Two Point Anchor Loads
Most people understand that a load can be shared by two points. If the two anchors are directly above the load and equalised, they each feel half the load. Many people also know that if the two anchor points are horizontally separated, each anchor point feels more than half the load. In this case, the load is effectively magnified. While recognising this phenomenon, many people struggle to understand why this is the case. The following video offers an explanation which may help people to understand the physics in this situation.
Note that Richard uses arrows as vectors to represent forces. Both their direction and magnitude, or length, are relevant. Please see this RopeLab article to review the use of vectors.
You will also note that the process of adding the horizontal and vertical vectors creates a diagonal vector and as a result, a right-angled triangle. We could use trigonometry here to calculate the value of angles and lengths of sides representing the vectors. However, Richard chooses to draw the triangles in and visually estimate the length of the sides to get an idea of the size of the forces involved. This is a technique that can be used quickly and easily in the field.
© Richard Delaney, RopeLab, 2016
About The Author
Richard Delaney
Richard Delaney has worked professionally with ropes since 1992 as a multi-pitch rock-climbing instructor, technical rescue instructor and rope access technician. Understanding and teaching the Physics of Rigging is a core passion of Richard’s, one based on his experience, and his prior professional life as a qualified engineer.