Gears

• There are four kinds of motion: Rotary, Linear, Reciprocating, Oscillating.
• Rotary motion is circular
• Linear motion is a straight line in one direction
• Reciprocating motion is a back and forth movement
• Oscillating motion is moving back and forth in an arc
• A gear is a toothed wheel used to transmit rotary motion and power from one part of a mechanism to another
• The ratio of change in speed between the gears is called the velocity ratio.
• Velocity Ratio = driven / driver
• Velocity Ratio = input speed / output speed
• An idler gear is used to change the direction of motion
• input speed x input size = output speed x output size
• Compound gears are required to produce a very large change in speed
• Torque is the amount of turning produced by a force
• Torque = Force x Radius
• You can use a belt drive to transfer rotary motion over relatively large distances
• Optimal belt drive:

  
• One of the advantages of belt drives is that they will absorb shock loads by slipping. However, excessive slipping will create inefficiency in the system.
• Where large forces have to be transmitted, and there can be no slippage allowed, chain drives are used.
• A cam is a specially shaped piece of metal or plastic which can be used to change an input rotary motion to an output motion that is oscillating or reciprocating.
• A rack-and-pinion mechanism is used to transform rotary motion into linear motion, or linear into rotary motion.