GEAR &GEAR TRAINS See the background of slide....!!! For pre-info about journey we are about to begin…….
LETS START WITH OURJOURNEY…. INTRODUCTION TO END GEARS AND GEAR TRAINS START APPLICATIONS TYPES OF GEARS GEAR TRAINS MANUFACTURING
WHAT ARE GEARS???• A friction wheel with teeth cut on it, i.e. ; a synchronous arrangement of projections and recesses on a wheel. projections recess
And Gear Trains??? Friction Wheels When two or more gears are mesh together to transmit power from one shaft to another; then such combination is called Gear Trains train of tooth wheels or gear trains.
+ and – ‘s of GEAR TRAINS Over belts , ropes and chain drives.+ Transmits exact VELOCITY RATIO* Compact layout and higher EFFICIENCY._ Making of Gears require special tools and equipments. Noise and vibrations are produced during their usage. * This is the true principle of gearing
Velocity RatioRatio of the distance moved by the EFFORT POINT and LOAD POINT. 2 N 2 d1 RATIO 1 N1 d 2
VARIOUS TYPES OF GEARS BASISPOSITION OF • PARALLEL • INTERSECTING AXES OF • NON-INTERSECTING AND NON- SHAFTS PARRALELPERIPHERAL • LOW VELOCITY. • MEDIUM VELOCITY.VELOCITY OF • HIGH VELOCITY. GEARS • EXTERNAL GEARING. TYPE OF • INTERNAL GEARING GEARING • RACK AND PINION.
PERIPHERAL VELOCITY OF GEARS• VELOCITY LESS THAN 3m/s : LOW • VELOCITY b/w 3m/s AND 5m/s:MEDIUM • VELOCITY GREATER THAN 15m/s:HIGH
TYPES OF GEARINGExternal Gearing Internal Gearing Rack and Pinion
MANUFACTURING MATERIALS FOR GEARSTYPE OF MATERIAL USED DEPENDS ON:• STRENGTH• SERVICE CONDITIONS LIKE NOISE,WEAR,etc.GEARS ARE MANUFACTURED BY:(commercially available)• METALLIC: CAST IRON,BRONZE AND STEEL.• NON-METALLIC: WOOD,SYNTHETIC RESINS like NYLON, especially used to reduce NOISE.
METALLIC GEARS arebasically used for rough mechanical purposes METAL SPECIFICATIONS USED CAST IRON GOOD WEARING (employed PROPERTIES,EXCELLENT where smooth MACHINABILITY AND EASE action is not OF PRODUCING COMPLEX that SHAPES USING CASTING important ) PROCESSES. steel Used where high strength gears are required and usually heat treated to provide toughness and tooth strength. Phosphor Used in worm gears to bronze reduce wear which will be max. with cast iron.
MORE ON MANUFACTURINGSOME TERMS ARE REQUIRED TO BE CONSIDERED WHEN WEDESIGN GEARS such as:MODULE: THIS IS THE RATIO OF PITCH CIRCLE DIAMETER (inmm) TO THE NO. OF TEETHm=(pitch circle diameter(in mm))/(No. of teeth)=D/T.RECOMMENDED SERIES OF MODULES IN INDIAN STANDARDSARE 0.5,1,1.5,2,2.5,3,4,5,6,8,10,12,16,20.CIRCULAR PITCH: IT IS THE DISTANCE BETWEEN A POINT ONONE TOOTH TO THE CORRESPONDING POINT ON NEXT TOOTH.PITCH= ∏D/T. REMEMBER: A LITTLE CONSIDERATION SHOWS THAT FOR GEARS TO MESH PROPERLY,IT IS NECESSARY THAT THEIR CIRCULAR PITCH IS SAME.
Resuming sree’s talk on GEAR TRAINS• A gear train is two or more gear working together by meshing their teeth and turning each other in a system to generate power and speed• It reduces speed and increases torque• Electric motors are used with the gear systems to reduce the speed and increase the torque
Types of Gear Trains• Simple gear train• Compound gear train• Planetary gear trainSimple Gear Train• The most common of the gear train is the gear pair connecting parallel shafts. The teeth of this type can be spur, helical or herringbone.• Only one gear may rotate about a single axis
Planetary Gear Train…• In this train, the blue gear has six times the diameter of the yellow gear• The size of the red gear is not important because it is just there to reverse the direction of rotation• In this gear system, the yellow gear (the sun) engages all three red gears (the planets) simultaneously• All three are attached to a plate (the planet carrier), and they engage the inside of the blue gear (the ring) instead of the outside.
Planetary Gear Train…• Because there are three red gears instead of one, this gear train is extremely rugged.• Planetary gear sets can produce different gear ratios depending on which gear you use as the input, which gear you use as the output, and which one you hold still.
Planetary Gear Train…• They have higher gear ratios.• They are popular for automatic transmissions in automobiles.• They are also used in bicycles for controlling power of pedaling automatically or manually.• They are also used for power train between internal combustion engine and an electric motor
APPLICATIONS DIFFERENTIAL DRIVER: A MIRACULOUS MECHANISM STARTING FROM A BASIC ASSEMBLY USING GEAR TRAINSA vehicles wheels rotate at different speeds,especially when turning corners. The differential isdesigned to drive a pairof wheels with equal force, while allowing them torotate at different speeds
Input torque is applied to the ring gear (blue), which turns the entire carrier (blue), providingtorque to both side gears (red and yellow), whichin turn may drive the left and right wheels. If the resistance at both wheels is equal, the planet gear (green) does not rotate, and both wheels turn at the same rate.
If the left side gear (red) encounters resistance, the planet gear (green) rotates about the left side gear, in turn applying extra rotation to the right side gear (yellow).
BIBLIOGRAPHY• “THEORY OF MACHINES” by PROF. KHURMI,R.S.• ARTICLES FROM WIKIPEDIA:”GEARS”.CITED ON 5/4/2011.• “THEORY OF MACHINES”,by SHINGLEY,JOSEPH EDWARD;JOHN UICKER.