1. Engineering Analysis & Updated Layout Drawings SofaKing 9 March 2005

2. Agenda Re-visiting Layout Drawings –Upright –Down –Locking Mechanism –Sliding Mechanism Engineering Analysis –Bolt Shear Stress –Beam Deflection –Spring

3. Upright Position

4. Down Position

5. Locking Mechanism

6. Sliding Mechanism

7. Engineering Analysis

8. Bolt Shear Stress Calc. Single Shear Equations Double Shear Equations SAE Grade 5 bolts – Bolt Shear Strength 120,000 psi

9. 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

10. Beam Deflection Loading Scenario Worst Case Scenario

11. Beam Deflection Calc. Moment of Inertia for Tubular Beam

12. Summary of Beam Deflection

13. 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.

14. Weight of Upper and Lower Frame Length of Tubing = 328 inches Density of Steel = 490 lbs / ft 3 Weight of Frame = 40.5 lbs

15. Loading of Upper Frame

16. 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. 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.)

17. Range for Spring Constant Converted: Minimum Spring Constant – 9.75 (lb-in/deg) Maximum Spring Constant – 12.0 (lb-in/deg)

18. Torsion Spring Parameters