ST171 · Forces in a Crane Jib

Experimental apparatus for the vectorial analysis of forces in a planar concurrent system — crane-jib model

A simplified model of a wall-mounted jib crane: a horizontal compression bar and a chain tie meet at the load-application point, where a calibrated weight is suspended. Spring balances integrated into each member read the tensile and compressive forces directly, letting the student compare the measured values against the result of a force parallelogram and an analytical solution. Because the geometry of both members is adjustable, the dependence of the bar forces on the jib geometry can be swept experimentally.

Experiments

Graphical breakdown of forces by force parallelogram
Determination of the bar forces (tensile and compressive) for various jib geometries
Three-way comparison: measured — graphical — analytical
Influence of bar length and chain angle on the bar forces
Distinction between tensile members (chain) and compressive members (strut)

Apparatus

Crane-jib model adjustable-length bar + chain tie, clamped to a vertical retaining column

Retaining column stainless steel

Base sturdy metal plate with transport handles

Max applied load 50 N

Measurement

Tensile spring balance 0…50 N, graduation 0.5 N (integrated into the chain member)

Compressive spring balance 0…50 N, graduation 1 N (integrated into the bar)

Load set

Weights 1 × 1 N hanger · 4 × 1 N · 1 × 5 N · 4 × 10 N

Delivery

Experimental unit — base plate, retaining column, jib bar, chain
2 spring balances (1 tensile, 1 compressive)
Complete weight set
Storage case with foam inlay, instruction manual

10 kg