The Great Team 1

Week 8 : Engineering Analysis

Bunk Bed Converter

Adam Brown

Blaine Gardner

Sarah Gleaton

Jimmy Jiang

Addisu Lemlem

Lee Tschaepe

7/12/2006

The Great Team 2

Locking Mechanism

The Great Team 3

Locking Mechanism

The Great Team 4

Pin Analysis

The Great Team 5

Bed PositionsUp Position- 0 degrees

rotation

Down Position- 90 degrees rotation

The Great Team 6

Free Body Diagram

Force from mattress and mattress frame

Force due to weight of arm

Torque to be generated by spring

*Maximum Torque is required in the vertical position

The Great Team 7

Pivot Arm

• Arm is 2” x 2” mild steel square tubing

• Each arm is 41” long

• Each arm weighs 10.905 lbs

• Torque generated @ 90 by each arm=

T= F(lbs) x L/2(in) => 10.905 x 41/2=

223.45 lb-in

The Great Team 8

Frame and Mattress

• Frame weighs 25 lbs

• Mattress weighs 50 lbs

• This force is distributed over 4 arms; each arm must support ¼ of this force.

The Great Team 9

Calculations

-Torque due to mattress and frame: (50/4)*41+(25/4)*41=768.755

-Torque due to weight of Pivot Arm:10.905*(41/2)=223.45 lb-in

Total Torque generated for one arm:992.25lb-in

The Great Team 10

Results

• If a torque of 850 lb-in is applied using a torsion spring, the user must lift 3.47 lbs per arm

• Total user required force to upper bunk assembly is 13.88 lbs

The Great Team 11

Bed Frame Analysis

Bed Frame Analysis

33

3

1acbabcbbacI

433 1845.0125.085.025.1125.025.185.025.125.185.025.03

1inxI

Secondary Moment of Inertia

c = center of mass = 0.85 in

Frame Analysis – Long Side Bending Stress

Long Side of Bed Frame

I

cMbending

max

Maximum Bending Stress

inlbinlbxFlM 8.64185.395.162max

kpsiin

ininlbxbending 6.29

1845.0

85.08.64184

Material: Carbon Steel 1040 CR, Yield Strength = 71kpsi

4.26.29

71

kpsi

kpsiSN y

Frame Analysis – Short Side Bending Stress

Short Side of Bed Frame

I

cMbending

max

Maximum Bending Stress

inlbinlbxFlM 3170205.158max

kpsiin

ininlbxbending 3.14

1845.0

85.031704

Material: Carbon Steel 1040 CR, Yield Strength = 71kpsi

0.53.14

71

kpsi

kpsiSN y

Frame Analysis – Bearing Stress

LONG SIDE SHORT SIDE

kpsiininx

lb

Dl

R

A

F ybearing

0.525.025.0

5.3124

max

kpsiininx

lb

Dl

R

A

F ybearing

5.225.025.0

1554

max

Bolt: D = 1/4”, Carbon Steel 1010 CR, Yield Strength = 44 kpsi

8.80.5

44

kpsi

kpsiSN y

6.17

5.2

44

kpsi

kpsiSN y

Frame Analysis – Shear Stress

LONG SIDE SHORT SIDE

kpsiininx

lb

Dl

R

A

F y

4.625.025.0

414.3

5.3124

max

kpsiininx

lb

Dl

R

A

F y

2.325.025.0

414.3

1554

max

Bolt: D = 1/4”, Carbon Steel 1010 CR, Yield Strength = 44 kpsi

9.64.6

44

kpsi

kpsiSN y

8.13

2.3

44

kpsi

kpsiSN y