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MAE 442 Mechanical Engineering Department N.C. State University

PERFORMANCE SHOCKS. MAE 442 Mechanical Engineering Department N.C. State University. Adam Shifflett  Heath Spivey  Scott Tedrick. Shock Overview.

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MAE 442 Mechanical Engineering Department N.C. State University

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  1. PERFORMANCE SHOCKS MAE 442 Mechanical Engineering Department N.C. State University Adam Shifflett Heath Spivey Scott Tedrick

  2. Shock Overview • Shocks provide resistance by forcing incompressible hydraulic fluid through valves or a series of high quality valve washers in the piston as it moves up and down.

  3. Shock Types Monotube/1 Way Damper 3 Way Adjustable Damper 2 Way Adjustable Damper Offers most “tunability”, used for both low and fast shaft movements Used in NASCAR Nextel Cup and Goodies Dash Series Most versatile and cost effective Pictures from http://www.penskeshocks.co.uk/

  4. Why use Monotube Shocks? • Best for racing and off-road applications • Higher performance made to tighter tolerances • Less Variance • Dissipate heat faster • Allow a larger bore size to be used in the same space • More damping control      Pictures from http://www.penskeshocks.co.uk/

  5. Nitrogen Valve End Cap Reservoir Piston Shock Parts The end cap provides containment for the rest of the assembly and maintains the volume of nitrogen used to fine tune the shock. The valve allows increased pressure to be applied into the reservoir and thus applies higher pressure to the fluid on the other side of the piston increasing the flow resistance throughout the shock, increasing damping. Pictures from http://www.penskeshocks.co.uk/

  6. Shock Parts The damper body provides a housing for the other components of the damper as well as providing a containment vessel for the fluid pressure that provides damping. The head valve piston provides tunable resistance to fluid flow via interchangeable valve washers.

  7. Shock Parts • Valve Stacks • Damping characteristics determined by compression and rebound valve stacks, which are made to flex under the force of fluid flowing through piston ports then to return to original shape • Insert thicker shims to increase damping • Individual shim thicknesses range from 0.004” – 0.020” • Each piston face has a standard 1° dished surface • Preloads valve shims flat against piston face Pictures from Penske 7000 Series Tech Manual

  8. Rebound and Compression valve stacks Pictures from Penske 7000 Series Tech Manual

  9. Path of Fluid Travel • High speed rebound/compression • Enters through piston orifices • Travels through piston orifices • Exits around deflected washer valve stacks • Low speed rebound/compression • Enters through piston orifices • Travels through piston orifices • Exits through piston orifices and shaft bleed hole without deflecting washer valve stacks Pictures from Penske 7000 Series Tech Manual

  10. Poppet and jet assembly: • Interchangeable jets • Provides broad range of adjustment for bleed past piston on rebound • Utilizes spring-loaded poppet valve to check flow • Better seal against flow • Quicker response time in direction changes Picture from Penske 7000 Series Tech Manual

  11. The shaft provides a mount point for the various methods of resisting fluid flow and also accepts the various jet options. Open, compression, or rebound jet options can be installed by replacing the jet and associated hardware located near the valve stacks. Pictures from Penske 7000 Series Tech Manual

  12. This schematic displays a full compression and rebound cycle • Quadrant 1 - Beginning of compression stroke - fluid travels through low speed bleed bypass • Quadrant 2 - Continuation of compression stroke - Fluid travels through compression valve stack • Quadrant 3 - Beginning of rebound stroke - Fluid travels through low speed bleed bypass • Quadrant 4 - Continuation of rebound stroke - Fluid travels through rebound valve stack 1 2 3 4 Pictures from Penske 7000 Series Tech Manual

  13. Low speed shaft bleed bypass flow path: At slow speeds, fluid travels through the slow speed shaft bleed bypass and is controlled by the jet/poppet assembly. Through interchangeable jets, low speed damping is fully adjustable. Picture from Penske 7000 Series Tech Manual

  14. Eyelet Assembly • High Angularity Spherical Joint • Allows for wide range of motion encountered in racing and off-road applications • Allows for easy interchangeability • Bleeder Valve • Allows removal of air when filling with hydraulic oil • Prevents bubble formation • Prevents bounce • Quicker resistance

  15. Cost 7300 series shock from Roehrig Enders Suspension Inc. Cost: $790. Weight: 2.1 lbs http://www.resuspension.com/cart/product.php?productid=15185&cat=1&page=1

  16. Two Types of Racing Shock Tests Shock Dynamometer Used in all racing shops and in the team transporter for at track testing. Vehicle Dynamics Rig Most teams rent out dynamics rigs for days at a time. Used to test many car components at once. Shock Testing

  17. Measures Force vs. Shaft Speed What is a Shock Dyno? Pictures from http://www.roehrigengineering.com/

  18. Machine compresses and expands the damper at known speeds and measures the force produced. Electric Motor with a drive belt and pulleys spin a crank plate which is attached to the damper shaft. Works much like a piston and cylinder in an ICE. Bolt holes in Crank Plate allow for different stroke lengths. Different pulley diameters allow for different rotational speeds. The load cell measures the force generated by the damper. How a Shock Dyno Works Pictures from http://www.roehrigengineering.com/

  19. How a Shock Dyno Works Pictures from http://www.roehrigengineering.com/

  20. The damping force exerted on the compression stroke is known as the bump, while the damping force as the shock is expanding is known as the rebound. Most dampers give more force in rebound than compression. The damping forces are only recorded at maximum velocity which happens once during the compression stroke and once during expansion. How a Shock Dyno Works Pictures from http://www.roehrigengineering.com/

  21. To insure all 4 shocks on a car are responding in the same manner. To find problems before they find you, such as: Contaminated oil Bad seals Warn parts Allows you to see theeffects of external adjustments. Why do you need a Shock Dyno?

  22. Shocks influence tire grip Determine how the car feels to the driver Adjusting shocks allow for a faster racecar Documentation and tests conducted on each shock allows for similar track set-ups Why do you need a Shock Dyno? Pictures from http://www.roehrigengineering.com/

  23. Electro-Magnetic Actuator Plays back real time track data collected from the onboard data acquisition system. Fully computer controlled with damper analysis software. Up to 45hp Motor Output on a 220 Volt Power Supply. Price Tag - $68,000 Example Dynamometer Picture from http://www.roehrigengineering.com/

  24. Used for tuning vehicle suspensions Hydraulic actuators simulate: Road excitation Downforce Cornering Braking Loads Advantages: Operates in a controlled environment Cost considerably less than track testing Vehicle Dynamics Rig Pictures from http://www.roehrigengineering.com/

  25. Vehicle Dynamics Rig • Test Methods • Track simulation examines body responses and contact patch loads at the tires. • Static tests measure ride rates, roll rates, and friction • Comprised of 7 posts • 4 hydraulic actuators provide road excitation • 3 actuators mount to the car • Font, Middle, Back • Scale pad under car shows normal force Pictures from http://www.roehrigengineering.com/

  26. Overview of Adjustability • Low shaft speeds • Dish of piston surface • More dish = more preload = more low speed damping Pictures from Penske 7000 Series Tech Manual

  27. Overview of Adjustability • Bleed through jet • Less bleed = more low speed damping Pictures from Penske 7000 Series Tech Manual

  28. Overview of Adjustability • High Shaft Speeds • Thickness of shim stack • Thicker shims = more high speed damping Pictures from Penske 7000 Series Tech Manual

  29. http://www.penskeshocks.co.uk/cardamper/7300series.htm http://www.roehrigengineering.com/ http://www.autoresearchcenter.com/index.php?main=home http://www.pensketechnology.com/Main.htm http://www.penskeshocks.com/ http://www.accessconnect.com/how.htm http://membres.lycos.fr/binuxracing/brakes.html http://www.geocities.com/paulk5worker/shocks.html http://www.resuspension.com/cart/product.php?productid=15185&cat=1&page=1 References

  30. Special Thanks to: Brian Wilson N.C. State Alumni #2 Nextel Cup Team Engineer

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