![]() If this continually changes the beam could fail under fatigue stress and so the lifetime of the crane will be dependant on the ability to withstand this factor. The bearings at A and B exert only vertical reactions on the shaft. Example 1 Draw the shear force and bending moment diagrams for the beam shown below a) determine the reactions at the supports. Draw the shear and moment diagrams for the shaft and determine the shear and moment throughout the shaft as a function of x for 0 x 6 3 ft, 3 ft 6 x 6 5 ft, and 5 ft 6 x 6 6 ft. It can be seen from the Diagrams shown that higher shear forces and bending moments will be present towards the location of the load. A bending moment diagram is one which shows variation in bending moment along the length of the beam. Fatigue will be cause by continually changing loads on the crane. With constant movement of loads across the vertical beam fatigue could be an issue. Reqd: Determine the shear force and bending moment distributions. The beams researched are used in portable gantry cranes and are light weight with the sole purpose of manual assembly. 12 - Fishback wire strand, 14 - Steel wire rope core, 16 - Synthetic fibre rope core, 18 - Outer steel wires. The crane is lifting an object of mass M 1000 kg. The weight of the beam has been selected from existing beams. ![]() Allowing the same maximum shear stress in the bolts as in the shafts. At this point the loads will be exerted on the method of joining and could create loads unsustainable by the joining method. A beam AB is lifted by two slings of unequal lengths, attached at their lower ends. 4. A 4metre beam will not be able to be transported manually and therefore a break will be present in the finished crane. The problem which may arise during practical use of the gantry is at the midpoint. The beam length will have to extend past the 4 metre distance required to move the load and so 4.2 metres has been selected. I have illustrated the shear force and bending moments on the beam. Depending on the location of the winch loads and stresses will vary. ![]()
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