SofaKing:The Lazy-Man Futon

Chris WooldridgeLoren HanklaAnkur DesaiJT Stukes

Barrett EvansJohn Pendley

Agenda

• Problem Statement

• Functional Requirements

• Design Partition

• Solution

• Engineering Analysis

• Prototype

• Conclusions

• Questions

Problem Statement

• Futons can be bulky and difficult to adjust

• Create a method to transform the futon with minimal user effort

• Mechanism must be cost efficient

• Must be able to endure normal everyday use by an adult

Functional Requirements

• Single hand operation (maximum of 20 lbs of force)• Reliable in terms of life expectancy of design• Safely move back and forth without fast moving parts• Futon should not hit wall or floor when converting• Minimize areas where fingers or clothing may get caught• No sharp corners or edges• “Lock” mechanisms to prevent accidental shifting• Aesthetically pleasing• Fairly lightweight

Design Partition• User Interface: The mechanism the user will

access to adjust the futon

• Sit-up Mechanism: This will transform the futon from the down position to the up position

• Lay-Down Mechanism: This will transform the futon from the up position to the down position

• Moving from Wall Mechanism: This will allow the user to open the futon without having to move the entire unit away from the wall

Solution: The Lazy-Man Futon

The Lazy-Man Futon

Locking Mechanism: Upright

Locking Mechanism: Down

Total System: Down

Engineering Analysis

Bolt Shear Stress Calc.

2/4)( dForcestressshear

Single Shear Equations

22 /604)83(/)6400(*4 inlbsinchboltslbs

Double Shear Equations

2/*2)( dForcestressshear

SAE Grade 5 bolts – Bolt Shear Strength 120,000 psi

Beam Deflection Calculations

• Frames will be made from 1 inch O.D. tubing. The thickness of each tube will be 0.3 inches

• Lower Frame will be designed to support two adult males. Each male is assumed to weigh less than 200 lbs.

• Maximum beam deflection shall be calculated and checked

Beam Deflection Calc.

22 4324

alEI

WaCenteratDeflection

alEI

WaLoadsatDeflection 43

6

2

236

avlvEI

WaLoadsBetweenDeflection

SteelAISIkpsiModulusElasticE 1030000,30)(

)(4

41

42 rrI

Moment of Inertia for Tubular Beam

Summary of Beam Deflection

Torsion Spring Design

• Torsion Spring should require no more than 20lbs to lower upper rail

• Mattress should not weigh more than 40 lbs. Similar mattress weighed 35 lbs.

• Weight of frame is calculated to be less than 30 lbs.

• Weight of Individuals shall be supported by the Locking Mechanism, not the torsion springs.

Weight of Upper and Lower Frame

inchesTubingofLengthTotal 368

TubingofLengthTotalLengthUnitPer

TubeofVolumeSteelofVolumeTotal *

SteelofDensitySteelofVolumeFrameOfWeight /

Length of Tubing = 328 inches

Density of Steel = 490 lbs / ft3

Weight of Frame = 40.5 lbs

22

122 )

44( in

dd

LengthUnitPer

TubeofVolume

Loading of Upper Frame

Torsion Spring Design

• Balance moments about pin connection to calculate necessary strength of spring

• Minimum spring strength necessary to prevent back from moving equals 0.8125 (lbs – in/deg).

DN

EdRt 2.10

4

3

2.10

d

MS

d = Wire size (inches) D = Mean diameter (inches) Torsion Spring.N = Number of active coils (front side) Rt = Rate of Torsion (Inch-lbs./Rev.)

S = Stress (lbs. /sq. inch)

M = Moment (Inch-lbs.)

P = Load (lbs.)

Range for Spring Constant

Converted:

Minimum Spring Constant – 9.75 (lb-in/deg)

Maximum Spring Constant – 12.0 (lb-in/deg)

Constructing the Prototype

The Lazy-Man Prototype

Spring: Upright and Down

Sliding Mechanism: Drawer Slides

Lazy-Man Futon VideosLinks:

Conclusions

• A viable design was for a futon that can easily be adjusted was created

• SofaKing feels that there is a place in the market for such a product

• Several additional considerations to the design should be made in terms of materials– Bolts appeared to be much stronger than needed– Metal tubing may be thicker than necessary– SofaKing feels that there is a place in the market for

such a product

Questions?