Can the Rosco Roll-Pac Be Made to Vibrate

[MikePhua]

Origins of the Rosco Roll-Pac
The Rosco Roll-Pac is a compact ride-on roller developed by Rosco Manufacturing, a division of LeeBoy, Inc., a company with deep roots in road construction equipment dating back to the 1960s. Rosco began as a manufacturer of asphalt distributors and gradually expanded into compaction and maintenance machinery. The Roll-Pac was introduced as a lightweight, maneuverable roller designed for patchwork, trench compaction, and small-scale paving operations. Its compact footprint and split-drum configuration made it a popular choice for municipalities and contractors working in confined spaces.
While exact production numbers are not publicly available, industry estimates suggest that several thousand units were sold across North America during the 1990s and early 2000s. The machine’s simplicity and rugged build earned it a reputation for reliability, though its lack of advanced features—such as integrated vibration—has prompted many users to explore retrofitting options.
Understanding the Drum Configuration
The Roll-Pac features a unique drum layout: two split front drums and a single rear drum. Split drums are designed to reduce surface tearing during turns, especially on fresh asphalt. This configuration allows for differential rotation between the left and right halves of the drum, minimizing scuffing and improving finish quality. The rear drum, typically wider and solid, provides the primary compaction force.
However, unlike modern vibratory rollers, the Roll-Pac relies solely on static weight for compaction. This limits its effectiveness on granular soils and thicker asphalt layers, where vibratory energy is essential to achieve density targets.
What Is Vibratory Compaction
Vibratory compaction involves the use of eccentric weights mounted on shafts inside the roller drum. As these weights rotate, they generate vertical or horizontal vibrations that transmit energy into the material being compacted. This process reduces air voids, increases density, and improves load-bearing capacity.
Key parameters in vibratory systems include:

• Amplitude: The maximum displacement of the drum during vibration, typically measured in millimeters.
  
• Frequency: The number of vibrations per minute, often ranging from 2,500 to 4,000 VPM (vibrations per minute).
  
• Centrifugal Force: The force generated by the rotating eccentric mass, expressed in kilonewtons (kN).
  

Modern vibratory rollers allow operators to adjust these parameters based on material type and layer thickness. Unfortunately, the Roll-Pac lacks any built-in vibration mechanism, which raises the question: can it be retrofitted?
Retrofitting Vibration Systems
Retrofitting a vibratory system into a static roller is technically feasible but economically and mechanically challenging. It requires:

• Installing eccentric shafts and bearings inside the drum
  
• Reinforcing the drum shell to withstand dynamic loads
  
• Adding hydraulic or electric drive systems to power the eccentric weights
  
• Integrating control systems for vibration frequency and amplitude
  

In the case of the Roll-Pac, its compact design and split drum configuration complicate this process. The split drums would require independent vibration systems, and the frame may not be engineered to absorb the resulting stresses. Additionally, the cost of retrofitting could exceed the value of the machine itself.
A more practical alternative is to use the Roll-Pac for finish rolling or light-duty compaction, and pair it with a vibratory plate compactor or trench roller for deeper layers. This hybrid approach is common in utility work and patching operations.
Does Vibration Make a Difference
Yes—vibration significantly enhances compaction efficiency. Studies by the Federal Highway Administration show that vibratory rollers can achieve up to 20% higher density compared to static rollers in granular soils. In asphalt applications, vibration helps eliminate surface cracking and improves long-term durability.
A real-world example comes from a municipal paving crew in Ohio that replaced their aging static rollers with vibratory units. Within weeks, they reported fewer callbacks for pothole repairs and smoother transitions between patches. The investment paid off in reduced labor costs and improved road quality.
Operational Tips for the Roll-Pac
Even without vibration, the Roll-Pac can deliver solid results if used correctly. Here are some best practices:

• Use multiple passes with overlapping coverage to increase compaction
  
• Operate at slower speeds to allow more time for material consolidation
  
• Apply water to the drum surface to prevent asphalt pickup
  
• Avoid sharp turns on fresh material to minimize surface tearing
  

Routine maintenance is also critical. Check drum bearings, hydraulic lines, and steering linkages regularly. Grease fittings should be serviced every 10 hours of operation, and drum surfaces kept clean to ensure uniform contact.
Legacy and Longevity
Despite its limitations, the Rosco Roll-Pac remains a respected tool in the compaction world. Its simplicity, ease of transport, and low operating costs make it ideal for small contractors and municipalities. While it may not match the performance of modern vibratory rollers, it continues to serve as a reliable workhorse in niche applications.
In recent years, some enthusiasts have begun restoring vintage Roll-Pacs, swapping engines, repainting frames, and even experimenting with vibration retrofits. One such project in Alberta involved installing a hydraulic motor and eccentric shaft into the rear drum, yielding modest vibration output. Though not commercially viable, it showcased the ingenuity of the equipment restoration community.
Conclusion
The Rosco Roll-Pac cannot vibrate in its original form, and retrofitting is rarely practical. However, with proper technique and complementary equipment, it remains a valuable asset for light-duty compaction. Its legacy lies not in high-tech features but in dependable performance and mechanical simplicity—a testament to an era when machines were built to last.