Discover: Discover: Learning about: Gears & Worm Drives Learning about: Gears & Worm Drives What is a gear and how is it used? What is a gear box? Relation between force and speed How does the gear’s diameter affects speed Gear ratio What is gear ratio and how is it calculated? Have you ever thought how the huge and heavy cargos are and power? The gearbox concerns any combination or assembly of gears and loaded or removed from ships? Dockside cranes are responsible can be found in a variety of devices: from the smallest wrist for this process and are essential for every commerce port. In watch to the biggest train! In this experiment we will learn all this experiment you can build a similar type of dockside crane about this ingenious assembly, which allows us to control the Level Of Difficulty Level Of Difficulty model and learn more about gears and how they are used. speed of any machine. 1. Complete the following table according to your 1. Complete the following table according to your Materials Needed: Materials Needed: measurements and observations. Mark with ü the appropriate measurements and observations. After you take all - Engino® Simple Machines (STEM40) or Gears - Engino® Simple Machines (STEM40) or Gears boxes for FORCE and LIFTING SPEED. Results may vary but trend should measurements, complete the FORCE row with the word: easy, & Worm Drives (STEM05) or Master Set & Worm Drives (STEM05) or Master Set stay the same. medium, difficult and most difficult. Also, fill in the last row (STEM50). (STEM50). 1. 2. 3. 4. with a simplified ratio of input revolutions to output revolutions. CASES 1. 2. 3. 4. Procedure: Procedure: 1. Find the instructions in page 28 and build 1. The base of the gearbox will be step 4 of the experimental crane model. For case 1 the experimental crane in page 28. For case Crank’s revolutions 105 12 7 155 make the first gear assembly of page 29. 1 make the first assembly of page 31. easy CASES output output input input input 2. Position the experimental crane on a table FORCE medium 2. In the experiment we need to measure output output input (difficulty) and lower the load (weight) down to floor difficult how many revolutions the output shaft level. Then wrap and tie the string around the the most makes when the input crank rotates. Two axle, so it becomes tight. This should be the difficult people are needed for this: one should turn slow starting point for every case. the crank slowly with the appropriate INPUT 1 10 15 30 medium number of revolutions (as stated in the table) LIFTING 3. Turn the crank and measure how many SPEED and the other should measure the output fast OUTPUT 15 15 10 2 revolutions are needed until the load reaches revolutions. You can connect another crank the top (orange pulley). Write your answer in the fastest at the shaft of the output gear to help you the next table for case 1. Also, try to feel the measure the revolutions with more ease. FORCE most difficult difficult medium easy amount of force you have to apply in order to 2. Look at the “FORCE” row and the “LIFTING SPEED” row of the lift the load and observe the lifting speed. table and write your conclusions regarding the relationship 3. For case 1, revolve the input crank 1 time INPUT 1:15 2:3 3:2 15:1 OUTPUT between the force applied and the elevation speed of the load. (1 full circle). While measuring revolutions, 4. Repeat the same procedure for cases 2, 3 feel the amount of force you apply. 2. Why the gear ratio (input revolutions to output revolutions) is and 4, in which the gears are assembled as in The different gear assemblies require different amount of force in different in each case? What about Torque? pages 29 and 30. Try to keep the same order to lift the weight. The more force is needed (more difficult in 4. Repeat the same for the remaining cases. turning pace in each case. Write your findings For case 2, make the second gear assembly In cases 1 and 2, the output speed is increased and the Torque is in the table about the crank’s revolutions. terms of effort), the fastest is the lifting speed of the load and vice of page 31 and turn the crank 10 times. For decreased, as one gear drives a smaller one. In cases 3 and 4, speed versa. case 3 make the third assembly in page 32 5. Compare the amount of force you used in and turn the input crank 15 times. Finally, for is decreased and Torque is increased as one gear drives a larger one. each case ticking the words easy, medium, case 4 make the fourth assembly in page 32 difficult, the most difficult. Also, compare and turn the input crank 30 times. 3. Make the following calculations concerning the gear the lifting speed with the words slow, 3. Complete the conclusion below using the words in the box. assembly of case 1 and compare your result with the medium, fast and the fastest. Each word 5. Write down how difficult it is to turn the decrease, smaller, driver gear, driven gear, force, increase input/output ratio you found in the table above. What is the should be ticked once. crank for each case at the FORCE row, using connection between the number of teeth ratio and speed ratio? the words: easy, medium, difficult, and To increase speed, the .........................driver ................................ gear has to 6. Complete the conclusions in exercises 2 most difficult. In the last row divide the 6 teeth of small gear gear gear and 3. driven gear INPUT by the OUTPUT revolutions and write it gear pair 1 = = x be bigger than the ............................ ................................, while to pair 1 pair 2 as a simple ratio. Then, answer question 2. teeth of medium gear 18 .............................................decrease speed the driver gear has to be 6 6 6 1 teeth of small gear = x = bigger 6. Measure the number of teeth of each gear: gear pair 2 = = .............................................. than the driven gear. However, what 18 30 15 large, medium and small. Then, look carefully teeth of large gear 30 force at the gear assembly of case 1. There are two The ratio of the number of teeth (output gear teeth/input gear teeth) ® you gain in speed you lose in ................................. and vice versa. Engino experimental crane model pairs: 1) a medium gear connected with a is the same as the speed ratio (input speed/output speed). small one and 2) a big gear connected with a 19 small gear. Keep this in mind for exercise 3. 20 Discover: Discover: Learning about: Gears & Worm Drives Learning about: Gears & Worm Drives How can you change the plane and How can we transfer motion in a gear Carousel direction of rotation? Transfer of motion system? Many amusement parks have at least one carousel, either with Did you know that helicopters have two rotors? They have one wooden horses or swings. The carousel rotates with the help of big rotor which makes the helicopter fly and a small tail rotor, gears, while cam mechanisms move the horses up and down, which rotates in a different direction! The tail rotor is required to creating the illusion of galloping. Its seats hang from the rotating balance the helicopter otherwise it would just spin in the air! Now Level Of Difficulty Level Of Difficulty table, which rotates faster and faster, elevating people to the top. you can experiment with your own Engino helicopter. 1. On the following picture, identify the input and output of the 1. Which part of the helicopter rotates faster: the tail crank or Materials Needed: Materials Needed: model and write it down in the appropriate box. Show also with the main rotor? - Engino® Simple Machines (STEM40) or Gears - Engino® Simple Machines (STEM40) or Gears arrows the direction of each motion. The main rotor rotates faster than the tail crank. & Worm Drives (STEM05) or Master Set & Worm Drives (STEM05) or Master Set (STEM50). (STEM50). output 2. What happens if we rotate the main rotor manually? Procedure: Procedure: 1. Find the instructions in pages 33-35 and 1. Find the instructions in pages 36-38 and When the main rotor is rotated manually, the crank rotates as well input build the carousel model. build the helicopter model. Note that the meaning that the gear assembly works in both directions. teeth of the two gears should mesh tightly 2. Play a bit with your model in order to together in order to take accurate 3. Count the number of complete revolutions of the main rotor understand how it works. Turn the crank measurements. when the tail crank rotates 5 times and write it in the box (handle) slowly at first, then faster and below. observe what happens. 2. Turn the crank located on the tail of the helicopter and observe what happens. Then Revolutions of the main motor 15 3. Identify the input and output motion of rotate the main motor (the big blades) of the when the crank is turned 5 times your model and complete exercise 1. CRANK’S CAROUSEL’S helicopter with your hand and answer REVOLUTIONS REVOLUTIONS questions 1 and 2. 4. Compare your results with your answers in the previous 4. Now, compare the revolutions of the input 1 1 experiment of the carousel model. Are your results the same crank with those of the carousel (seats) and 3. Now turn the crank slowly for 5 times and this time? Why? complete the next table in exercise 2.