2. Laboratory 4: Hardware Analysis & Synthesis General Engineering Polytechnic University

3. OVERVIEW ü Objectives ü Review ü Reverse Engineering ü Forces ü Gears ü Gear Trains ü Materials for Lab ü Procedure ü Written Assignment ü Recitation Topics ü Closing

4. OBJECTIVES ü Review the concept of sketching ü Understand the concept of reverse engineering ü Learn about the importance of torque & gears ü Use your new knowledge to find out how a device works

5. REVIEW ü Orthographic vs. Isometric Views ü Sketching Rules

6. REVERSE ENGINEERING ü Begins with the intact product –Works through the design process in the opposite direction ü Used to understand: –How products are made by other companies –The quality of the product

7. FORCES Force = m * a Torque - French for twist - A twisting force = F * l l1l1 l2l2 F1F1 F2F2 m = mass (lbs. or kg.) a = acceleration (ft/s 2 or m/s 2 ) F = Force (lbs. or Newtons) l = Distance from force to point of rotation (ft. or m) = Torque (ft-lbs. or newton meters) If F 1 =F 2, but l 1 <l 2, the right side of the beam will tip down, due to unbalanced torque. Equilibrium: 1 = 2 F 1 *l 1 = F 2 * l 2

8. TORQUE OUTPUT OF GEARS ü Small force (F 1 ) used to lift large weight (F 2 ) ü Penalty for increased torque –small gear turns through larger angle than large gear F1F1 F2F2 R1R1 R2R2 –indicated in ratio of revolutions/second (gear speed) in equation: F 1 * R 1 = F 2 * R 2 ( 1 = 2 )

9. GEARS ü Used to increase/decrease torque or speed ü Torque and speed inversely proportional ü Velocity ratio equals inverse of gear ratio Output = the destination of the rotation (e.g. a wheel) Input = the source of the rotation (e.g. a motor) Velocity Ratio = Input Output Gear Ratio = Output Input

10. TYPES OF GEARS ü SPUR GEAR: gear wheel having radial teeth parallel to axle ü CROWN GEAR: gear wheel with teeth set in rim perpendicular to its plane crown gear

11. TYPES OF GEARS ü IDLER GEAR: gear between two other gears to transmit motion from one to other –Changes direction of rotation –No effect on ratios –ODD number of gears First & last gear rotate in same direction –EVEN number of gears First & last gear rotate in different direction idler gear

12. SIMPLE GEAR TRAIN 12 4 n1n1 n2n2 n3n3 1 2 2 3 1 3 Gears with the same size teeth, ratio equal to ratio of number of teeth (n) on each gear.

13. COMPOUND GEAR TRAIN 1 2 3 4 5 6 7 8 n1n1 n2n2 n5n5 n6n6 n3n3 n4n4 n7n7 n8n8 Angular velocities of all gears are equal to that of the shaft on which they are mounted

14. MATERIALS FOR LAB ü WAO II Robot –Model MV-961 –OWI Incorporated –2 Portions Mechanical / Electrical Computer ü Toolbox with 17 tools

15. PROCEDURE ü Examining the Robot –Inspect the intact robot –Record the appearance of the robot –Include sketches of the robot, complete with the outside dimensions –Hypothesize how the robot works (Try not to look at the bottom of the WAO II) Examining Disassembling Understanding Reassembling

16. PROCEDURE ü Disassembling the Robot –After you instructor signs your hypothesis & sketches, obtain a toolbox, complete with tools –Take apart the robot. Do NOT break it –Record what you see as you take the robot apart –Sketch the inside of the robot including the gear train. Be sure to label Examining Disassembling Understanding Reassembling

17. PROCEDURE ü Understanding the Robot –Describe the different components that make up the whole device –Record the functions of the individual major parts –Learn how the Power Gear Linkages allow: Rotation on the axis located in the center of the robot Turning (rotation outside the axis) Translation (movement in a straight line) –Determine the Gear Ratio for the train of gears that link the motor to the wheels Examining Disassembling Understanding Reassembling

18. PROCEDURE ü Reassembling the Robot –Reassemble the device to working order –Refer to the WAO II manual for assistance (disregard the sensor portion of the manual) –Return the assembled WAO II to the box and give it to you instructor –Record any further observations, including improvements to the robot and assembly instructions Examining Disassembling Understanding Reassembling

19. WRITTEN ASSIGNMENT ü Use the form report on Page 55 to complete the lab report (Be sure to type out your answers on a different piece of paper) ü Include original sketches with the instructors initials ü Remember to create a title page

20. RECITATION TOPICS ü Explain how the device works ü Discuss components of the WAO II and their functions ü How do the parts fit together? ü Discuss the overall construction of the device ü Discuss the assembly instructions for the WAO II. Are they clear? If so, explain what is clear. If not, what changes would you make to the assembly instructions? ü Discuss you findings for the gear ratio.

21. CLOSING ü Be sure to label your sketches ü Avoid breaking parts ü Keep track of the pieces