Engineering Analysis. Team: 5 Guys Engineering + 1 Nathan Bessette, Rahul Bhatia, Andrew Cass, Glen Stewart

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1 Engineering Analysis Presentation ME 4182 Team: 5 Guys Engineering + 1 Nathan Bessette, Rahul Bhatia, Andrew Cass, Zeeshan Saiyed, Glen Stewart YJ JChok

2 Automatic Whiteboard Wiper Last Time Last Time Layout Drawings Layout or assembly drawings How individual parts or subsystems fit together as a whole Encouraged to use computer modeling software Drawings for actual design, not prototype This Time Present a critical analysis of the design Determine the areas that are most likely to fail Potential engineering and/or manufacturing problems

3 Calculations Using the situation with the heavy writing 2 5 For 9.6 erasers to span the height of the board For erasers to span half the height of the board

4 Material Analysis Weight Mass Density Density [lb/ft 3 ] [slugs/ft 3 ] Yield Stress [ksi] Ultimate Stress [ksi] Modulus of Elasticity E [ksi] Approximate Deflection [in] Aluminum D = L3 W 48 E I High Strength Steel Stainless Steel Polyethylene N/A Deflection Analysis For Vertical Slider Bar -Assume Circular cross section -5 ft. long -Half the normal force from the board acts at the center of the rod (5.5 lbs)

5 Eraser sub-assembly Weight Calculation

6 Eraser Subassembly Weight Calculation Density: ρ = lbs. / Ft. of bar Quantity of bar 2 x 60 bars = 120 4x5 supports = 20 1 x (2 x 24 ) eraser backing = 48 TOTAL = 15⅔ ft Aluminum Weight = 15⅔ ft lbs. / Ft. 8 lbs. Motor Assembly Motor 2.3 lb Rack & Pinion 1 lb Extras 0.5 lb Motor Assembly Weight 38lbs 3.8 lbs. TOTAL WEIGHT, W 11.8 lbs.

75 feet from the bottom of the assembly) Normal force from board, N x is 11 lbs and acts at the center of the eraser (1.

7 Statics Analysis (Eraser at bottom) Forces on A and B are reactions on Sliding Assembly from sliding rails. Total of two sliding rails attached together Weight acts at the center of gravity (3.85 inches from the wall, 2.75 feet from the bottom of the assembly) Normal force from board, N x is 11 lbs and acts at the center of the eraser (1.5 feet from the bottom of the assembly) Reactions calculated by summing forces and summing moments about a fixed point F y = 0 = A y + B y W F x = 0 = N x A x B x M = 0 = (A 5 ft) (N 1.5 ft) (W 3.85 ft) B x x 12 Reaction Value (lbs) A x 2.03 B x A y 2.95 B y 2.95

Statics Analysis (Eraser at Top) Forces on A and B are reactions on Sliding Assembly from sliding rails. Total of two sliding rails attached together Weight acts at the center of gravity (3.

8 Statics Analysis (Eraser at Top) Forces on A and B are reactions on Sliding Assembly from sliding rails. Total of two sliding rails attached together Weight acts at the center of gravity (3.85 inches from the wall, 1.90 feet from the bottom of the assembly) Normal force from board, N x is 11 lbs and acts at the center of the eraser (3.5 feet from the bottom of the assembly) Reactions calculated by summing forces and summing moments about a fixed point F y = 0 = A y + B y W F x = 0 = N x A x B x M B = 0 = (A x 5 ft) (N x 1.5 ft) (W ft) Reaction Value (lbs) A x 4.23 B x A y 2.95 B y 2.95

9 Possible points of failure

10 Shear Analysis on the wheels Front View Side View Track Wheels Support Attachment Wheel Support Top View Area of the wheels under shear

11 Shear stress on the wheels due to weight Area of one wheel under shear, A w = in 2 Total Area under shear, A T,w = in 2 Shear stress due to Normal force, τ N = F s,w / A T,w = psi Shear strength of Nylatron, S y = 10,500 psi Factor of safety for the wheels, n = 1803 F s,n = lb Area of the wheels under shear

12 Shear stress on the wheels due to Normal Force Area of one wheel under shear, A s = in 2 Total Area under shear, A T,s = in 2 Shear stress due to Normal force, τ N = F s,n / A T,s = psi Shear strength of Nylatron, S y = 10,500 psi Factor of safety for the wheels, n = 760 F s,n = lb Area of the wheels under shear

13 Horizontal Torque Requirements 4.5 ID Pulley Motor T req = 26lb 2.6 lb ft Required Torque calculation: T = F max tension due to friction r pulley = (7 lbs.)(2.25 in.) = lb-in = 1.3 lb-ft F max, tension = 7 lbs. T req = 1.3 lb-ft minimum

14 Vertical Torque Requirements Required Torque calculation: 3.75 ID Gear F friction = 7 lbs. Motor T = F max(friction+weight) r gear = (12 lbs.)(1.875 in.) = 22.5 lb-in = lb-ft F weight = 5 lbs. F weight = Weight ofmotor Assembly (3 lb est.) plus Eraser Backing (2 lb est.) T req = lb-ft minimum

15 Motor Analysis Supplier Fisher- Price Motor Number Motor Name Description Power Wheels Motor only Ref. Volt age Gear Ratio Stall Torque (lb-ft) Free Speed (rpm) Free Speed (rad/s) Torque at Peak Power, 10.5 V Supply (lb-ft) Speed at Peak Power, 10.5 V Supply (rad/s) CIM FR (Chiaphua, Keyed output Atwood) shaft, ccw Fisher- Price Power Wheels Globe 409A586 2WD/4WD transfer mtr. Taigene Sliding (van) door Globe 409A587 2WD/4WD transfer mtr. Motor and gearbox Motor only Worm Gearmotor Planetary Gearmotor Nippon- E6DF- Window Lift Worm Denso 14A365-BB Gearmotor Minimum Torque Requirements: Horizontal Sliding = 1.3 lb-ft Vertical Sliding = lb-ft

16 Motor Analysis Supplier Fisher- Price Motor Number Motor Name Description Power Wheels Motor only Ref. Volt age Gear Ratio Stall Torque (lb-ft) Free Speed (rpm) Free Speed (rad/s) MINIMUM TORQUE NOT MET Torque at Peak Power, 10.5 V Supply (lb-ft) Speed at Peak Power, 10.5 V Supply (rad/s) CIM FR (Chiaphua, Keyed output Atwood) shaft, ccw MINIMUM 12 TORQUE NOT 5342 MET Fisher- Price Power Wheels Globe 409A586 2WD/4WD transfer mtr. Taigene Sliding (van) door Globe 409A587 2WD/4WD transfer mtr. Motor and gearbox Motor only MINIMUM TORQUE NOT MET Worm Gearmotor BULKY COMPARED TO GLOBE MOTOR Planetary Gearmotor Nippon- E6DF- Window Lift Worm Denso 14A365-BB Gearmotor FACTOR 12.6 OF SAFETY 6.79TOO 92SMALL Minimum Torque Requirements: Horizontal Sliding = 1.3 lb-ft Vertical Sliding = lb-ft Horizontal Sliding: speed, high torque Vertical Sliding: small, light weight

17 Motor Analysis Supplier Motor Number Motor Name Description Ref. Volt age Gear Ratio Stall Torque (lb-ft) Free Speed (rpm) Free Speed (rad/s) Torque at Peak Power, 10.5 V Supply (lb-ft) Speed at Peak Power, 10.5 V Supply (rad/s) Fisher- Price Power Wheels Motor and gearbox Globe 409A587 2WD/4WD transfer mtr. Planetary Gearmotor Free Speed Calculations: Across the board Fisher Price: 6.1rad sec 1rev π 4.5in. 2π rad 1rev = 13.7 in. sec Globe: 3.7 rad sec Up/down board 1rev π 3.75in. 2 π rad 1rev = in. 6.9 sec

18 Can the cable subassembly overcome frictional forces without breaking? Proposed materials: t i l Bicycle brake cable (steel) Rubberized Nylon cable Here, we will analyze the 5 mm cable with the lowest tensile strength to ensure a sufficiently high factor of safety for the stationary board. Weight considerations are largely ignored for this analysis as they not pertinent to the direction of motion. A distributed load of 7 lbf is applied against the direction of motion of the cable due to the board friction present. Thus the motor force must overcome e the friction force. Since there e are 2 pulleys (top and bottom) aiding the path of motion of the eraser, the stress on the cables is halved indicating that the cable tension in summation must overcome eraser assembly friction, pulley/bearing friction, and applied motor stress. F m F > x Fm > 0 2 F = 7 lb f With the chosen motor (maximum torque of 34 N-m = ft-lb.) at a distance of 2 ft, the cable has a F of S of at least 20 which is ample to ensure that the cable, even with the smallest tensile strength, will not stretch or deform and will definitely not snap. This means that cost can largely dictate the cable material that is chosen. + F 2 m F f > 0

19 Automatic Whiteboard Wiper Next Time Part Drawings Prepare a complete set of part drawings Must contain enough information so the part can be fabricated Drawings are for the actual design, not for the prototype

Conceptual Design Presenta2on. ME 4182 Team: Guys Engineering Nathan Besse*e, Rahul Bha/a, Andrew Cass, Zeeshan Saiyed, Glen Stewart YJ Chok

Conceptual Design Presenta2on. ME 4182 Team: Guys Engineering Nathan Besse*e, Rahul Bha/a, Andrew Cass, Zeeshan Saiyed, Glen Stewart YJ Chok Conceptual Design Presenta2on ME 4182 Team: 5 + 1 Guys Engineering Nathan Besse*e, Rahul Bha/a, Andrew Cass, Zeeshan Saiyed, Glen Stewart YJ Chok Automa/c White Board Wiper Last Time Presented Revisions