DRAFT Amusement Rides: How much thrill is too much? Robert S. Cargill II, PhD, PE rcargill@jpresearch.com JP Research, Inc. Fort Washington, PA 215-486-6847
DRAFT Biomechanics of Amusement Rides • Standards and Amusement Rides and Devices • ASTM International committee F24 and F2291 • Biodynamics/Biomechanics • Basis for limits/guidelines • Quiz
DRAFT What do biomechanical engineers do?
DRAFT Standards-setting Bodies for Amusement Rides • EN (EuroNorm) • ASTM International • ISO (International Organization for Standardization) • Standards Australia • China
DRAFT ASTM International • Committee F24 on Amusement Rides and Devices — Jurisdiction over 19 standards — Committee scope covers test, design, operation, and maintenance — Standards cover a very wide range of types of rides — Traditional, water slides, ziplines, inflatables, Zorbs, trampolines, etc. • F2291 Standard Practice for Design of Amusement Rides and Devices — Covers all aspects of design of amusement rides and devices — Focus of this talk are the biomechanical requirements — In the form of acceleration limits
DRAFT ASTM F2291 History • Engineers, biomedical engineers, doctors, regulators, operators assembled in 2000-2001 to give recommendations to ASTM for acceleration limits. • First USA consensus acceleration limits standard approved 2001 Slides from ASTM F-24
DRAFT The Human Body • We must understand what people can endure — Where does the data come from? — Primarily, the military Ejection seats, aircraft pilots, armor, blasts, etc — Automobiles, sports, etc
DRAFT Human Tolerance • Human tolerance depends on: — Direction — +X, -X, +Z, -Z, Y — Y-axis direction not very important — Duration — Rate of application — Failure mechanism — Different parts fail for different reasons at different points — Global tolerance changes based on many factors
DRAFT What is the measure? • Many years of establishing biodynamic limits — Air Force – forward deceleration (Colonel Stapp)
DRAFT What is the measure? • Many years of establishing biodynamic limits — NASA, Air Force – acceleration “through the seat”
DRAFT What is the measure? • Many years of establishing biodynamic limits — Automotive, general examples — Head/brain injury: HIC (head injury criterion) — Calculated from the acceleration waveform — Chest injury: combination of acceleration and velocity — Called the viscous criterion — Work based on military and NASA work and included cadaver (post- mortem human subjects) testing — Forms the basis of the Federal Motor Vehicle Safety Standards
DRAFT Acceleration is the Measure • Standard biomechanical technique to normalize force to body mass Acceleration! • Tolerable limits depend on — Duration — Direction (for whole body)
DRAFT Acceleration • Acceleration – what is it good for? — F = m*a — Force directly affects your body — Your mass is (normally) constant — So acceleration is proportional to force — This is why we have acceleration standards and not height or velocity standards — So what changes? — Duration, direction, location
DRAFT Acceleration is the Measure • Coordinate system established relative to torso/chest
DRAFT Acceleration Limits Figures 6-18
DRAFT Acceleration Limits Appendix X2
DRAFT Acceleration Limits Appendix X2
DRAFT Purpose of Acceleration Limits • Provide Design and Test Limits which are determined to be safe for the general riding public. — Accelerations within the limits are physiologically acceptable for the riding public — Accelerations outside the limits need further review by experts to determine acceptability • How are accelerations measured? — In design, they are calculated when possible — For existing rides, they are measured with accelerometers — ASTM F2137 – defines specifications and response corridors — ASTM F2291 – defines post-processing, 5 Hz low pass filter Slides from ASTM F-24
DRAFT Considerations given to: (including but not limited to…) • Age of riders (young and old) • Neck strength of older riders • Cardiovascular effects of negative Z G’s • G-induced loss of consciousness studies • Limiting combined axis G’s • Practical experiences — Reversals, onsets • Existing guidelines and standards (TUV, Australia, Italy, CEN proposal) Slides from ASTM F-24
DRAFT G-Limits • The G Limits are set based on the assumption that the rider is appropriately restrained: — “Rides and devices with patron containment systems shall be designed such that the patron is suitably contained and positioned to accept these accelerations.” Slides from ASTM F-24
DRAFT Restraint Design • F2291 provides for restraint standards on the basis of: — Clearance — Acceleration — Anything in F2291:6.4.4.1 — (1) Duration and magnitude of the acceleration, — (2) Height…, — (3) Wind effects, — (4) Unexpected stopping positions of the patron units, — (5) Lateral accelerations, for example, where sustained lateral accelerations are equal to or greater than 0.5 G, — (6) The intended nature of the amusement ride or device. — F2291:6.4.4.1 is a design standard
DRAFT Restraints • Restraints designed and developed in parallel with human tolerance studies 2009 1959
DRAFT Restraint Classes • Restraint types depend on acceleration, etc.
DRAFT Biodynamics • What is it? — “The study of the effects of dynamic processes, such as motion or acceleration, on living organisms.” — It’s the study of how people respond to motions and accelerations — Ride design — Ride standards
DRAFT Biodynamics • Newton’s Laws • Forces • Acceleration — Gravity (G’s) • Speed • Turning • The human body
DRAFT Newton’s Laws • 1. Inertia and Momentum — A body in motion stays in motion — A body at rest stays at rest • 2. Definition of Force — Force = Mass * Acceleration • 3. Balance of Forces — For every action, there is an equal and opposite reaction
DRAFT Force and Acceleration • Force: — Anything that causes a body to change in speed, change in direction, or change in shape. • Acceleration: — Rate of change of both the amount and the direction of velocity — In one dimension, velocity is speed, and acceleration is how quickly something speeds up or slows down
DRAFT Force and Acceleration • Force: — It takes a force to make an object move or change its direction • Acceleration: — Force = Mass * Acceleration — So changing an object’s speed or its direction creates an acceleration of that object
DRAFT Turning • Changing direction causes acceleration, too — Acceleration = velocity 2 /radius — Acceleration based on how quickly speed (v) and direction (R) change a p v This is why a c corners are banked on roller- R coasters.
DRAFT Turning • Centripetal acceleration — a c = v 2 /R a p — Double speed v — 4 a c = (2*v) 2 /R a c — Double radius R — 1 / 2 a c = v 2 /(2*R) — Double both — 2 a c = (2*v) 2 /(2*R)
DRAFT Turning • Circular speed — Distance around a circle ≈ 6.3 * R — (2 * pi * R) or (pi * diameter) — This is why the correct speed setting is important a p 1 RPM 10 RPM 20 RPM v R = 20 ft 2.1 fps 21 fps 42 fps R = 10 ft 1.05 fps 10.5 fps 21 fps a c 1 RPM 10 RPM 20 RPM R R = 20 ft 0.007 G 0.7 G 2.8 G R = 10 ft 0.003 G 0.34 G 1.4 G
DRAFT Directions +Gx -Gx +Gy -Gy +Gz From Compendium of Human Responses to the Aerospace Environment, Section 7: Acceleration, 1959, NASA -Gz
DRAFT Duration and Direction From Compendium of Human Responses to the Aerospace Environment, Section 7: Acceleration, 1959, NASA
DRAFT Human Tolerance: +X • Generally the most tolerant axis — Limited by breathing — Increased Gs make it difficult to inhale — Tolerance — Up to 10 G for a period of minutes — Fatigue is a factor You get tired
DRAFT Human Tolerance: +X
DRAFT Human Tolerance: +X
DRAFT Human Tolerance: –X • Theoretically higher than +X — Easier to breathe • In practice, considered to be lower — Restraint pain — Possible –G z issues when head flexes forward — Interferes with tearing and vision — 6-8 G reasonable limit
DRAFT Human Tolerance: –X
DRAFT Human Tolerance: –X
DRAFT Human Tolerance: +Z • Short-duration – spine-limited — Thoracic spine tolerance between 12 and 25 G, posture-dependent — 3 seconds and less • Long-duration – brain-limited — Large Gz makes it difficult to move blood to the brain — Black outs, G-LOC — 3 G can be tolerated for long durations
DRAFT Human Tolerance: +Z
DRAFT Human Tolerance: +Z
DRAFT Human Tolerance: –Z • Low tolerance to –Z — Cardiovascular response mechanisms minimal — Rushing of blood to head — Low arteriovenous pressure difference (high for both) — Headache and “red out” — -3 G is beginning of limit -5 G can be tolerated for 5 seconds with practice
DRAFT Human Tolerance: –Z
DRAFT Human Tolerance: –Z
DRAFT Human Tolerance: Y • Limited Data — Uncommon load direction — Volunteer testing usually limited by clavicle pain — Exposures to 12 G have been reported, but usually cause bruising
DRAFT Human Tolerance - Y
Recommend
More recommend
