What Is Range of Motion?
by Sean Larin - Product Manager On Nov 14, 2019, 03:00 AM
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Telescopic and articulating boom lifts rotate, elevate and extend multiple boom sections to help operators access difficult to reach worksites. The work area that each boom lift model can access is determined by the combination of its vertical height and horizontal outreach capabilities — commonly referred to as the boom’s range of motion, or working envelope.
Range of motion charts are available for each boom lift model in the Operator’s Manual stored on the machine and its specification sheet. These charts feature a 2-D picture of the arc-like area in which each boom can reach, laid over a graph that makes it easy to determine the unit’s access capabilities. The range of motion chart is an extremely valuable tool for selecting the best mobile elevating work platform (MEWP) for a jobsite application.
Model numbers often reflect the maximum vertical reach capabilities of a boom lift’s platform or deck. For example, The Genie® S®-60 XC™ model name designates a 60-ft (18.28 m) telescopic boom. As a general rule of thumb, outreach for a telescopic boom was traditionally around 9 ft (2.74 m) less than the platform height. However, it is vital that operators always reference the model’s range of motion chart and Operator’s Manual before starting work to help ensure they are working safely.
Many boom lifts that share the same basic specification, such as platform height or horizontal outreach, can show significant differences in their range of motion. These have the potential to impact an operator’s productivity or ability to reach a specific work surface.
Although many boom lifts have a smooth arc shape range of motion, occasionally there is a “saw-tooth” shaped work envelope. Here, the operator may have to retract or reposition the boom to perform a successive task when moving along the outer edge of the working envelope. Another feature that can be found in a range of motion chart is whether a machine can perform below ground reach. This is important for certain applications such as bridge inspections, surface mining and general ground grading.
Increasingly, a range of motion chart may also provide additional guidelines for dual capacity work envelopes. Dual capacity boom lifts, such as the Genie Xtra Capacity™ boom series, offer both unrestricted and restricted platform weight capacity ratings dependent on the boom lift’s extension and position. Unrestricted platform capacity is the term used by most manufacturers to specify one platform weight capacity applicable for all areas within the machine’s range of motion. Restricted platform capacity is used by some manufacturers to specify platform weight restrictions for certain segments within the machine’s range of motion, most often at the furthest outreach area of a booms working envelope.
Range of motion charts for each model are available in the Operator’s Manual and specification sheets can often be viewed online at the manufacturer’s website. For Genie boom lifts, visit genielift.com/en-gb.