Gear Ratios What are gears ratios? Calculating SR of gear systems Lesson 34 - Gear Ratios Gear Ratios What are gears ratios? Calculating SR of gear systems

Gears Recap Big Idea If we use a gear to “reduce” the output speed of a system, we will end up “multiplying” the output force Visa Versa If we use a gear to “multiply” the output speed of a system, we will end up “reducing” the output force.

Gears Recap The DRIVER GEAR is the first gear in the system and is the gear that has the energy source coupled to it The DRIVER GEAR moves the system DRIVER GEAR Please draw a picture of a bike in your notes and label the “driver” and “follower” gears

Gears Recap The FOLLOWER GEAR is the second gear in the system and is the gear that receives the energy from the driving gear The FOLLOWER GEAR is moved in the system FOLLOWER GEAR

Reducing vs. Multiplying We base the terms… MULTIPLYING or REDUCING gear systems based on the NUMBER of REVOLUTIONS of the FOLLOWER GEAR

Textbook Reading We are going to do a quick individual reading from the Science Focus Textbook Please read the pages listed… while you are reading be sure to look for the formula that calculates the SPEED RATIO Pages 287 - 289

Speed Ratio = # of Driver Teeth . # of Follower Teeth Speed Ratio Formula Formula for Speed Ratio of a Gear System… Speed Ratio = # of Driver Teeth . # of Follower Teeth Remember though, the ratio must be reversed to indicate the number of revolutions each gear completes… the first number always represents the # of revolutions the Driver Gear completes

Calculating Ratios Calculating a Ratio Speed Ratio = # of Driver Teeth . # of Follower Teeth SR Fraction = _____ Gear Ratio ____ : ____ From your formula, you end up with a SR fraction… you must simplify this fraction. DO NOT DIVIDE!!! Top Number = the size of Driver Gear 1st # = Number of spins the driver gear makes 2nd # = Number of spins the Follower gear makes Bottom Number = the size of Follower Gear Between your fraction and ratio… the numbers switch

Example Question Calculate the Speed Ratio of the Gear System… Follower Gear Driver Gear

Example Answer Start with the Formula 1 spins to 2 SR = # of Driver Teeth # of Follower Teeth SR = 60 30 SR = 2 or we write it… 1 1 spins to 2 GR = 1 : 2 Is this a Multiplying or Reducing gear system?

Example Question Calculate the Speed Ratio of the Gear System… Driver Gear Follower Gear

Example Answer Start with the Formula 3 spins to 1 SR = # of Driver Teeth # of Follower Teeth SR = 25 75 SR = 1 or we write it… 3 3 spins to 1 GR = 3 : 1 Is this a Multiplying or Reducing gear system?

Example Question Calculate the Speed Ratio of the Gear System… Driver Gear Follower Gear

Example Answer Start with the Formula 4 spins to 1 SR = # of Driver Teeth # of Follower Teeth SR = 20 80 SR = 1 or we write it… 4 4 spins to 1 GR = 4 : 1 Is this a Multiplying or Reducing gear system?

Your Assignment!!! Due for Tomorrow You are being given a short worksheet that is deals with everything that we have been working on in terms of gears We will go over this worksheet in class tomorrow. BE SURE TO SHOW ALL OF YOUR WORK WHEN YOU ARE COMPLETING THE CALCULATIONS Ask for help if you need it