teeth, pass through a fixed point on the line-of-centers teeth, pass through a fixed point on the line-of-centers called the pitch pointcalled the pitch point
––Any two curves or profiles engaging each other and satisfying Any two curves or profiles engaging each other and satisfying the law of gearing are conjugate curves, and the relative the law of gearing are conjugate curves, and the relative rotation speed of the gears will be constantrotation speed of the gears will be constant
SPUR GEARSPUR GEAR BEVEL GEARBEVEL GEAR
Teeth are parallel to the Teeth are parallel to the axis of the gearaxis of the gear
AdvantagesAdvantages– CostCost
– Ease of manufactureEase of manufacture
– AvailabilityAvailability
DisadvantagesDisadvantages– Only works with mating Only works with mating
geargear
– Axis of gear is parallelAxis of gear is parallel
Gear axis at 90°, based Gear axis at 90°, based on rolling coneson rolling cones
AdvantagesAdvantages– Right angle drivesRight angle drives
DisadvantagesDisadvantages– Get axial loading which Get axial loading which
complicates bearings complicates bearings and housingsand housings
WORM GEAR RACK AND PINION
• Gears that are 90° to each other
• Advantages– Quiet / smooth drive
– Can transmit torque at right angles
– No back driving
• Disadvantage– Most inefficient due to excessive
friction (sliding)
– Needs maintenance
• The rack and pinion gear is used to convert between rotary and linear motion.
– Could have straight or bevel teeth
– Provides less backlash
– Greater feedback
HELICAL GEARSHELICAL GEARS
Teeth are at an angle to the gear axis (usually Teeth are at an angle to the gear axis (usually 10° to 45°) – called helix angle10° to 45°) – called helix angle
AdvantagesAdvantages• Smooth and quiet due to gradual tooth Smooth and quiet due to gradual tooth
engagements (spur gears whine at high speed due engagements (spur gears whine at high speed due to impact). Helical gears good up to speeds in to impact). Helical gears good up to speeds in excess of 5,000 ft/minexcess of 5,000 ft/min
• More tooth engagement allows for greater power More tooth engagement allows for greater power transmission for given gear size.transmission for given gear size.
DisadvantageDisadvantage• More expensiveMore expensive• Resulting axial thrust componentResulting axial thrust component