# Gears, Sprockets, and Pulleys

• These three power train ratios elements transfer energy though rotary motion
• Change the speed of rotation
• Change the direction of rotation
• Change the amount of torque available to do work
• If one gear is turning clockwise, the other one will turn counterclockwise
• When two gears touch each other, they change direction
• Problem:
• One motor gears, two axles, and the rotation of both of them both needs to be anti-clockwise
• Gears
• A gear train is a mechanism used for transmitting rotary motion and torque through interlocking teeth
• A gear train is made when two or more gears are meshed
• Driver gear causes motion
• Motion is transferred to the driver gear
• When a gear misses a tooth and it skips a gear, it is called XXXX?
• Gears
• Mating gears always turn in opposite directions
• An idler gear allows the driver and the driven gears to rotate in the same direction
• Mating gears always have the same size teeth (diametric teeth)
• The rpm of the larger gear is always slower than the rpm of the smaller gear
• Gears locked together on the same shaft will always turn in the same direction and at the same rpm
• Gear Ratios
• Variables to know:
• n = the number of teeth
• d = diameter
• w = angular velocity (speed)
• t = torque
• subscripts in and out are used to distinguish between gears
• Equations to know
• GR = Gear Ratio
• GR/1 = nout/nin = dout/din/win/wout=tout/tin
• What is the gear ratio between gear A and gear B?
• A has 120T and B has 12 T so it is .6/1
• The number of the gear ratios present in a system is one less than the number of gears present in that system
• Idler gears do not affect the gear ratios. Therefore, the gear ratio would be one because A has 20T and D has 20T
• Pulley and Belt Systems
• dout/din = win/wout = tout/tin
• d = diameter
• w is the angular velocity or speed
• t = torque
• they go in the same direction
• Choices are moment (beam producing a force), angular velocity (when turning), or regular velocity (velocity in a straight line) and torque force (ft-lbs or N)
• Sprocket and Chain Systems
• nout/nin = dout/din = win/wout = tout/tin
• n is the number of teeth
• d is diameter
• w is the angular velocity or speed
• t is torque