Hydraulics makes excavator a contortionsist

Excavators and other off-highway equipment generally make extensive use of hydraulics for multiple functions. Pumps and motors pair up in hydrostatic drives for propulsion; motors and rotary actuators produce rotational and pivoting motion; and cylinders provide articulation for booms, arms, and buckets; for steering; for boom extension; and more. But few excavators — if any — offer the impressive moves of the Spider R105 from Euromach SpA, Montichiari, Italy.Euromach’s Spider R105

Euromach’s Spider R105
Euromach’s Spider R105 excavator uses multiple axes of hydraulic power to extend its reach up, down, and sideways and also to travel over extremely uneven terrain.

Powered by a John Deere 4-cylinder, 140-hp engine, the R105 features a hydrostatic drive for propulsion, hydraulic steering, and multi-axis boom for digging, loading, or just about any other task. What makes the R105 stand out, though, is that its wheels are mounted to the ends of beams that can be deployed in multiple directions. This means the machine can work on uneven terrain — even steep slopes —without having to extend stabilizers.

However, the R105 does have stabilizers, which can be used to extend its reach, as shown in the inset photo. Furthermore, its main boom offers the articulated motion of an excavator and a telescoping action to give it the added reach of a telehandler.

Cool and efficient
Other hydraulic functions are not so obvious. High efficiency of the R105’s hydraulic system is accomplished with an electronically controlled load-sensing system. This system monitors operation of hydraulic components and closely matches pump output to work requirements. Reducing the power required of the hydraulic pumps saves fuel.

An additional boost to efficiency is provided by the machine’s hydraulic fan drive. The fan drive uses pressurized hydraulic fluid to drive a fixeddisplacement motor. The fan is a centrifugal load, so fan speed is a function of motor torque. Therefore, speed can be regulated by controlling pressure across the motor.

hydraulic fan drive
A hydraulic fan drive runs at variable speed to provide optimal cooling that saves fuel and reduces engine emissions by keeping engine temperature within a narrow range.

In addition to the hydraulic motor and electrohydraulic pressure-control valve, other important components of the hydraulic fan drive are electronic temperature sensors and an electronic control module. The module monitors ambient temperature, engine coolant temperature, and other parameters, then commands the pressure- control valve to a setting that drives the fan at optimum speed.

Conventional fan drives run the fan at the same speed as the engine. This can cause the fan to run faster than is necessary or allow the engine to run hot, either of which can rob fuel efficiency. A diesel engine operates at highest fuel efficiency and lowest rate of emissions within a narrow temperature range. So the hydraulic fan drive’s tight temperature control not only conserves fuel, but minimizes emissions as well.