In the past, most variable reach forklifts were built with an overall height of more than 100 inches. But as jobsites become more space restricted, engineers are finding that telescopic handlers need to be more versatile, especially for lifting inside buildings.
The ability to fit under an 8-foot overhang, the common height of a typical doorway, has become the norm for telescopic handlers. Therefore, most manufacturers now offer low-profile models. Included, is the choice between a low-boom pivot and a high-boom pivot, which both feature design advantages and disadvantages.
Low-boom pivot A primary asset of the low-boom pivot design is good visibility when the forks or attachments are on the ground. The design also has a narrow frame, allowing for easier access to small spaces and a tighter turning radius.
However, the low-boom pivot requires a side-mounted engine, which makes service points on the backside of the engine difficult to access. Side-mounted engines also require an angle drive, resulting in a loss of power and a poor power-to-weight ratio.
With the heaviest component, the engine, on one side of the frame, additional weight is distributed to other areas of the machine to pass the American Society of Mechanical Engineers' B56.6 stability test. This adds to the poor power-to-weight ratio.
When carrying loads 2 to 6 feet off the ground, visibility is reduced to the right side because the boom crosses the side of the operator compartment. Lower-boom pivot designs also offer less forward reach at maximum lift height.
Ideal applications for this type of machine include jobs that work close to the ground and often require ground-engaging attachments such as sweepers or buckets.
High-boom pivot An overall height of less than 8 feet gives the high-boom pivot design many of the same worksite advantages as the low-boom model. However, when raising the forks 24 inches or higher off the ground with the high-boom style machine, the operator has full visibility to the right side, a benefit not found on the low-boom pivot designs.
Its center-mounted engine maximizes the engine's weight, which is low in the center of the frame between the axles. This provides many significant advantages, including a better power-to-weight ratio, easy-to-access service points and a direct drive to the transmission.
The high-boom pivot design also offers a greater forward reach at maximum lift height. With the boom in the level position, the bottom of the boom comes across the top of the operator station, providing a direct line of sight to the work area underneath.
Its better power-to-weight ratio provides longer life to components and better overall performance. The lower weight of the design means efficient fuel consumption and lower trucking costs. Higher boom pivots are rigid and offer little lateral movement of the boom when carrying loads over rough terrain.
With the pros and cons of both types of machines, many would say that the jury is still out regarding low-boom pivot versus high-boom pivot machines for the North American rental market. However, the low-profile high-boom pivot design, with its 95-inch overall height, is superior for safe handling of materials and an excellent power-to-weight ratio. On the other hand, the low profile, low-boom pivot design offers excellent agility around a construction site.
Knowing what is required for the job is the most important step to picking the best boom. Then you be the judge.