Assisted Bench Press Machine JARRED MORALES JUNKUN MA SPRING 2014 SOUTHEASTERN LOUISIANA UNIVERSITY

Negative Reps  Intensify workouts  Overload muscle groups  Control the tempo of the repetition for a 3-5 seconds rep count  25% more than you can lift  Eccentric phase causes muscle fiber damage

Assembly  Adjustable flat bench  45 pound barbell  two single acting cylinders  Front flange mount  U-bolts

Adjustable flat bench  Middle notch is the neutral position  The lower notch brings the bench closer to the floor  Accommodate for different arm lengths

Stroke Length  Laying forward grip reach  Drillis and Contini  Body segment lengths expressed as a fraction of body height H.  5’8’’(.438)=30in  Vary due to grip on the bar

Continuity Equation  Steady flow in a pipeline means weight flow rate is the same for all locations  Single inlet/outlet, no fluid added or withdrawn— Qi=Qe  Q=VA

Flow Characteristics

Volume Flow Rate  Required pump volume flow rate  Fluid volume swept out by the piston traveling through its stroke over a period of time  2in diameter

Schematic

Single Acting Cylinder  One port  Pressure from the fluid forces piston up  Force from weight pushes piston down

Pressure

hydraulic cylinder cushion  Prevents slamming from end to end  Plunger decelerates piston at the end of extension and retraction strokes  Creates a higher pressure

Cushion Equations

Directional Flow Control Valve  three way, two position, spring offset, pilot operated, directional control valve normally open

Pressure compensated flow control valve  The breaks  Maintain an essential constant flow rate with variations in inlet and load pressures  A spool is held by a set to set psi spring keeping it normally open

The type of pump  Requires a low pressure with a low volume flow rate  Ignoring OHP  Type of oil

Pressure Regulator  Connected between the pump and the DCV  Pressure changes due to variation in amount of weight being lifted  Can be adjusted to change amount of assistance

Check Valve  Between the pressure regulator and directional control valve  Prevents flow from flowing back to the regulator

Accumulator  Nitrogen filled bladder  Elastic barrier is between oil and gas  Safety mechanism  The volume decreasing in gas, causes an increase in stored energy

Reservoir  Storage space for excess fluid  Way of filtering  Metal chips, sludge, and water will be removed from oil  High enough oil level to prevent whirlpool effect  Surface area for heat dissipation and air space for thermal expansion

Conclusion/Future Design  Replaces need for assistance and most of the bench press assembly  Monitored the rate at which the cylinder descends, using a pressure compensated fcv  Applicable for different ranges of weight and people  Could have used a double acting cylinder with a four way, two direction control valve and eliminated the need of the weights

Thank you  Dr. Junkun Ma  Mr. James Stutts