Amusement Rides: How much thrill is too much? Robert S. Cargill II, - - PowerPoint PPT Presentation

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Amusement Rides: How much thrill is too much? Robert S. Cargill II, - - PowerPoint PPT Presentation

Dec 05, 2022 258 likes •816 views

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

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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

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  • Standards and Amusement Rides and Devices
  • ASTM International committee F24 and F2291
  • Biodynamics/Biomechanics
  • Basis for limits/guidelines
  • Quiz

Biomechanics of Amusement Rides

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What do biomechanical engineers do?

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  • EN (EuroNorm)
  • ASTM International
  • ISO (International Organization for Standardization)
  • Standards Australia
  • China

Standards-setting Bodies for Amusement Rides

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  • 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

ASTM International

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  • Engineers, biomedical engineers, doctors, regulators,
  • perators assembled in 2000-2001 to give

recommendations to ASTM for acceleration limits.

  • First USA consensus acceleration limits standard

approved 2001

ASTM F2291 History

Slides from ASTM F-24

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  • 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

The Human Body

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  • 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

Human Tolerance

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  • Many years of establishing biodynamic limits

— Air Force – forward deceleration (Colonel Stapp)

What is the measure?

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  • Many years of establishing biodynamic limits

— NASA, Air Force – acceleration “through the seat”

What is the measure?

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  • 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

What is the measure?

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  • Standard biomechanical technique to normalize force

to body mass

  • Acceleration!
  • Tolerable limits depend on

— Duration — Direction (for whole body)

Acceleration is the Measure

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  • 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

  • r velocity standards

— So what changes?

— Duration, direction, location

Acceleration

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  • Coordinate system established relative to torso/chest

Acceleration is the Measure

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Figures 6-18

Acceleration Limits

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Appendix X2

Acceleration Limits

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Appendix X2

Acceleration Limits

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  • 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

Purpose of Acceleration Limits

Slides from ASTM F-24

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  • 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)

Considerations given to:

(including but not limited to…)

Slides from ASTM F-24

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  • 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.”

G-Limits

Slides from ASTM F-24

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  • 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

Restraint Design

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  • Restraints designed and developed in parallel with

human tolerance studies

Restraints

1959 2009

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  • Restraint types depend on acceleration, etc.

Restraint Classes

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  • 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

Biodynamics

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  • Newton’s Laws
  • Forces
  • Acceleration

— Gravity (G’s)

  • Speed
  • Turning
  • The human body

Biodynamics

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  • 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

Newton’s Laws

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  • 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

Force and Acceleration

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  • 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

  • f that object

Force and Acceleration

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  • Changing direction causes acceleration, too

— Acceleration = velocity2/radius — Acceleration based on how quickly speed (v) and direction (R) change

Turning

v ac ap R

This is why corners are banked on roller- coasters.

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  • Centripetal acceleration

— ac = v2/R — Double speed

— 4 ac = (2*v)2/R

— Double radius

— 1/2 ac = v2/(2*R)

— Double both

— 2 ac = (2*v)2/(2*R)

v ac ap R

Turning

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  • Circular speed

— Distance around a circle ≈ 6.3 * R

— (2 * pi * R) or (pi * diameter)

— This is why the correct speed setting is important

1 RPM 10 RPM 20 RPM R = 20 ft 2.1 fps 21 fps 42 fps R = 10 ft 1.05 fps 10.5 fps 21 fps 1 RPM 10 RPM 20 RPM R = 20 ft 0.007 G 0.7 G 2.8 G R = 10 ft 0.003 G 0.34 G 1.4 G

Turning

v ac ap R

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Directions

  • Gz

+Gz

  • Gy

+Gy

  • Gx

+Gx

From Compendium of Human Responses to the Aerospace Environment, Section 7: Acceleration, 1959, NASA

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Duration and Direction

From Compendium of Human Responses to the Aerospace Environment, Section 7: Acceleration, 1959, NASA

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  • 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

Human Tolerance: +X

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Human Tolerance: +X

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Human Tolerance: +X

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  • Theoretically higher than +X

— Easier to breathe

  • In practice, considered to be lower

— Restraint pain — Possible –Gz issues when head flexes forward — Interferes with tearing and vision — 6-8 G reasonable limit

Human Tolerance: –X

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Human Tolerance: –X

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Human Tolerance: –X

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  • 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

Human Tolerance: +Z

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Human Tolerance: +Z

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Human Tolerance: +Z

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  • 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

Human Tolerance: –Z

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Human Tolerance: –Z

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Human Tolerance: –Z

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  • Limited Data

— Uncommon load direction — Volunteer testing usually limited by clavicle pain — Exposures to 12 G have been reported, but usually cause bruising

Human Tolerance: Y

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Human Tolerance - Y

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Human Tolerance - Y

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  • Ride standards use a safety factor

— Take the known tolerance to whole-body acceleration for healthy adult males, and build in an allowance for everyone else — The military’s definition of non-injury may differ from that of the riding population — Kids now included

Human Tolerance and the Amusement Ride

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  • A biodynamics expert can say otherwise

— “The designer/engineer shall determine whether the acceleration limits herein, or more restrictive limits, are appropriate for an amusement ride or device that accommodates patrons under 48 in. in height. In making this determination, the designer/engineer shall consider biodynamic effects on the patrons. Examples of industry practice are provided in Appendix X7 (non-mandatory)..” – F2291:7.1.4.3

Human Tolerance and the Amusement Ride

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  • Not applicable to durations of less than 200 ms

— Does not cover “impacts”

  • Limited incorporation of jerk – rate of change of

acceleration

— Effectively is included

  • Does not explicitly include rotational accelerations

— At this time, no rides have rotational accelerations high enough to be an issue

Limitations

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  • Atypical riders?

— Very young children — Elderly riders — People with disabilities

So what about…

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  • Quiz Questions:
  • The tolerance to acceleration generally increases as

the duration decreases. True or False?

  • The limits of tolerance specified in the ASTM F2291

standard rely on proper restraint design. True or False?

  • The limits are based on only physiological response

and ignore mechanical limits. True or False?

Amusement Rides:

How much thrill is too much?

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DRAFT

  • Thank you!
  • I’d like to acknowledge Bill Bussone, PE of JP

Research for his help in putting this presentation together

Amusement Rides:

How much thrill is too much?

Robert S. Cargill II, PhD, PE

rcargill@jpresearch.com JP Research, Inc. Fort Washington, PA