Deflection of Free-standing Jib Crane

[chairat1967]

I have an issue regarding the deflection of free-standing jib crane. This jib crane is designed for lifting the automotive parts,its weight is approx.300 kg, This jib crane uses 8"-pipe sch.40 as a post(4,500 mm high) and KBK light track as a girder(4,000 mm long) and uses 2"-pipe as a stay support between its post and the end of girder. From the calculations the stress of each component are less than their allowable stress.
After installation and load testing with 300 kg, the max. deflection is 30 mm or L/133(L = length of girder from supported point to the end of girder). Is this deflection is acceptable? as some manufacturers's deflection design guidelines are L/150(which is about 26.67 mm for this jib crane)

Best Regards

Chairat Sracoopun

 

[fegenbush]

I recommend you calculate the force required to move the load radially inward (uphill) with that deflection. Include friction in your calculation. You may find that deflection unacceptable as the load will be difficult to move uphill, and will want to move downhill should the load be placed somewhere other than the end of the beam. A common criteria for deflection of crane beams that I have seen is L/500 due to the load moving uphill/downhill.

 

[DamsInc]

"Design Concepts for Jib Cranes" by Fisher and Thomas recommends L/225.