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Rigging I:

Transferring forces all the way down to the ground

Presentation by Steven Santos

Key points for this presentation• What forces do we need to be aware of?

– Static Load– Shock Load– Swinging Load– Spinning Load

• Rated Strength, SWL, MBS, LBS, KN, SLUG, etc• Overview of tracking forces • Week Link Analysis • Risk Assessments for Rigging• Commonly Used Mount Points• Questions!

What forces do we need to be aware of?

In the world of aerial rigging, we need to be aware of all of the forces we could possibly put on the rigging. This includes the static load, and the shock load

We also need to be aware of the directions of those forces. A static load places forces on the mount point differently than does a swinging load, and both are different from a spinning load.

What forces do we need to be aware of?

When it comes to aerial rigging, we are generally concerned with four classes of force:

– Static Load– Shock Load– Swinging Load– Spinning Load

Static Load

• A Static Load is a load that does not change.

– Examples of static loads include • Lyra

• Static Trapeze

• Aerial Silks (except drops)

Shock Load• A Shock Load is the resulting load from the

rapid change of movement, such as impacting or jerking, of a static load. A Shock Load is generally significantly greater than the static load.

• Examples of Shock loads include • Drops

Swinging Load• A Swinging Load is a load that is in motion

horizontally. By definition, Swinging Loads cause side loading of the mount point. In a straight swing, the highest loads are at 4:30 and 7:30

– Examples of swinging loads include:• Swinging Trapeze• Flying Trapeze• Some Aerial Silks• Swinging Lyra

Spinning Load• A Spinning Load is a load that is in constant

rotation. By definition, Spinning Loads cause side loading of the mount point in all directions.

– Examples of swinging loads include • Cordless Lisse• Spanish Web• Some Silks Skills

Strength Terms

• Rated Strength is the strength the manufacturer has determined the equipment should take.

• SWL = Safe Working Load. SWL is one way that manufacturers rate strength. SWL*safety factor=MBS

• Safety Factor is a number that the tensile strength is divided by in order to determine the safe working load

• MBS = Mean Breaking Strength. MBS is the average breaking strength the equipment is tested to.

Weights and ForcesOne of the difficulties with rigging circus apparatus is that we end up using rigging components from many different industries, almost none actually designed for how we use them. Some equipment uses the S.I. system, where weight is expressed in kilograms (a mass), newtons (a force) and kilonewtons (a force with mass). Other use the English system, where weight is expressed in pounds (a force with mass).

When dealing with rigging components, it is often helpful to convert everything to use one numbering system or the other.

Overview of Tracking Forces

When ever we set up rigging, we want to start by checking over the mount point, and follow the forces all the way down to the ground.

DO NOT ASSUME ANYTHING

• Is the horizontal beam strong enough for what we want to do?

• Are the vertical beams strong enough for what we want to do?

• Is the connection between the vertical and horizontal beams strong enough for what we want to do?

• How does our mount point deal with horizontal forces? Is it strong enough for what we want to do?

• If it is not strong enough, how do we make it strong enough?

Weak Link Analysis (WLA)

WLA is the process of systematically examining each and every component of a rigging setup to find the weakest link.

Once identified, rigging is designed and built with the weakest link in mind, and with the desired safety factor.

Risk Assessments for Rigging

A Risk Assessment for Rigging

is done much like any

other Risk Assessment.

Striar JCC Points 1 – 5 Risk Assessment / WLA

Silks Risk Assessment / WLA

Likelihood / Severity

0 Extremely Unlikely

1 Unlikely2 Possible3 Likely4 Very Likely

0 Ext. Insignificant1 Insignificant2 Minor3 Moderate4 Major

Commonly Used Mount Points

• Roof Trusses– Snow Load

• Freestanding Rigging Frames

• Floor Trusses– Excess Capacity

Questions

Silks Rigging

Lyra(Single Tab, Single Point)

Lyra Rigging (Two Tabs, Single Point)