Safe Spot ME 4182 Final Presentation April 26 th, 2006 J.J. Couvillion - Elisha Mellitz - Manish Patel - Nick Roberts - Drew Bartlett

Objectives Problem Statement Project Selection/Design Goals Calculations and Design Adjustments Subsystem Overview Prototype Presentation Demonstration Video Conclusion

Problem Statement The bench press is an unsafe exercise when performed without a spot There is a need for a bench press system or apparatus which allows the user to safely spot themselves Apparatus must be safe, simple, reliable and durable

Project Selection A safe self-contained free weight bench with spotting capability Design Goals Must be compatible with standard Olympic weight sets Should allow freedom of motion in all directions Self contained system requiring no external power source

Engineering Analysis and Material Selection

Material Selection Steel is ideal choice for many reasons Existing elements are steel Desired mechanical properties –Obtained from Gere Mechanics of Materials 4 th Edition Easily obtainable ASTM standards

Catch Arm Calculations

Pivot Point/Bolt ¼” 1-1/2” 1/2” lb/in lb/in 13 2

Safety Factor: 1.85 Tension Wire Properties/Calculations TT

Kinematic Analysis The average person has at least 9” of motion in their legs when positioned on the bench press People in a wide height range will be able to press the required distance to get the weight back to the rack Locking device ensures that user will be able to safely evacuate in the event that user is unable to return bar to rack

Performance Analysis The force required by the leg press is 33% greater than the load from the weight. Using both arms and legs, the user should still easily provide enough force to lift the bar to safety. Lowest safety factor occurs in cable system (X=1.85) - still an acceptable level of safety.

Design Presentation

Safespot Weight Bench Design Weight bench follows Olympic standard measurements Addition of three main subsystems –Leg Press –Catch Arms –Cable and Pulley System

Previous Design Modification – Leg Press Previous design used a leg extension system Weaknesses –Doesn’t utilize complete strength of legs –Limited user height range –No locking mechanism

Updated Leg Press Assembly Leg press system used as the power source Utilizes strongest leg motion Locks the weight bar in a safe location

Catch Arms Swings up to secure bar safely above user Rotates about pivot point by cable connected to leg press Catches Cable pulls back of arm down Pivot Point

Cable System Transfers power from leg press system to catch arm assembly

Prototype Presentation

Prototyping Schedule

Wood Prototyping Initial wooden leg press assembly revealed necessary saw tooth design change Bracket placement and shape adjusted to avoid torsion of rods

Saw Tooth Design Modification Old Design – teeth angled upward Updated Design – leveled teeth profile

Prototype – Leg Press

Prototyping – Bench Frame

Prototype – Cable/Catch Arm

Prototype Presentation

Prototype Finances

Video Demonstration Movie Link (.mp4)Movie Link (.mp4) Movie Link (.avi)Movie Link (.avi)

Recommendations Adjust position of leg press to provide a more natural extension. Utilize higher quality cables that do not retain bends and kinks from curves. Adjustments for the aesthetics would be required for marketing this product. Lighter material and material reduction needed to aid in mobility of bench as well as allow quieter operation.

Conclusion A self-powered spotting weight bench is a feasible product –Catch arms are an effective method to lift and secure weight bar –Improved cable and pulley selection would allow easier operation and system durability Adjustments required to create a spotting bench with adequate support and marketability Questions?