Outreach

Outreach is the horizontal distance from the axis of rotation of the unit to the centre of the load attachment. It is not the same as the length of the jib: a trolley reaches neither the very end nor the area right next to the pillar. The usable outreach is therefore smaller than the overall dimension, and close to the axis there remains an area that cannot be reached.

On articulated-arm units the outreach is not a fixed figure but a range between the folded and the extended arm. The articulated arm also reaches points near the pillar and behind obstacles.

What governs is the point furthest from the pillar – measured to the centre of the gripper in the position in which the load is picked up or set down there. An allowance is added for pallets and containers that are not placed exactly.

The nearest point matters just as much: if a set-down position lies close to the pillar, a unit with a large dead zone is ruled out. The simplest tool is a plan view of the workstation showing the pillar position, all pick-up and set-down points and the obstructions.

Outreach enters the tilting moment linearly: double the outreach, double the moment on pillar and floor. The deflection of the jib grows much faster. For a cantilever with a point load at the end it rises with the cube of the length – eight times for double the length and the same cross-section.

A longer jib therefore needs a stiffer and heavier section. The operator feels this: more mass has to be accelerated and braked when slewing. A unit ordered a metre longer “to be safe” is the more sluggish one in daily use.

Outreach and slewing angle together give the working area. A free-standing pillar unit can slew all the way round, depending on design; a wall-mounted unit typically covers about a semicircle. But machines, columns and racking stand in that area, and the jib also sweeps over zones where nothing is lifted.

If a slewing unit does not suffice or would have to become unreasonably long, a rail system is the alternative: it covers a rectangular area without putting a moment into the floor.