SofaKing: The Lazy-Man Futon Chris Wooldridge Loren Hankla Ankur Desai JT Stukes Barrett Evans John 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. Single Shear Equations Double Shear Equations ( shear stress ) 4 Force / d 2 ( shear stress ) 2 * Force / d 2 4 * (400lbs 6 bolts) / ( 3 8 inch) 2 604lbs / in 2 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. Deflection at Center Wa 24EI 3l 2 4a 2 Wa 2 Deflection at Loads 3l 4a 6 EI Deflection Between Loads Wa 6 EI 3vl v a 2 E ( Elastic Modulus) 30,000 kpsi AISI1030 Steel I (r24 r14 ) Moment of Inertia for Tubular Beam 4 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 Volume of Tube 2 d 2 d12 ( ) in 2 Per Unit Length 4 4 Total Length of Tubing 368 inches Volume of Tube Total Volume of Steel * Total Length of Tubing Per Unit Length Weight Of Frame Volume of Steel / Density of Steel Length of Tubing = 328 inches Density of Steel = 490 lbs / ft 3 Weight of Frame = 40.5 lbs 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). d = Wire size (inches) D = Mean diameter (inches) Torsion Spring. 4 Ed N = Number of active coils (front side) Rt Rt = Rate of Torsion (Inch-lbs./Rev.) 10 .2 DN S = Stress (lbs. /sq. inch) M = Moment (Inch-lbs.) 10.2M S P = Load (lbs.) d3 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 Videos Links: 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?
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