Engineering Analysis Presentation ME 4182 Team: 5 Guys Engineering + 1 Nathan Bessette, Rahul...

Engineering Analysis Presentation

ME 4182Team: 5 Guys Engineering + 1

Nathan Bessette, Rahul Bhatia, Andrew Cass,

Zeeshan Saiyed, Glen Stewart

YJ Chok

Automatic Whiteboard Wiper

• 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

Calculations

Using the situation with the heavy writing

5”

2”

For 9.6 erasers to span the height of the board

For 4.8 erasers to span half the height of the board

Material AnalysisWeight Density [lb/ft3]

Mass Density

[slugs/ft3]

Yield Stress [ksi]

Ultimate Stress [ksi]

Modulus of

Elasticity E

[ksi]

Approximate Deflection

[in]

Aluminum 170 5.3 40 45 10000 0.0032

High Strength

Steel490 15.2 100 130 29000 0.0011

Stainless Steel

490 15.2 70 105 29000 0.0011

Polyethylene 75 2.35 N/A 2.5 150 0.2101

D L3 W

48 E I

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)

Eraser sub-assembly Weight Calculation

Eraser Subassembly Weight Calculation

• Density: ρ = 0.5097 lbs. / Ft. of bar• Quantity of bar

2 x 60” bars = 120”4 x 5” supports = 20”1 x (2” x 24”) eraser backing = 48”TOTAL = 15⅔ ft

• Aluminum Weight = 15⅔ ft · 0.5097 lbs. / Ft. ≈ 8 lbs.• Motor Assembly

Motor ≈ 2.3 lbRack & Pinion ≈ 1 lbExtras ≈ 0.5 lb

• Motor Assembly Weight ≈ 3.8 lbs.• TOTAL WEIGHT, W ≈ 11.8 lbs.

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, Nx 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

MB 0 (Ax 5 ft) (Nx 1.5 ft) (W 3.85

12ft)

Fx 0 Nx Ax Bx

Fy 0 Ay By W

Reaction Value (lbs)

Ax 2.03

Bx 3.47

Ay 2.95

By 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 (3.85 inches from

the wall, 1.90 feet from the bottom of the assembly)• Normal force from board, Nx 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

Reaction Value (lbs)

Ax 4.23

Bx 1.27

Ay 2.95

By 2.95

Fy 0 Ay By W

Fx 0 Nx Ax Bx

MB 0 (Ax 5 ft) (Nx 1.5 ft) (W 3.85

12ft)

Possible points of failure

Shear Analysis on the wheels

Wheels

Track

Top View

Front View Side View

Wheel SupportSupport Attachment

Area of the wheels under shear

Shear stress on the wheels due to weight

Area of one wheel under shear, Aw = 0.1266 in2

Total Area under shear, A T,w = 0.5063 in2

Shear stress due to Normal force, τN = Fs,W / A T,w = 5.825 psi

Shear strength of Nylatron, Sy = 10,500 psi

Factor of safety for the wheels, n = 1803


Fs,N = 2.950 lb


Fs,N = 4.229 lb

Shear stress on the wheels due to Normal Force

Area of one wheel under shear, As = 0.0765 in2

Total Area under shear, A T,s = 0.3061 in2

Shear stress due to Normal force, τN = Fs,N/ A T,s = 13.816 psi

Shear strength of Nylatron, Sy = 10,500 psi

Factor of safety for the wheels, n = 760

Horizontal Torque Requirements

• Required Torque calculation:

T = Fmax tension due to friction·rpulley

= (7 lbs.)(2.25 in.)

= 15.75 lb-in

= 1.3 lb-ft

Treq = 1.3 lb-ft minimumFmax, tension = 7 lbs.

Treq = 2.6 lb-ft

Motor

4.5” ID Pulley

Vertical Torque Requirements

• Required Torque calculation:

T = Fmax(friction+weight)·rgear

= (12 lbs.)(1.875 in.)

= 22.5 lb-in

= 1.875 lb-ft

Treq = 1.875 lb-ft minimum

Fweight = 5 lbs.

Ffriction = 7 lbs.

Fweight = Weight of Motor Assembly (3 lb est.) plus Eraser Backing (2 lb est.)

Motor3.75” ID Gear

SupplierMotor

Number Motor Name Description

Ref. Voltage

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

74550-0642

Power Wheels

Motor only 12 0.477 24000 2513 0.209 1100

CIM FR801-001 (Chiaphua, Atwood)

Keyed output shaft, ccw 12 1.81 5342 559 0.789 244

Fisher-Price

74550-0642

Power Wheels

Motor and gearbox 12 181 56.8 133 13.9 25.1 6.1

Globe 409A586 2WD/4WD transfer mtr.

Motor only 12 0.182 9390 983 0.0811 429

Taigene 16638628 Sliding (van) door

Worm Gearmotor 10.5 22.1 75 7.9 9.59 3.4


Planetary Gearmotor 12 117 9.59 80 8.4 4.79 3.7

Nippon-Denso

E6DF-14A365-BB

Window Lift Worm Gearmotor 12.6 6.79 92 9.6 2.95 4.1

Motor Analysis

Minimum Torque Requirements:

Horizontal Sliding = 1.3 lb-ft

Vertical Sliding = 1.875 lb-ft

SupplierMotor


Ref. Voltage

Gear Ratio


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

74550-0642

Power Wheels

Motor only 12 0.477 24000 2513 0.209 1100

CIM FR801-001 (Chiaphua, Atwood)

Keyed output shaft, ccw 12 1.81 5342 559 0.789 244

Fisher-Price

74550-0642

Power Wheels

Motor and gearbox 12 181 56.8 133 13.9 25.1 6.1


Motor only 12 0.182 9390 983 0.0811 429

Taigene 16638628 Sliding (van) door

Worm Gearmotor 10.5 22.1 75 7.9 9.59 3.4



Nippon-Denso

E6DF-14A365-BB

Window Lift Worm Gearmotor 12.6 6.79 92 9.6 2.95 4.1

Horizontal Sliding: speed, high torque

Vertical Sliding: small, light weight

Motor Analysis

Minimum Torque Requirements:

Horizontal Sliding = 1.3 lb-ft

Vertical Sliding = 1.875 lb-ft

BULKY COMPARED TO GLOBE MOTOR

FACTOR OF SAFETY TOO SMALL

MINIMUM TORQUE NOT MET



sec

in.7.13

rev1

in.5.4

rad2

rev1

sec

rad1.6

SupplierMotor


Ref. Voltage

Gear Ratio


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

74550-0642 Power Wheels Motor and gearbox 12 181 56.8 133 13.9 25.1 6.1



Motor Analysis

sec

in.9.6

rev1

in.75.3

rad2

rev1

sec

rad7.3

Free Speed Calculations:

Fisher-Price:

Globe:

Across the board

Up/down board

Can the cable subassembly overcome frictional forces without breaking?

Proposed materials: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 the friction force. Since there 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.

With the chosen motor (maximum torque of 34 N-m = 25.077 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.

lb 7

022

0

fm

fmm

x

FF

FFF

F

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

Engineering Analysis Presentation ME 4182 Team: 5 Guys Engineering + 1 Nathan Bessette, Rahul...

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