Rigging
Math
(Made
Simple)
A
Primer by
Delbert
L.
Hall, Ph.D.
ETCP
Certified
Rigger
ETCP
Recognized Trainer
Introduction
There are plenty of
entertainment riggers who do not know how to do much math - but these
are the
people doing exactly what they are told to do, and not the ones
figuring out
what to do and doing the telling. If you want to be a
top-notch rigger,
you have to know math. Math does not have to be
hard. It is a lot
like cooking - you need a good recipe, and then you just have to follow
it -
EXACTLY. The purpose of this site is to provide you with the
recipe for
solving rigging problems. Once you learn the recipes - uh,
formulas - you
will be able figure out many rigging problems.
While
each lesson in the primer contains some explanatory information on the
problem
covered in that lesson, this information is not intended to be lesson
on
rigging. This is
not a rigging
primer. The lessons
are not
intended to teach the concepts or principles of rigging, they teach the
math
needed to solve a particular rigging problem. Users
should already have a basic understanding of stage
rigging. This
primer was created
for individuals taking a rigging class or seminar and preparing to take
a rigging
certification exam, but anyone wanting to solve a particular rigging
problem
(that involves math) might benefit from these lessons.
Getting
Started
Now, before you start going
crazy and start screaming "I can't do math!" - relax. Most rigging
math is no more complicated than doing simple addition, subtraction,
multiplication
and division - the stuff you learned to do in elementary
school. What's
more, you can even use a calculator to help you do the math.
I highly
recommend the TI-30XA scientific calculator for this rigging primer.
This
calculator is inexpensive (under $15), available at Wal-Mart and nearly
all
office supply stores, and is easy to use. But why a
"scientific
calculator?" Well, there are a few rigging problems that are
just A
LOT quicker and easier to solve by using scientific functions than by
using "simple
math." But relax - the examples in this primer will take you
through
examples, step by step. So, get yourself a TI-30XA scientific
calculator.
TI-30XA
Calculator
Once you have it, go to Learning
to use your TI-30XA Scientific Calculator,
where I cover the basic operation of the calculator that you will need
to
know. This page also introduces you to some of the
conventions that I
will use later in the lessons when I describe how to use your
calculator to
solve particular problems. Once you are familiar with the
calculator, you
are ready to start your Rigging Math Lessons.
Note:
While you can to do the lessons in any order, or just
pick a lesson that covers a problem that you need to solve, the earlier
lessons
use the simplest math and are designed to introduce you to some of the
terms
and concepts that are used in some of the later lessons. If
you are
relatively new to rigging math, it is suggested that you do the lessons
in
ascending order.
What
to Expect
Each
lesson
begins with a general explanation of the problem, where you would
encounter
this type of rigging problem, and how you would go about solving the
problem. Some rigging problems are best understood
graphically, so in many
cases there will be an accompanying drawing or schematic of the
problem.
This is then followed by the formula (equation) used to solve the
problem. (It should be noted that there are sometimes several
equations,
or variations on an equation, that can be used to solve a particular
problem. If you know a different equation than the one that I
am using,
and that equation works for you, use it. I will use the one
that works
best for me.) Next, I will work through a sample problem in
detail and
show how to get the correct answer. Finally, at the end of
each lesson,
there is a link to a ÒworksheetÓ of similar problems. This
page will have
a link to the answer sheet, so that you can see if you get it correct.
Some problems are pretty simple, while others may require multiple
steps
(calculations). It is a very good idea to have scratch paper
and a pencil
at all times so that you can record the solutions to each step, as you
work
them out.
Conventions
Each
formula (equation) includes variables. The most common
variables used in
this primer are:
L
= Leg of a bridle or Leg supporting one end of a beam (truss)
H
= Horizontal distance
V
= Vertical distance (height)
D
= Distance (usually a horizontal distance)
In many cases you will see a number (most often either a "1" or a
"2") following the letter (L1, L2, H1, H2, V1, and V2 are common
variable names) in problems involving bridles. The number is
used to
designate which of the two bridles is being referenced. The
accompanying
schematic will also aid in helping you understand the problem. Other
common
variables such as Load and Span are fairly self-explanatory.
Last, I have already stated that we will work through a sample problem
each
lesson, but it the early lessons, where I tell you precisely which keys
to
press on your calculator, I denote the non-numeral keys to be pressed
by
putting them in square brackets. [X] the times key, [Ö] the divide key,
and
[SIN] the Sine are some of the keys that I indicate in this
fashion.
A few
more
things
In the "real world," you can use rigging calculators, like RigCalc, that contain the formulas for solving specific rigging problems. All you need to do is enter your data. However, if you are using this primer in preparation for taking an ETCP exam, you will need to memorize the formulas for solving different rigging problems for the exam, so start now. You can still use RigCalc to check your answers. Practice, practice, practice is best way to learn the formulas. I have prepared a cheat sheet with all of the formulas used in this primer. You can print it out and keep it handy for when you need to refresh your memory on a particular formula. Good luck and enjoy the lessons.
If you need some basic math help with order of operations, go to MathGoodies.
This site will help you understand how to evaluate a formula and
determine the order in which operations should be performed.
Lessons
Lesson
1: Converting
between Imperial and Metric
Lesson
2: Resultant
forces
Lesson
3: Bridle
lengths
Lesson
4: Tension
on Bridle Legs
Lesson
5: Tension
on a Horizontal Breast line
Lesson
6: Dead
hang tension on one end of a truss
Lesson
7: Center of
Gravity for two loads on a beam
Lesson
8: Leg
Tension on a Beam (Simple)
Lesson
9: Leg
Tension on a Beam (Distributed)
Lesson
10: Leg
Tension on a Beam (Complex)
Lesson
11: Shockloads
Lesson 12: Fleet Angles
Lesson 13: Three-Point Bridle Lengths
Lesson 14: Tension on Three-Point Bridles