Duck Walking in Scrapers Causes and Solutions

[MikePhua]

What Is Duck Walking and Why It Matters
Duck walking refers to the rhythmic bouncing or hopping motion that scrapers experience during loading or hauling, especially on uneven terrain or poorly prepared haul roads. This phenomenon not only reduces operator comfort but also affects load consistency, machine wear, and fuel efficiency. In severe cases, it can lead to structural damage or premature failure of suspension components.
The term is often used interchangeably with “hop” or “bounce,” particularly in regions like the Midwest, but the underlying mechanics remain the same: oscillations caused by uneven ground, improper loading technique, or reactive suspension behavior.
Primary Causes of Duck Walking
Several factors contribute to duck walking, often in combination:

• Uneven terrain or washboard surfaces
  
• Overly aggressive loading speed
  
• Improper apron height during cut
  
• Rear tires striking mounds of dirt repeatedly
  
• Hard-packed or slabby soil that breaks unevenly
  
• Excessive tire pressure or imbalance
  
• Lack of cushioning systems in the hitch or bowl
  

In sandy or overly dry conditions, duck walking tends to worsen due to poor traction and inconsistent soil breakup. Conversely, overly wet fill can also trigger bouncing as the tires sink and rebound unpredictably.
Operator Technique and Timing
Experienced scraper operators emphasize timing and throttle control as key to minimizing duck walking. Recommendations include:

• Enter the cut slowly and begin loading with only the front engine
  
• Ramp up speed after partial bowl fill to stabilize rear tires
  
• Avoid shallow, fast cuts that create slabby soil conditions
  
• Keep the apron low enough to control cut depth but not so low that it drags
  
• Use differential lock only when traction is compromised—not as a duck walk solution
  

One veteran operator noted that straddling the bumps—splitting the tracks—can break the cycle of bounce. If duck walking begins early in the cut, pulling out and restarting after the rear tires pass the initial mound can reset the rhythm.
Mechanical Solutions and Modifications
Beyond operator technique, mechanical interventions can help reduce duck walking:

• Cushion hitch systems use hydraulic accumulators to absorb shock between the tractor and scraper. However, they are ineffective in the cut or fill where the hitch is locked.
  
• Automatic ride control systems stabilize the bowl using hydraulic dampening, reducing bounce during haul.
  
• Skid pads welded behind the blade can help smooth the cut surface before the rear tires pass over it. These can be fixed or hydraulically actuated.
  
• Adjusting tire pressure can reduce bounce severity. Lower pressure increases ground contact and dampens rebound.
  

Some contractors retrofit their scrapers with adjustable skid shoes, allowing operators to fine-tune ground contact based on soil type and blade wear. Others use railroad iron drags ahead of the rear tires to flatten the cut surface.
Material Behavior and Soil Conditions
Certain soils are more prone to triggering duck walking:

• Sticky topsoil that breaks in slabs leaves voids for tires to fall into
  
• Hardpan or clay layers resist clean cutting and rebound unevenly
  
• Loose sand lacks cohesion, causing inconsistent traction
  

In final grading, maintaining a partial load in the bowl can help stabilize the machine. Though controversial, this technique adds weight to the rear tires, reducing bounce and improving control. For hourly jobs, partial loads during finish passes are often acceptable.
Anecdotes from the Field
In North Dakota, an operator running a Challenger tractor with a JD 1810E pan reported that duck walking was worst in sticky topsoil. By slowing entry speed and keeping the apron tight, he reduced bounce significantly. In Australia, a scraper hand recalled running a stiff hitch 627 and preferring it over the newer cushion hitches, despite the physical toll—he adapted by pacing himself and relying on well-prepared rills.
Another operator in Wyoming emphasized the importance of matching RPM to ground speed during dumping. If the rear tires hit the initial blob of dumped material unevenly, duck walking can begin immediately. Dumping downhill and keeping the lip low helps prevent this.
Preventive Measures and Best Practices
To minimize duck walking:

• Maintain consistent apron height during cut
  
• Avoid over-speeding into the cut or fill
  
• Use cushion systems appropriately—not in locked positions
  
• Split tracks when possible to avoid repeating bounce patterns
  
• Monitor tire pressure and balance regularly
  
• Consider installing skid pads or drag bars for surface smoothing
  

Training operators to recognize early signs of duck walking and respond quickly is essential. Once the bounce begins, it tends to amplify unless interrupted.
Conclusion
Duck walking in scrapers is a complex interaction between terrain, machine dynamics, and operator input. While no single solution fits all conditions, a combination of refined technique, mechanical upgrades, and soil awareness can dramatically reduce its occurrence. In the world of earthmoving, smooth motion isn’t just about comfort—it’s about control, efficiency, and protecting the machine from the ground it’s built to conquer.