How to use the spreader beam load calculator
A spreader beam holds two pick points apart so the lower slings hang close to vertical. Even with only two pick points the loads are rarely equal, because the center of gravity is seldom exactly halfway between them, so the beam and the slings always have to be chosen for the heavier side.
The split follows the lever rule: left pick point load = total weight ร (spacing โ CG distance) รท spacing, and the right pick point carries whatever is left over. The pick point nearer the center of gravity always takes the larger share.
Top sling tension is the pick point load divided by the sine of the sling angle, so it climbs quickly as the legs flatten. At 60 degrees from horizontal a leg sees about 1.16 times the load, at 45 degrees about 1.41 times, and at 30 degrees a full 2 times. The horizontal component of that same force compresses the beam, which is why a steeper angle helps the beam as well as the slings.
These figures are a pre-check to read against the load chart, not a substitute for it. A spreader beam is only rated for the capacity and span combinations published by its manufacturer, and the final rigging arrangement should be reviewed by a qualified rigger or lifting engineer before the pick.
Frequently asked questions
The pick point farther from the center of gravity carries less. Left load equals total weight times (spacing minus CG distance) divided by spacing; the right pick point carries the remainder.
Tension rises fast as the top slings flatten out. At 30 degrees from horizontal each leg sees twice the pick point load, so keep the angle at 30 degrees minimum and ideally 45 to 60 degrees.
No. A spreader beam is only rated for specific capacity and span combinations on the manufacturer load chart, and the lift plan should be reviewed by a qualified rigging engineer.