Komatsu PC75 Bucket Collision with Cab Causes and Corrective Measures

[MikePhua]

The PC75 and Its Compact Excavator Design
The Komatsu PC75 is a mid-sized compact excavator designed for urban construction, utility trenching, and site preparation. With an operating weight around 16,000 lbs and a dig depth exceeding 15 feet, the PC75 balances power and maneuverability. Its zero tail swing and tight turning radius make it ideal for confined spaces, but its boom and bucket geometry must be carefully calibrated to avoid interference with the cab structure.
Komatsu, founded in 1921 in Japan, has long been a leader in hydraulic excavator innovation. The PC75 series was part of its push into compact machines with full-size capabilities. While the machine’s hydraulic system and structural layout are robust, improper bucket selection or linkage wear can lead to unintended contact between the bucket and cab—posing safety risks and operational inefficiencies.
Terminology Clarification

• Boom: The primary lifting arm of the excavator, connected to the stick and bucket.
  
• Stick (or dipper arm): The secondary arm that extends from the boom to the bucket.
  
• Linkage geometry: The arrangement and pivot points of the boom, stick, and bucket that determine movement range.
  
• Pin-on bucket: A bucket attached directly to the stick via pins, without a quick coupler.
  

Common Causes of Bucket-to-Cab Contact
When a bucket strikes the cab during operation, several factors may be at play:

• Incorrect bucket size or shape exceeding design clearance
  
• Worn bushings or pins causing excessive play in the linkage
  
• Aftermarket bucket with improper curl radius
  
• Boom or stick cylinder drift due to internal leakage
  
• Operator error during tight maneuvering or backdragging
  

A contractor in Alberta experienced cab contact while trenching near a foundation. The issue was traced to a non-OEM bucket with a deeper curl profile, which exceeded the machine’s safe retraction envelope.
Inspection and Diagnostic Strategy
To identify the root cause:

• Measure bucket dimensions and compare with OEM specifications
  
• Inspect stick and boom pivot points for wear or elongation
  
• Check hydraulic cylinder seals for drift or delayed response
  
• Observe bucket movement during full curl and retraction
  
• Review operator technique and attachment history
  

Recommended tools:

• Calipers and measuring tape for bucket geometry
  
• Flashlight and pry bar for bushing inspection
  
• Hydraulic pressure gauge for cylinder testing
  
• OEM service manual for clearance diagrams
  

A technician in Georgia used a borescope to inspect internal wear in the stick cylinder. After replacing the seals and recalibrating the linkage, the bucket no longer contacted the cab during full curl.
Solutions and Preventive Measures
To correct and prevent bucket-to-cab interference:

• Replace non-OEM bucket with factory-approved model
  
• Install wear shims or replace bushings at pivot points
  
• Adjust hydraulic cylinder stroke limits if applicable
  
• Add cab guards or deflectors for temporary protection
  
• Train operators to avoid full curl near cab during backfill or cleanup
  

Additional recommendations:

• Use quick couplers with built-in geometry control
  
• Avoid oversized buckets that exceed machine’s breakout force
  
• Inspect linkage monthly for signs of wear or misalignment
  
• Document attachment changes and verify compatibility before use
  

A fleet manager in British Columbia standardized bucket inventory across his PC75 units, ensuring all attachments met factory clearance specs. This reduced cab damage incidents and improved operator confidence.
Operator Technique and Safety Awareness
Even with proper equipment, operator habits play a critical role:

• Avoid curling bucket fully when close to cab or boom
  
• Use float mode when backdragging to reduce hydraulic force
  
• Maintain visual awareness of bucket position during tight maneuvers
  
• Report any unusual movement or contact immediately
  

Operator tips:

• Practice slow, deliberate movements during final grading
  
• Use mirrors and cameras if available to monitor blind spots
  
• Keep cab windows clean for maximum visibility
  
• Avoid using bucket as a pry tool near cab structure
  

A crew in Texas implemented a training module focused on attachment awareness and hydraulic control finesse. The result was a 60% reduction in minor contact incidents over one season.
Conclusion
Bucket-to-cab contact on the Komatsu PC75 is a preventable issue rooted in geometry, wear, and technique. With proper inspection, compatible attachments, and disciplined operation, the machine can perform safely and efficiently across a wide range of tasks. Whether trenching, grading, or clearing, maintaining clearance integrity is essential to protecting both equipment and operator. In compact excavation, precision is not optional—it’s the foundation of productivity.