Articles

Rigging (9)

  1. A Good Rigger's Skill Set
  2. A Rigger's Values
  3. Becoming a Rigger
  4. Qualifications & Licensing
  5. Rigging Associations
  6. Salary Profile of a Rigger
  7. What a Rigger Does
  8. What a Successful Rigger Knows
  9. What is a Rigger?

Tips & Advice (7)

  1. House Movers Depend on Heavy Load Moving Equipment
  2. Keeping Up with Federal Regulations
  3. Keeping Your Small Rigging Business Afloat - Part 1
  4. Keeping Your Small Rigging Business Afloat - Part 2
  5. Specialized Insurance
  6. Successfully Completing a Rigger Job Application
  7. Tips for Choosing a Rigger

Trends (4)

  1. Becoming an API Qualified Rigger
  2. Helicopter Rigging & Lifts
  3. Market Opportunity? Bakken Formation
  4. Understanding Rigging Design Factors

Safety (10)

  1. Critical Lift
  2. Estimating the Capacity of Chains & Hooks
  3. Evaluating Your Load's Weight
  4. Lifting People Safely
  5. Non-Critical Lift
  6. Rigging in the Aftermath of a Natural Disaster
  7. The Dangers of Shock Forces
  8. The Problem of Moving a Load with 4 Skates
  9. Who Sets the Standards for Safety?
  10. Why Does a Rigger Need Insurance?

How it Works(13)

  1. Center of Gravity
  2. Chain Slings
  3. Gravity & Rigging
  4. Hand Signals
  5. How It Works: Mobile Cranes
  6. How It Works: Stationary Cranes
  7. Lift Planning
  8. Nylon for Slings
  9. Rotational Resistant Wire Rope
  10. Spreader Bars
  11. Synthetic Rope
  12. Understanding Hydraulic Cylinders Part 1 - Single & Double Acting
  13. Which Sling is Right for the Job?

Center of Gravity

Introduction
There are some pretty complicated explanations of the center of gravity of a load. Complex mathematical ways are available to determine the center of gravity of any load. As riggers, all we care about is where the load's center of gravity is located.

Why Is The Center of Gravity Important?
Balanced lifts are inherently more stable in flight. Knowing the location of the center of gravity of a load is important in order to make a balanced lift.

Simple Definitions
The center gravity of a load is the single point on the load at which it can be hoisted perfectly balanced. Some riggers like to think of it somewhat in reverse: it is the point at which all of a load's weight is concentrated. When performing a lift, they see it as counteracting this concentrated weight at exactly the right spot.

It Is Not Rocket Science
Sometimes finding the correct pick point for a load, or in other words, the center of gravity, is pretty simple. A load that is uniformly consistent in cross section along its length will have its center of gravity located exactly half the length of the load. This is because uniform cross sections result in uniformly distributed weight.

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How to Find the Center of Gravity by Trial and Error
Lifting problems can arise when loads have unevenly distributed weight. When it is obvious that the load does not have uniformly distributed weight, the following step by step method can be used to locate the center of gravity by trial and error:

  • Make attachment(s) to the load based an estimate of the location of the center of gravity
  • Slowly remove hoist slack and lift the load just enough to observe for any rotation
  • If the load is stable, continue with the lift ◦ If the load is unstable, move the attachment point toward the load's low point and make another trial lift
  • Continue this method until the load remains stable.


Loads Rotate Around Their Center of Gravity
It is a known fact that loads, given the opportunity, will rotate around their center of gravity. This leads to some simple, but important, hoisting rules.

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