# 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