Gears Transmit rotary motion and torque Gears have positive engagement friction drives, belts

Gear Types Spur Gear Rack and Pinion Gear Internal Gear Helical Gear

Gear Types Bevel Gear Herringbone Gear Miter Gear Worm Gear

Power Transmission

Gear Geometry Pitch Diameter Size of equivalent friction rollers Pitch circle Line of Centers Number of Teeth Must be an integer value

Gear Kinematics Velocity Ratio Gear Ratio Pitch Circles d2d2 22 d1d1 11

Gear trains are used to achieve high ratios with moderate size gears. Train Value (TV) TV = (VR) 1 (VR) 2 (VR) 3 … Gear Trains

Example The gear train shown is used with an input speed of 1200 rpm, cw. Determine the output velocity :  in  out N 1 =24 N 2 = 36 N 3 =20 N 4 = 40 N 5 =16 N 6 = 64  out =1200rpm*(24/36)*(20/40)*(16/64)=1200*(1/12)=100rpm But, since power is conserved, the output Torque is increased by a factor of 12

Questions 1.If you design a vehicle which you would like to drive at a slower rate, you are better off to use a gear train rather than simply reducing the power level to the motor. Why? 2.What happens if you increase the diameter of the driving wheels?

Center of Rotation R b ll 22 Wheel radius= r (1) r  2 = (R-b)  (velocity hub axle 2) (2) r  l = (R+b)  (velocity hub axle 1) Angular velocity  Dividing (1) by (2)  2 /  l = (R-b) / (R+b) Solving for R R = b(  1 +  2 ) / (  1 -  2 ) A Three- Wheeled Vehicle with a Free Front Wheel Rear wheels differentially powered. r Note:  1 =  2 R =   1 =  R =  b  2 =  R =  b  1 =  2 R=0