The Quad 9 Push Cat: A Legacy of Power, Precision, and Earthmoving History

[MikePhua]

Introduction to the Quad 9 Push Cat Configuration
The term “Quad 9” refers to a tandem configuration of two Caterpillar D9 dozers, mechanically or hydraulically linked to operate as a single unit for pushing large scrapers or performing high-resistance earthmoving tasks. This setup was especially popular in the 1960s and 1970s during major infrastructure projects, where brute force and synchronized control were essential.
Terminology Clarification

• Push Cat: A dozer used to assist scrapers by pushing them during loading to reduce cycle time and increase productivity.
  
• Scraper: A self-loading earthmoving machine that cuts, lifts, and transports soil.
  
• Tandem Dozer: Two dozers coupled together to function as one, often with synchronized controls.
  
• DPF (Diesel Particulate Filter): A modern emissions control device absent in older machines, allowing for unrestricted exhaust flow and raw power.
  
• Idler Axle: A non-powered axle used to support track tension and guide movement.
  

Historical Deployment and Field Memories
The Quad 9s were prominently used in large-scale grading operations such as the construction of Interstate 82 between Yakima and Ellensburg, Washington, during the late 1960s. Operators and surveyors recall the sheer force and coordination required to manage these machines, often working in tandem with fleets of 651 and 660 scrapers.
One operator’s father, a grade setter on the I-82 project, drove a 1968 Datsun pickup over rugged canyon roads to reach job sites. The truck endured 60,000 miles in two years, a testament to the demanding terrain and the relentless pace of construction.
Field Anecdote: The Wymer Canyon Incident
A legendary story from the Fred G. Redmond Bridge construction involves a steer car operator hauling concrete beams through Wymer Canyon. The steer car ended up dangling above the river, with the tractor’s drive axles nearly airborne. Rescue required a crane to navigate a circuitous route through Vernita, Vantage, and Ellensburg. The incident left a visible patch in the canyon’s rock wall and a lasting impression on local crews.
Preservation and Sightings of Quad 9s
Though rare today, some Quad 9 sets remain in yards or private collections:

• A pair was spotted in Scarcella’s yard in Kent, Washington, appearing dormant but intact.
  
• Another set was seen near Fernley and Fallon, Nevada, parked alongside vintage 651 and 641 scrapers.
  
• Peterson Cat showcased a set of DD9s at the National ACMOC Show in Santa Margarita, California, pushing a Cat 660 scraper until an idler axle broke mid-demonstration.
  

These sightings evoke nostalgia and admiration for the engineering feats of the past.
Cultural Footnote: Mario Segale and the Italian Earthmoving Legacy
The conversation around Quad 9s often intersects with stories of Italian-American contractors like Segale, Ceccanti, and Scarcella—known for their spirited crews and deep roots in the industry. Interestingly, Mario Segale, a prominent contractor, inspired the name of Nintendo’s iconic character “Mario.” His legacy, like the machines he operated, continues to shape both cultural and industrial landscapes.
Best Practices and Operational Insights

• Synchronize throttle and steering inputs to prevent track misalignment
  
• Inspect coupling mechanisms regularly for stress fractures
  
• Use experienced operators with strong communication skills for tandem setups
  
• Maintain clear sightlines and radio contact during scraper pushes
  
• Monitor idler axles and track tension to prevent mid-operation failures
  

Conclusion
The Quad 9 push cat configuration represents a bygone era of raw mechanical power and collaborative earthmoving. From canyon rescues to national shows, these machines have carved both landscapes and memories. Though modern equipment may offer digital precision, the legacy of the Quad 9 lives on—in stories, steel, and the soil they once moved.