Restoring the Swivel Post on a Warner Swasey Hopco 550 Excavator

[MikePhua]

The Warner Swasey Hopco 550 and Its Mechanical Legacy
The Warner Swasey Hopco 550 excavator is a relic of American industrial engineering, built during an era when hydraulic systems were robust, mechanical linkages were overbuilt, and operator intuition mattered more than electronics. Warner & Swasey, originally known for precision instruments and turret lathes, ventured into heavy equipment through Hopco, producing a limited run of excavators that emphasized durability and simplicity. Though never mass-produced like Caterpillar or Komatsu machines, the 550 earned a cult following among operators who appreciated its raw mechanical strength.
The 550 features a house swivel post—a central rotating column that allows the upper structure to pivot independently of the undercarriage. This component is critical for trenching, loading, and maneuvering in confined spaces. When neglected, especially after years of inactivity, the swivel post can seize due to corrosion, lack of lubrication, and environmental exposure.
Diagnosing a Seized Swivel Post After Long-Term Storage
After sitting idle for four years, a 550 excavator was restarted and immediately encountered a locked swivel post. The machine rotated once, snapping off air lines in the process, and then refused to move further. Despite liberal application of penetrating oil (Kroil), the post remained immobile.
Terminology:

• Swivel post: The vertical shaft that enables the upper structure of an excavator to rotate
  
• Air brake adapter: A pneumatic interface used to lock or control rotation in some older machines
  
• Kroil: A penetrating oil known for its ability to loosen rusted or seized components
  

Moisture in compressed air systems is a known culprit in corrosion. Without an air dryer, condensation settles in low points like the swivel post base, initiating rust that can weld surfaces together over time. In this case, the corrosion was severe enough to immobilize the entire house rotation.
Manual Disassembly and Restoration Strategy
The operator undertook a full teardown of the swivel post assembly. This involved:

• Removing the house brake mechanism
  
• Prying up the air adapter housing
  
• Manually freeing the swivel post using leverage and persistence
  
• Reassembling the unit with fresh grease—eight tubes in total
  

This hands-on approach restored rotation and prevented future seizure. The operator committed to regular greasing, recognizing that neglect had nearly condemned the machine to the scrap heap.
Preventative recommendations:

• Grease swivel post monthly during active use
  
• Install an air dryer or moisture trap in pneumatic systems
  
• Inspect seals and gaskets annually for signs of wear
  
• Rotate the house periodically during long-term storage to prevent static corrosion
  

Reviving a Neglected Excavator with Multiple Failures
Beyond the swivel post, the 550 faced a litany of mechanical issues:

• Engine running on two cylinders
  
• Broken track and drive sprocket
  
• Air cleaner clogged with debris
  
• Shattered cab windows
  

Despite these setbacks, the machine was gradually restored. The operator replaced filters, repaired the track, and even used another dozer to reposition the excavator after it slid off a hillside—narrowly avoiding injury from falling trees. The engine maintained oil pressure throughout, a testament to its resilience.
In one dramatic moment, the track came off again, but was pushed back on using a second machine. The operator continued trenching operations, reaching 75 yards before discovering a fuel pressure issue—only 10 psi instead of the expected 50. Diagnosis revealed full flow to the pump, suggesting internal bypassing or wear in the gear-driven fuel pump.
Hydraulic Line Failure and Field Repairs
While trenching through hard clay and rock, a hydraulic line burst, halting progress. With the nearest parts store 120 miles away, the operator opted to go fishing and test a metal detector while waiting for Monday repairs. This improvisational spirit reflects the reality of rural equipment ownership—where downtime is inevitable, and patience is part of the toolkit.
Repair tips:

• Carry spare hydraulic hoses and fittings for field emergencies
  
• Use protective sleeves to reduce abrasion on exposed lines
  
• Pressure test new lines before full operation
  
• Document hose lengths and fitting types for future replacements
  

Fuel System Troubleshooting and Detroit Diesel Insights
The 550 is powered by a Detroit Diesel 6-71 engine, known for its simplicity and reliability. However, the gear-driven fuel pump can wear over time, reducing pressure and causing performance issues. Removal of the pump requires specialized tools, including a curved double box-end wrench due to tight clearances.
Fuel system diagnostics:

• Measure pressure at the fuel rail and return line
  
• Inspect filters and check for blockages
  
• Verify pump output against manufacturer specs
  
• Replace worn pumps with OEM or remanufactured units
  

One technician noted that low pressure on the return line often correlates with pump wear, especially in older Detroits. Full flow from tank to filter does not guarantee proper pressure at the injectors.
Conclusion
Restoring the swivel post and broader functionality of a Warner Swasey Hopco 550 excavator is a testament to mechanical perseverance. Through manual disassembly, field improvisation, and deep respect for old iron, the operator brought a forgotten machine back to life. In the world of vintage equipment, success isn’t measured by speed—it’s measured by grit, grease, and the will to dig one more trench.