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vRigger Learning Center

This also applies to cable, chain, and webbing.

Gear that is anchored includes anchors, rocks, trees, tripods, trucks, etc.

A "bight" is a simple loop in a rope that does not cross itself.

A "bend" is a knot that joins two ropes together. Bends can only be attached to the end of a rope.

"Descending devices" (e.g., ATCs, Brake Bar Racks, Figure 8s, Rescue 8s, etc) create friction as their primary purpose. The friction in descending devices is always considered when calculating forces.

The "Safety Factor" is the ratio between the gear's breaking strength and the maximum load applied to the gear (e.g., 5:1).

Troubleshooting Force Calculations

Calculating the forces on an infinite number of systems is a daunting task—both for a computer program and for an individual. This page explains a few of the situations where vRigger may not display the results you expect.

Choose a topic:

If the above information doesn't resolve you question, read how you can get help on force calculations. You can also learn more about rigging forces.

The displayed forces do not appear to be correct

The vRigger engineers have gone to great lengths to see that vRigger calculates forces correctly, but there are systems that do not have a static solution and some that vRigger can't solve. See Incorrect Force Calculations for tips when the results don't look correct.

The system ... is not balanced

The Unbalanced Forces dialog may be displayed when a system cannot be solved. Learn more about systems containing unbalanced forces.

Force information is not displayed

Force information cannot be displayed unless the forces have been calculated. If you modify the system in any way, the forces will no longer be valid.

Force labels can be displayed near each piece of gear, in ScreenTips, and on the status bar. Learn more about displaying forces.

System not solved in n seconds

This message is displayed if it is taking longer than expected to calculate the forces. You have the option of canceling or continuing the calculations. You can always stop the calculations by pressing Escape.

The force on the ______ has exceeded its maximum force

This message appears when the force on gear that can pull or release has exceeded its maximum force. Refer to the Forces (pull/release) section in the properties pane.

Only one item can pull on a rope

vRigger can't solve a system when more than one item can pull on rope. If more than one item can pull, all of the pullers will be treated as if they are anchors (i.e., they will hold the rope stationary).

Getting help with force calculations

If you encounter a force calculation problem that you cannot resolve, or if vRigger is unable to correctly calculate the forces in your system, you can send the *.rig file to info@vRigger.com with a short note explaining the problem you encountered and any messages that were displayed. Like most people, we are constrained by time, but we'll try to look into it.

Learn more about rigging forces

Learn about rope rescue physics and mechanical advantage at RopeRescueTraining.com.

Watch a video that explains how to calculate forces.

REMINDER: The force calculations in vRigger are calculated based on a static, two-dimensional computer screen—the values can vary in the "real world." It is your responsibility to understand the strength of your rigging systems.