EDCON 2018: RIGGING
RIGGING SIDEBAR: IS MY RIGGING STRONG ENOUGH?
A Ridiculously Oversimplified Introduction to
Understanding Equipment Strength
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HOW STRONG DOES IT NEED TO BE?
When you use a piece of equipment for aerial
performance, you are imposing loads and forces on
it that are much greater than just the weight of the
performer and apparatus. These include dynamic loads
caused by movement (including “drops”), resultant
forces, and sometimes extreme forces produced by flat
bridle angles. It is important to know, at least generally,
how much force your performance generates in
normal circumstances. The ANSI standards call this the
“Characteristic Load.” A typical fabric act, when dead-
hung from a single point with a recreational performer
of average weight and skill, can typically generate a
Characteristic Load in the neighborhood of 500-800
lbs./force, but it could generate significantly more. So
the first step, always, is to know your loads.
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HOW STRONG IS IT? EQUIPMENT RATING AND
MARKING: As a place to start, we need to know
how much of a load our equipment is built to hold, and
the best source for that information is the people who
designed and built it.
§4.7.2 Purchased load-bearing hardware shall either
have a marked load rating, grade rating, or have
an identifying marking that corresponds to catalog
listed ratings, or be supplied with documentation of
its strength, working load limit, or ultimate breaking
strength. ANSI Standard E1.43 – 2016 Performer Flying
Systems
The Working Load Limit (WLL – sometimes indicated
as Safe Working Load – SWL, or Allowable Load) refers
to the maximum WEIGHT of the performers and
apparatus that the manufacturer says you can put on the
equipment or structure.
While stuff built for industrial use usually has a Working
Load Limit, stuff built for climbing, rescue and related
uses often shows only the Minimum Breaking Strength
(MBS, sometimes indicated as BS or UBS). These
manufacturers are assuming that the users are experts
who are competent to determine the appropriate
Working Load Limit for their use.
Circus Arts Therapy® Trainings:
For those interested in using the
Circus Arts to compliment your
program or practice to help others
Aerial Teacher Trainings:
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WHAT DOES THIS MEAN TO ME?
Obviously, you should never intentionally load a
piece of equipment to anywhere near its Breaking
Strength. We use a number called a Design Factor
(sometimes also called a Safety Factor), to create a
clear relationship between our WLL and the BS of the
equipment. Design factor is the ratio of the load limit
(WLL) to the Breaking Strength (BS).
§4.7.3 Load-bearing hardware shall be designed and
selected with a minimum design factor of 10X WLL, 6X
characteristic load and 3X peak load.
This training, with the potential for
certification, is for teachers and
students who want to ensure that
their studio adheres to the highest
safety standards
Offering nine-month programs
in contemporary circus artistic
creation and skill development in
Portland, Oregon.
Visiting artists always welcome.
All trainings are led
by Carrie Heller,
MSW, LCSW,
RPT, co-founding
member of AYCO,
Author of the Aerial
Circus Training and
Safety Manual in
Atlanta, GA
We are proud to be the first Teacher
Training Program in America to be
recognized for our excellent standards.
celebrating 10 years
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Example 1: If your hardware has a breaking strength of
5,000 lbs/force. (or just over 22 kN), and you apply a
design factor of 10, you would have a WLL of 500 lbs.
and a limitation on characteristic load of 833 lbs.
Example 2: If you know that your performance is going to
generate a characteristic load of 800 lbs. or so, and you
apply a design factor of 6, you would need equipment
with a minimum breaking strength of 4,800 lbs.
Note: The term “Peak Load” in the ANSI Standards means
something different and more complicated—usually
related to worst-case failures in automated systems—
and is beyond the scope of this article. For most typical
manual rigging, think of the biggest possible dynamic
load which could occur if something goes wrong, and use
that as the Peak Load.
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