The role of rated operating capacity
While hydraulic power plays an important role, lifting capacity must also be considered when determining attachment compatibility. "For example, a backhoe attachment can have a considerable amount of weight, but does not require a large amount of hydraulic flow," says Zupancic. "In addition to making sure that the skid steer is compatible with the attachment flow, the customer also needs to be able to safely carry the attachment around the jobsite on all four wheels."
Rated operating capacity plays an even larger role with attachments designed for lifting. "For example, Bobcat manufactures pallet fork attachments for both small-frame and large-frame skid-steer loaders (up to 3,000-lb. rated operating capacity)," says Fitzgerald. "Obviously, the large-frame skid-steer loader with heavy-duty pallet fork can lift more than the small- or medium-frame skid-steer loaders."
But being able to lift the load is not the only consideration. "Rated operating capacity is not only critical for the skid-steer loader to remain safe and stable while lifting and carrying the attachment, but also to provide adequate down pressure on attachments like cold planers, trenchers, tillers, etc.," says Hughes.
The rated operating capacity can often be slightly increased by using an optional factory counterweight package. "For customers at the upper end of the rated operating capacity, one model counterweight can add an additional 150 lbs. of capacity," says Moore, discussing Gehl's skid-steer models. "In addition, it serves as a bumper and hitch. The counterweight on our two larger E Series loaders increases the rated operating capacities by 300 lbs."
Similarly, Bobcat offers factory-approved counterweight packages through its dealers. "Loader owners can add counterweights — available from their dealership — to the machine for an increase in the loader's rated operating capacity," says Fitzgerald. "Even so, the loader owner should still closely follow the manufacturer's recommended limits for specific attachments and carriers."
Attaching weights to the front of the machine can help with the performance of certain attachments. "As long as the counter balance is within the recommended limits of the manufacturer, you can generally put as much weight on the front of the machine as needed because the limiting factors will be the hydraulic system breakout forces and the tipping load of the machine," says Zupancic. "Constant heavier loads will accelerate wear over the life of the machine. For example, constantly lifting 4,000 lbs. versus lifting 100 lbs. will increase wear on the pivot points of the boom linkage over time."
Wheelbase further impacts capacity
The wheelbase also affects the rated operating capacity. "For example, Bobcat has three wheelbase options to choose from," says Fitzgerald. "The small-frame loaders' wheelbase is approximately 36 inches; the medium-frame loaders are 40 inches; while the large-frame loaders are 48 inches. The large-frame skid-steer loaders' wheelbase allows for higher tipping loads and rated operating capacities."
In addition, the extended wheelbases enhance stability. "By extending the wheelbase on New Holland skid steers, we can better distribute the weight over a desired footprint and use the laws of physics to our advantage," says DeHoyos. This allows the skid steers to lift more with less vehicle weight. "The wider wheelbase gives the additional benefit of stability and gives the skid-steer operator more confidence."
Of course, there is more to rated operating capacity than the stance of the machine. "Extended wheelbases contribute to additional lift capacity, but there are other factors that also contribute," says Zupancic. "For example, total machine weight and the geometry of the boom design can also contribute to increased lifting capacities."