Wheel loaders are four-wheel-drive earthmoving machines used primarily as loading equipment to load loose materials with a front-mounted bucket.
A lift-arm assembly raises and lowers the bucket, and a bellcrank in the assembly opens and closes the bucket. Most wheel loader manufacturers classify their product lineup into four categories with these approximate power and bucket-capacity specifications: compact (40-100 horsepower, 1.0-2.5 cubic yards); small (115-180 horsepower, 2.5-6.5 cubic yards); medium (230-400 horsepower, 3.75-15.0 cubic yards); and large (with horsepower ratings up to 1,800 or more and capacities in excess of 30 cubic yards).
The largest units typically are used in specific applications, such as mining. As models decrease in size, they tend to be more utilitarian, many of them equipped with a hydraulic coupler that can accept a range of attachments, such as material-handling forks, dozer/snow blades, grapples, specialty buckets (such as side-dumps), and brooms.
The power train of most models uses a fuel-efficient diesel engine that drives through a torque converter into a multi-speed power-shift transmission that might use a transfer case to split output power between the front and rear planetary-reduction axles. A more recent design concept uses a combination of mechanical drive and hydrostatic drive to propel the machine.
A few models are now using electricity to propel the machine and to power hydraulic systems, ranging from compact machines that are completely powered via batteries, to larger models that use a small diesel engine to drive a motor/generator that supplies power to electric drive motors located at the transmission or at the wheel hubs.
Technical advancements include
- Engines are durable, fuel-efficient, and produce few exhaust emissions
- Transmissions now use electronic control, allowing them to precisely match engine output with speed and load demands
- Hydraulic systems typically use highly efficient variable-displacement pumps, and some systems have regeneration circuits that can transfer hydraulic fluid with the cylinders
- Operator’s environment has an automotive-like design, featuring low-effort, electro-hydraulic controls; climate-controlled, pressurized cabins; choice of seat designs; and in some instances, safety systems such as proximity-warning.