Ground Rigging Reference of Terms and Practice
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TERMINOLOGY
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Steel
"aircraft cable"
3/8 and 1/2 inch in lengths from 2' to 50'
Shackles
Bell and pin
5/8, 3/4, and 1/2
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Deck chain
Magic making adjusting chain in 3 inch lengths (10 links normally) This is also known as STAC chain.
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Baskets
Open or Closed. Open is always 2 shackles, primary and secondary. Closed is always one shackle.
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Apex
The junction point where all rigging meets. The motor hook connects to this point. In an open or closed basket, this is also the primary shackle. In a bridle, this is the shackle the motor connects to, which hangs down from the deck chain.
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Secondary
Or secondary shackle. This is the “loose” or “free” shackle that the free end of the thimble will connect to up top. This always should be opposite of the “pin side” of the primary shackle.
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Bridle
These are used to zero a point in between 2 beams. Made up of two “legs”. They vary in size depending on location.
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Stinger/Down
This is a piece of steel of any length. It hangs down from the bottom of a basket. The motor hook connects to this.
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Dog Bone
A 2’ piece of steel. Usually is used to make up a 7 split.
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Grid
This is what we have at the Aud. Made up of horizontal grating. Almost always use pipe and closed baskets to attach the rigging to it.
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Rigging Pipe
Varying lengths of 3 inch schedule 40 pipe. Used when rigging from a grid.
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7 Split
Mostly used at the Arena, it is a special basket made of 2 shackles, a 5’, and dog bone or 2 ft of deck chain. We rig these to the big H-beams.
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Low Steel
Any steel that is under the up rigger’s feet. At the Arena, they are marked with 2’s and 0’s
High Steel
Any steel that is over the up rigger’s head. At the Arena, they are marked with 1’s and 3’s
Bowline
The knot we use when pulling baskets and bridles up. The size will very depending on the application. Remember, high steel should be 1 foot, and low steel should be half the length of the basket. Know this knot, if tied improperly, it can come untied and the rigging will fall and hurt some one badly.
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Clove
The knot we use when tying to a pipe or securing a load, such as a video screen, to a railing.
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Arbor
This is where the counter weight goes for the system pipes at the Aud.
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Batten
This is the name of the system pipe at the Aud.
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Bull Line
This is tied to a system pipe when over-hauling an out of weight load, or to control an out of weight load as it goes out until the load can be weighted properly.
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Proscenium
The large decorative opening downstage in a theatre.
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Chain Motor
Mechanical object used for hoisting heavy objects.
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Block and Fall
A block and tackle is a system of two or more pulleys with a rope or cable threaded between them, usually used to lift or pull heavy loads.The pulleys are assembled together to form blocks so that one is fixed and one moves with the load. The rope is threaded, or reeved, through the pulleys to provide mechanical advantage that amplifies that force applied to the rope.
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Fall Arrest Sheave Bunny Ears Invert Thimble
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Pythagorean Theory: A2 + B2 = C2
Distance to the beam from the apex
Height of the hook of the motor in relation to the floor
How it works
2 upside down right triangles
90 to 120 degrees
What it looks like on the ground (written) Basic bridle
1/2 ton, 1ton, 2ton.
High steel and high low
Sound and Video (triangle/square).
Implementation
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Building the point
Steel lengths
Red = 5'
White = 10'
Blue = 20'
Green/Yellow = 30'
Yellow = 50'
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Start at the apex
Build the bridle from longest to shortest. The last piece before the basket should be the shortest (deck chain is always closest
to the basket).
Coil as you go.
Keep the steel as compact as is reasonable. Each leg of the
bridle should have its own coil.
Finish with the basket
Don't fuck the up riggers! Assembling the basket correctly is
the deal maker for the point. Do it the same way every time!!! Hold the shackle by the thread side, pin out, opening up.
Place the "free", "loose", or "down" shackle first
(through the bell!!).
Place the basket thimble over the shackle next.
Pin through the thimble (link) of the bridle leg.
Don'ts
Over-tighten shackle pins
Pin up on the bridle leg
Pinch links
Do's
INSPECT EACH ITEM!!
Broken wires in cable
Sprung cable
Crosby/Chicago shackles. NEVER rig with Chinese
shackles!!!!
Frayed ends
Damaged swedges
Double check your work.
Are the legs the right length?
Is the orientation correct?
*The arena floor is a very noisy place, and most of the
noise rises into the steel and bounces around. Keep your
calls simple and precise. The fewer words the better. This is no time to carry on a conversation. You, as the ground rigger, have the potential to cause or prevent a tremendous amount of harm. Pay attention to what's
going on, both around you with the rest of the crew as well as overhead. The only acceptable knot is a bowline. Period. No exceptions, regardless of what you think or how much you know.
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Tying in
Call up "what do you want?" (call down "Three footer no bag!") Use your body to measure out the loop in the knot.
Always tie into the pin side of the basket shackle. Period, no exceptions.
Have at least a 6 inch tail on your bowline.
Have the rigger take weight, "Hold that", when the opposite rigger has the same weight, call out "together!!"
Watch the steel out, looking for turned shackles, knots in the
steel, the facing of the hook, the pull on the chain.
*Make sure the area is clear before calling
"together". You have the responsibility to protect your fellow crew members from swinging steel and chains. They have
their own job to do and you have yours. That job is part of yours.
Lowering
Listen and watch
Listen for a call from the steel, such as "Deck rigger up right!!!
Watch for a shaking chain (the rigger will wiggle the point to
help you find it)
Position yourself to effectively get the chain in the box AS IT COMES IN.
Pull gently on the chain as it comes in, countering the friction of the rope on the beam
Remember, you are responsible for the safety of the crew around you: CONTROL THE ACTION
When the hook is chest high, stop the drop and remove the hook (drop it in the box)
Pull in one bridle leg at a time, the safest first
The safest leg is the one furthest away from the activity on
deck.
If you have to, pull the entire bridle to an empty spot on the floor, away from the crew.
IF YOU CAN'T CONTROL THE BRIDLE BY YOURSELF, GET HELP!!!
It takes seconds to stop the descent, get a person on each leg
of the bridle, and protect the crew.
Things to know
Three sizes of beams on the "low" (65') steel.
Main- the big "H" beams running across stage
Mains are 50' apart
Use a 10' basket or split (5/10) basket
There is 3 1/2 feet of "layback" (distance to the basket shackle) from the beam with a 10' basket.
Secondary- the "double angle" beams running up and down stage.
Secondary's are 50' apart
Always use a 5' basket
Tertiary- the smallest beam in the arena, running parallel to some mains
25' from the main
Always use a 5' basket
High steel
There are two size beams at the high steel
High Main
Directly above the low mains
Mains are 50' apart
Use a 10' basket or split (5/10) basket
There is 3 1/2 feet of "layback" (distance to the
basket shackle) from the beam with a 10' basket
High
Run up and down stage
The beams are 25' apart
Always use a 5' basket
Always use a "zero" bowline
The rigger is hanging from the harness when working high steel, lacking leverage.
Split baskets
A split basket is used on the upstage mains where there is no "low safety"
To build
Hold the basket shackle tread side, bell down
Place the 10' steel, then the 5' steel.
Pin the last thimble (link) on the bridal leg
Place the open thimble of the 5' (FIVE FOOT!!!) basket
leg in the bell of the "loose" shackle.
To tie in
Tie into the thimble of the 5' basket leg behind the loose shackle
A bowline is the only acceptable knot. Period.
Take tension against the rigger when going out over the seats, to prevent the steel from getting caught between them.
Dead hangs
A dead hang is simply a one legged bridle
Build the dead hang the same way
Be careful not to hook into the basket!!!
Never place the chain directly under the point, it tangles the rope and chain
Layout
Most shows pull every motor out of the box near the point. Grab the chain near the motor and pull straight up and
out (if there are handles, use them)
NEVER pull from the cable
Lay the motor on its long axis, with the bag side down (where the chain goes into the bag)
Pull the chain to the motor from the box
The chain should pile up with the hook last, so
there's no additional weight and the rigger's not
pulling from under the pile.
In a perfect world, you have the point, the diagram, the coiled steel (in the right orientation), the chain pile and the motor, in that order
2 tons
A 2ton is a really heavy 1ton and should be treated as such but for the following exceptions
The bridle and basket are assembled out of 1/2 inch steel cable
(as opposed to 3/8 we normally use)
Each bridle will use 3 (three) 3/4 shackles along with the regular 5/8, everywhere there is more than one pull
The apex
Each basket shackle (NOT the loose shackle)
The chain must be "evened out" before being put in the box.