Spreader Bar vs Lifting Beam Below the Hook
Top sling tension, spreader-bar axial compression, lifting-beam bending moment.
Example
You enter
- Total load (lb) 10000
- Bar length, pick to pick (ft) 10
- Top point height above bar (ft) 6
You get
- Sling angle at bar end 50.19
- Top sling tension (each) 6509 lb
- Spreader bar compression 4167 lb
- Lifting beam moment 25000 ft-lb
Checked against published worked examples from: ASME BTH-1 / B30.20.
Details, formula, and sources
ScopeTop sling tension, spreader-bar axial compression, lifting-beam bending moment, and headroom for a wide load from one hook. ASME BTH-1 / B30.20 and the rating plate govern.
Formula or tablesling_angle = atan(top_height / (bar_length/2)); top_sling_tension = (load/2)/sin(angle); bar_compression = (load/2)/tan(angle); beam_moment = (load/2)(bar_length/2); headroom = top_height.
Source and editionASME BTH-1 (Design of Below-the-Hook Lifting Devices) and ASME B30.20 by name; first-principles statics.
Free accessASME BTH-1 and B30.20 are published consensus standards. The statics are public.
What governsEstimate. Head rigger and manufacturer working-load-limit charts govern. Inspect every piece of hardware before the show.
API field namesload_lb, bar_length_ft, top_height_ft, sling_angle_deg, top_sling_tension_lb, bar_compression_lb, beam_moment_ftlb
- Load split load split equally to two end pick points (W/2 each)first-principles