Estimating Mobile Crane Power Needs

13 December 2018

Crane trucks aren’t haphazardly assigned to lifting projects, not when safety is on the line. Potential candidates are assessed first, evaluated to see if they satisfy fundamental load requirements. Mobile crane power is the primary factor in this instance. This power estimating methodology references key mechanical attributes on and around the crane, with boom length and chassis base forming the dimensional elements of special relational power supply equations.

Identifying Key Load Points

In order to estimate load limits, the areal distribution of the truck chassis is used. We say this is a constant, but it can vary when outriggers are fitted. Other influences here include the braking system, the radial diameter of the wheels, and the distance between the center of rotation and the lifted cargo. Crane lifting charts guide us through this latter variable. Those same charts account for angular changes and the addition of a jib.

Power Transmission Criteria

Hydraulic muscle provides lift power. The mechanical framework described above defines the structural competence of the vehicle, a feature that meshes with a large fluid reservoir and a dynamic pump. The quality of the non-compressible hydraulic oil provides yet another variable in our calculations but becomes inconsequential as long as a diligent hire company uses a planned maintenance program to ensure the hydraulic components are operating at peak efficiency.

What is Moment Rating?

Mobile crane power appraisals use a special formula to calculate the load capacity of a particular model. Variables and constants are reduced down to an absolute number when the moment rating is estimated. The calculation uses the load weight and the load radius (distance from the load to the rotating axis) as a means of comparing required load capacity against what’s available. Remember, this radius will vary as the segmented boom extends and retracts.

Load Weight vs. Load Capacity

It’s worth remembering at this point that all calculations are leveraged against a particular cargo, but something is amiss. The weight referenced in the moment rating calculation also has to incorporate the heft of the wire rope, all of the rigging, and any travel blocks.

When estimating mobile crane power, we identify major components and establish the load points on all moving and stationary parts. Next, engineering calculations consolidate available power and weigh this value against the power source at the other end of the power transmission chain. The formula uses overall weight, axial distance, and other dimensional variables to provide an intelligent evaluation of available crane truck power.

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