TOOTHED WHEEL PRESENTED BY THET AUNG SAN

WHAT IS A GEAR? GEARS ARE THE MECHANICAL PARTS WITH TEETH WHICH CONNECT WITH ANOTHER TOOTHED WHEEL (GEAR). GEARS ARE ALSO SOMETIME CALLED TOOTHED WHEEL (OR) COG WHEEL.

HISTORY OF GEAR ACCORDING TO ONE OF GREEK PHILOSOPHER ARISTOTLE’S WRITHING, GEARS WERE ALREADY IN USE IN 350 B.C. (ABOUT 2,300 YEARS AGO).

500 YEAR AGO VS PRESENT

TYPES OF GEARS SPUR GEAR

TYPES OF GEARS Helical GEAR

TYPES OF GEARS Advantages -Higher load capacity Disadvantages -Slightly poorer efficiency with this type of tooth system. BEVEL GEAR

TYPES OF GEARS WORM GEAR

DESIGN FOR GEARS

BACKLASH OF GEAR BACKLASH IS CLEARANCE BETWEEN MATING COMPONENTS, OR THE AMOUNT OF LOST MOTION DUE TO CLEARANCE OR SLACKNESS WHEN MOVEMENT IS REVERSED AND CONTACT IS RE-ESTABLISHED.

WHAT ARE GEARS USED FOR? INCREASE SPEED: IF YOU CONNECT TWO GEARS TOGETHER AND THE FIRST ONE HAS MORE TEETH THAN THE SECOND ONE, THE SECOND ONE HAS TO TURN ROUND MUCH FASTER TO KEEP UP. SO THIS ARRANGEMENT MEANS THE SECOND WHEEL TURNS FASTER THAN THE FIRST ONE BUT WITH LESS FORCE.

INCREASE FORCE: IF THE SECOND WHEEL IN A PAIR OF GEARS HAS MORE TEETH THAN THE FIRST, IT TURNS SLOWER THAN THE FIRST ONE BUT WITH MORE FORCE. WHAT ARE GEARS USED FOR?

CHANGE DIRECTION: WHEN TWO GEARS MESH TOGETHER, THE SECOND ONE ALWAYS TURNS IN THE OPPOSITE DIRECTION. SO IF THE FIRST ONE TURNS CLOCKWISE, THE SECOND ONE MUST TURN COUNTERCLOCKWISE WHAT ARE GEARS USED FOR?

ADVANTAGES OF GEARS BY USING GEAR TRAINS, LARGE VELOCITY RATIO CAN BE OBTAINED WITH MINIMUM SPACE. GEARS ARE MECHANICALLY STRONG, SO HIGHER LOADS CAN BE LIFTED. GEARS ARE USED FOR TRANSMISSION OF LARGE H.F. THEY ARE USED FOR TRANSMITTING MOTION OVER SMALL CENTER DISTANCE OF SHAFTS THEY ARE USED FOR LARGE REDUCTION IN SPEED AND FOR TRANSMISSION OF TORQUE. GEARS REQUIRE ONLY LUBRICATION, HENCE LESS MAINTENANCE IS REQUIRED. USING GEAR SYSTEMS, WE CAN TRANSMIT MOTION BETWEEN NON-PARALLEL INTERSECTING SHAFTS. THEY ARE USED FOR POSITIVE DRIVE, SO ITS VELOCITY RATIO REMAINS CONSTANT. THEY HAVE LONG LIFE, SO THE GEAR SYSTEM IS VERY COMPACT.

DISADVANTAGES OF GEARS THEY ARE NOT SUITABLE FOR LARGE VELOCITIES. THEY ARE NOT SUITABLE FOR TRANSMITTING MOTION OVER A LARGE DISTANCE. DUE TO THE ENGAGEMENT OF TOOTHED WHEEL OF GEARS, SOME PART OF MACHINE MAY GET PERMANENTLY DAMAGED IN CASE OF EXCESSIVE LOADING. THEY HAVE NO FLEXIBILITY. GEAR OPERATION IS NOISY.

GEAR RATIO GEAR RATIO IS A RATIO WHICH NUMBER OF TEETH (DRIVEN GEAR) DIVIDED BY NUMBER OF TEETH (DRIVE GEAR). GEAR RATIO IS USED TO CALCULATE REVOLUTION PER MINUTE (RPM).

GEAR TRAIN GEAR TRAINS ARE USED IN ALMOST ALL MACHINES WHICH ARE DEALING WITH THE MECHANICAL POWER. SOME OF THE PLACES WHERE GEAR TRAINS ARE USED ARE ENGINES, LATHES, CLOCKS, GEAR BOX AND DIFFERENTIAL OF AUTOMOBILES ETC.

TYPES OF GEAR TRAIN SIMPLE GEAR TRAIN COMPOUND GEAR TRAIN REVERTED GEAR TRAIN PLANETARY OR EPICYCLIC GEAR TRAIN

CONCLUSION GEAR IS A TOOTHED WHEEL. THEY CAN BE USE TO INCREASE SPEED TORQUE FOR MECHANICAL SOLUTION. BECAUSE OF GEAR BOX, WE CAN CONTROL SPEED OF CAR. THEREFORE, GEARS WILL BE USEFUL TECHNOLOGY FOR LONG CENTURY.