But how do manufacturers assign crane ratings? And why are articulating and telescopic cranes rated differently?

What essentially differentiates a telescopic crane from an articulating crane — other than the obvious straight boom versus knuckleboom — is reach capability and payload transportation ability.

A truck-mounted articulating crane is designed to place payload on the truck bed, haul it to the job site, and then place the payload where it ultimately needs to go. That’s not the case with telescopic cranes, which are designed to be stored over the truck bed, leaving little room for product transportation. Because a telescopic crane has a winch and an articulating crane has a hook on the end of the boom, this not only affects their reach and payload capacities, but also how the cranes are rated.

Articulating cranes don’t usually have the vertical reach capabilities that telescopic cranes do, so they’re typically used on job sites where horizontal reach is the major concern. This is one reason why manufacturers rate articulating cranes by measuring their maximum lift capacity when the boom is horizontal with all extensions retracted. For example, an articulating crane rated at 90,000 foot-pounds, means the crane can lift 6,000 pounds when its boom is extended to 15 feet. In order to have a uniform rating, all articulating crane manufacturers have agreed to use this formula. Load charts show the crane’s capacity at horizontal reaches, while load ranges depict its vertical capacities.

Telescopic cranes are rated a little differently. Instead of their lift capacity being measured at a horizontal reach, telescopic cranes receive their maximum capacity ratings based on how much they can lift with the boom extensions retracted and the lower boom raised to maximum elevation. The radius is then measured from the winch line to the center of rotation, usually about 5 feet.

With telescopic crane ratings, the correlation between feet and lift capacity is depicted on their lift charts by showing the booms at different angles and extensions. The rated capacity is shown at the intersection of the vertical load radius line and the horizontal line showing boom tip position. However, as the boom lowers, the specs will show a drastic drop in the telescopic crane’s lift capacity.

While articulating crane ratings are measured in foot-pounds, most manufacturers state telescopic crane ratings in tons. However, we’re one manufacturer of both articulating and telescopic cranes who doesn’t. We rate our IMT telescopic cranes the same way we rate our articulating cranes — in the foot-pound capacity style.

Written By: Jim Darr, Product Specialist for Material-Handling Systems

Iowa Mold Tooling Co., Inc. (IMT)

Garner, Iowa