Advanced Design Applications Power and Energy © 2014 International Technology and Engineering Educators Association STEM  Center for Teaching and Learning™ Advanced Design Applications Teacher Resource Learning Cycle 3

Machine Components Mechanical Advantage © 2014 International Technology and Engineering Educators Association STEM  Center for Teaching and Learning™ Advanced Design Applications

What is Mechanical Advantage? What do you think it means? Let’s define each word separately: Mechanical Having to do with machinery Advantage A benefit, gain, or profit So what about mechanical advantage? A benefit or gain when using machinery © 2014 International Technology and Engineering Educators Association STEM  Center for Teaching and Learning™ Advanced Design Applications

What are the various components that we learned about? Threads Gears Bearings Springs Pulleys Clutches Brakes © 2014 International Technology and Engineering Educators Association STEM  Center for Teaching and Learning™ Advanced Design Applications

Which machine components will allow us to have mechanical advantage? Gears and Pulleys © 2014 International Technology and Engineering Educators Association STEM  Center for Teaching and Learning™ Advanced Design Applications

Gears What items can we change with gears? Number of teeth, speed, and torque Which of those items (when changed) can represent a mechanical advantage? TORQUE So if we have a gearset (two mating gears), how would we change the torque? Change the teeth! This is how we can calculate mechanical advantage! © 2014 International Technology and Engineering Educators Association STEM  Center for Teaching and Learning™ Advanced Design Applications

Gears – Mechanical Advantage This is how we determine mechanical advantage of gears: M.A. of Gears = Number of Teeth on driven gear Number of Teeth on driving gear © 2014 International Technology and Engineering Educators Association STEM  Center for Teaching and Learning™ Advanced Design Applications

Gears – Mechanical Advantage Example 1: You have a gear that has 15 teeth mating with a gear that has 47 teeth. The 15 tooth gear is the driving gear. MA = 47/15 = 3.13 This means that we have gained 3.13 times more torque than what we started with. © 2014 International Technology and Engineering Educators Association STEM  Center for Teaching and Learning™ Advanced Design Applications

Gears – Mechanical Advantage Example 2: You have a gear that has 17 teeth mating with a gear that has 51 teeth. The 51 tooth gear is the driver. MA = 17/51 = 0.33 What happened here? We went from a higher tooth gear to a lower tooth gear This decreased our mechanical advantage! NOTE: In order to increase mechanical advantage with gears, you must increase the number of teeth! © 2014 International Technology and Engineering Educators Association STEM  Center for Teaching and Learning™ Advanced Design Applications

Gears – Mechanical Advantage Practice Practice 1 – You have a driving gear of 11 teeth with a driven gear of 73. Practice 2 – You have a driven gear of 19 teeth with a driving gear of 7. Practice 3 – You have a driving gear of 55 with a driven gear of 13. © 2014 International Technology and Engineering Educators Association STEM  Center for Teaching and Learning™ Advanced Design Applications

Gears – Mechanical Advantage Practice Practice 1 – You have a driving gear of 11 teeth with a driven gear of 73. MA = 6.6 Practice 2 – You have a driven gear of 19 teeth with a driving gear of 7. MA = 2.7 Practice 3 – You have a driving gear of 55 with a driven gear of 13. MA = 0.24 © 2014 International Technology and Engineering Educators Association STEM  Center for Teaching and Learning™ Advanced Design Applications

Gears Continued What happens when you have a double or triple reduction? We have 2 gearsets for a double reduction We have 3 gearsets for a triple reduction What do you do? Find the mechanical advantage of each Then multiply them together! © 2014 International Technology and Engineering Educators Association STEM  Center for Teaching and Learning™ Advanced Design Applications

Gears – Multiple Reductions Practice – Reduction 1 has a driving gear with 13 teeth and a driven with 41. Reduction 2 has a driving gear with 17 teeth and a driven with 57. What is the overall mechanical advantage? Reduction 1 MA = 41/13 = 3.15 Reduction 2 MA = 57/17 = 3.35 Overall MA = 3.15 x 3.35 = © 2014 International Technology and Engineering Educators Association STEM  Center for Teaching and Learning™ Advanced Design Applications

Pulleys What are pulleys used for? To change the direction of a force To gain an advantage - (A mechanical advantage) © 2014 International Technology and Engineering Educators Association STEM  Center for Teaching and Learning™ Advanced Design Applications

Pulleys Mechanical Advantage This is how we determine the mechanical advantage of pulleys: Count the number of strings that are between moving pulleys! It is important to count only the number of strings between moving pulleys. If they do not move relative to one another, there is no mechanical advantage… This is also called a block and tackle system… © 2014 International Technology and Engineering Educators Association STEM  Center for Teaching and Learning™ Advanced Design Applications

Pulleys Mechanical Advantage Example The MA in this picture is 2! It is taking half as much force to lift the weight as it should. © 2014 International Technology and Engineering Educators Association STEM  Center for Teaching and Learning™ Advanced Design Applications

Pulleys Mechanical Advantage Practice © 2014 International Technology and Engineering Educators Association STEM  Center for Teaching and Learning™ Advanced Design Applications

Pulleys Mechanical Advantage Example Gun Tackle: 2 Luff Tackle: 3 Double Tackle: 4 Gyn Tackle: 5 Threefold purchase: 6 © 2014 International Technology and Engineering Educators Association STEM  Center for Teaching and Learning™ Advanced Design Applications

Multiple Component Systems What about systems that use gears and pulleys? There is a greater mechanical advantage! How is it calculated? Calculate the gear mechanical advantage Calculate the pulley mechanical advantage Multiply them together The product is the total mechanical advantage of the multiple component system © 2014 International Technology and Engineering Educators Association STEM  Center for Teaching and Learning™ Advanced Design Applications

What can affect your Mechanical Advantage? There are other things that can affect mechanical advantage… Friction (BAD!) Levers (GOOD or BAD) Complexity of device (BAD) Misalignment (BAD) Balance (GOOD or BAD) Materials (GOOD or BAD) © 2014 International Technology and Engineering Educators Association STEM  Center for Teaching and Learning™ Advanced Design Applications

Your Mechanical Advantage In the solar car project, you will try move a car with a given motor. You will be using gears to increase your mechanical advantage. You must be sure that your car is properly balanced, utilizes your material effectively, and decreases friction. What type of mechanical advantage will you have? © 2014 International Technology and Engineering Educators Association STEM  Center for Teaching and Learning™ Advanced Design Applications