Radius
Also called Working radius
In crane terminology, the horizontal distance from the crane’s centre of rotation to the centre of the load being lifted. A crane’s safe working load reduces as radius increases, which is why radius is one of the two key figures — with the resulting load — read from a load chart.
In practice
Radius is measured from the centre of slew to the centre of the load, not from the front of the machine or from where the operator is sitting, and it is the horizontal distance — not the length of boom out to the hook. Both mistakes flatter the lift, because both understate the true radius.
Where this comes from: Standard crane terminology; the capacity-versus-radius relationship is on the load chart for the machine.
Where it matters on site
Radius also moves the ground loading around. Working further out shifts more of the total onto the outriggers on that side, so the worst-loaded foot is a function of radius and slew together. When a lift is re-planned to work at a longer radius, the mat under the leading foot is part of what has to be re-checked.