Basic Operation of the Kobelco RK70 Rough Terrain Crane

[MikePhua]

The RK70’s Role in Compact Lifting
The Kobelco RK70 is a compact rough terrain crane designed for lifting operations in confined or uneven environments. Developed by Kobelco Construction Machinery, a division of Kobe Steel founded in 1930, the RK series was introduced to meet the growing demand for mobile cranes that could navigate tight job sites while maintaining lifting precision. The RK70, with a lifting capacity of approximately 7 tons and a boom length of around 24 meters, became a popular choice for utility work, small-scale construction, and industrial maintenance.
Its compact footprint and four-wheel drive allow it to operate on gravel, dirt, and uneven surfaces, while outriggers provide stability during lifting. The RK70’s design emphasizes simplicity, durability, and operator visibility, making it suitable for both seasoned crane operators and those transitioning from other equipment types.
Cab Layout and Control Configuration
The RK70 typically features two single joysticks—one on each side of the operator seat—used to control boom elevation, extension, swing, and winch functions. Japanese labeling on older units can pose a challenge for non-Japanese speakers, but the layout follows standard crane ergonomics.
Left joystick functions often include:

• Boom up/down
  
• Boom extend/retract
  

Right joystick functions typically include:

• Swing left/right
  
• Hoist up/down (winch control)
  

Additional controls may include:

• Outrigger deployment levers
  
• Engine throttle dial
  
• Load moment indicator (LMI) display
  
• Emergency stop button
  
• Mode selector for boom or jib operation
  

Operators should familiarize themselves with the control panel layout and labeling before operation. If labels are in Japanese, consider applying translated stickers or using a reference chart.
Startup and Safety Sequence
Before operating the RK70:

• Perform a walkaround inspection: check tires, outriggers, hydraulic lines, and boom condition
  
• Verify fluid levels: engine oil, hydraulic fluid, coolant, and fuel
  
• Deploy outriggers fully and ensure ground contact with pads
  
• Start engine and allow warm-up for hydraulic pressure stabilization
  
• Engage crane mode via selector switch
  
• Confirm LMI system is active and calibrated
  
• Test all joystick functions without load
  

Safety systems on the RK70 may include overload alarms, boom angle sensors, and swing limiters. Operators should never bypass these systems, as they are critical for safe lifting.
Common Operational Challenges
New operators often report limited functionality—such as only being able to raise or lower the boom—while other functions remain inactive. This can result from:

• Crane mode not engaged
  
• Safety interlocks preventing operation
  
• Hydraulic selector valve not set correctly
  
• Joystick wiring faults or solenoid issues
  
• Language barrier with control labels
  

A technician in Cebu once encountered an RK70 that only allowed boom elevation. After inspecting the selector valve and confirming the crane mode was inactive, he resolved the issue by toggling the mode switch and resetting the LMI system. The machine then responded to all joystick inputs.
Maintenance and Troubleshooting Tips
To keep the RK70 in optimal condition:

• Grease boom and swing bearings weekly
  
• Replace hydraulic filters every 500 hours
  
• Inspect winch cable for fraying or kinks
  
• Check joystick resistance and recalibrate if needed
  
• Clean electrical connectors and apply dielectric grease
  
• Monitor LMI system for calibration drift
  

If functions are unresponsive:

• Test joystick voltage output
  
• Inspect solenoid valves for sticking
  
• Verify hydraulic pressure at control block
  
• Check fuse panel for blown circuits
  
• Consult wiring diagram for signal tracing
  

Training and Operator Development
Operating a crane requires more than mechanical skill—it demands spatial awareness, load calculation, and adherence to safety protocols. For RK70 operators:

• Study load charts and understand boom angle vs. capacity
  
• Practice with light loads before full lifting
  
• Use spotters for blind lifts or tight spaces
  
• Attend refresher courses on crane safety and signaling
  
• Keep a logbook of maintenance and operational hours
  

In Japan, Kobelco offers factory training for RK-series cranes, emphasizing safe operation, maintenance, and troubleshooting. International operators may benefit from third-party training or mentorship from experienced crane professionals.
Conclusion
The Kobelco RK70 is a capable and compact rough terrain crane that excels in tight job sites and light-to-medium lifting tasks. While its controls may seem unfamiliar at first—especially with Japanese labeling—its design follows logical crane operation principles. With proper setup, safety checks, and control understanding, the RK70 can be a reliable asset for contractors and industrial crews. As with all cranes, respect for load limits, attention to maintenance, and operator training are key to safe and efficient operation.