ST Bunn Compacts School Parking Lot with Varying Turning Speeds
BY Tom Kuennen
ST Bunn Construction Company Inc., Tuscaloosa, Alabama, just marked 80 years of business. However, the asphalt contractor and producer is anything but old-fashioned in its pursuit of new technology to improve pavements.
ST Bunn Construction has five asphalt plants within a 150-mile radius of Tuscaloosa. Numerous crews in west central Alabama place asphalt from these five plants using, among other equipment, two 10-foot Super 2003-3i and one 8-foot Super 1703-3i wheeled asphalt pavers from Vögele.
The company also has unique Hamm rollers, including two HD+120 VO tandem rollers, and an H13i VIO soil compactor incorporating both vibration and oscillation compaction in a single drum. In July 2018, ST Bunn Construction’s president, ST “Sonny” Bunn, Jr., acquired a new DV+70i VV-S roller. It features all-wheel steering with two smooth vibratory drums, but with a twist: both front and rear drums are split into halves, which can turn at different rates when negotiating tight curves or radii as seen in cul-de-sacs or parking lots.
As an added plus, the roller swaps steering via conventional articulated joint for all-wheel steering that permits precise movement on mats, including “crab” steering.
“We do a lot of jobs where we go around cul-de-sacs, or commercial parking lots and are rolling around islands. Turning the machine has a tendency to tear the mat,” Bunn said. “Normally, we would run a rubber tire roller on one of those jobs to close the mat back up.”
“I remember years ago, when rollers turned with the drums instead of an articulated joint, we didn’t have near the problems we have now with tearing of the mat. I started trying to find a new roller that turned with the drums instead of articulation.”
He tells the story of going to the Hamm factory in Germany and getting to see the DV+ roller there, and then seeing a DV+70i VV-S demonstration on a cul-de-sac a few months later. “Sure enough, it didn’t break the mat, or leave a roller mark,” Bunn said. “One of our senior operators was able to show the rest of the crew how it would perform in the field. We acquired the roller and use it nearly every day.”
Because the DV+ series turns via drums, rather than an articulated joint, it can meet some difficult compaction challenges. When the opportunity presents itself, the “crab” steering offset enables the machine to compact a wider area than the roller drums themselves. However, ST Bunn Construction crewmembers like the drum-steering for a different reason.
“Crab steering works for us when we are working right up against a stand-up curb, or curb and gutter,” Bunn said. “The operator can put the front drum right up against the curb and not worry about the back drum getting up on the curb.”
Front-and-back slat windows in the floor of the DV+ series rollers permit a clear view of the drums from the operator’s platform. “If he can see his drum, he can see if it’s picking up asphalt,” Bunn said.
“The floor windows allow our operators to see the drums, and in particular, whether the water system has stopped working,” said Guy Watkins, operations manager. “The split drum keeps the mix from tearing on tight curves, and the crab steering gives the operator better visibility while compacting a wider area than the roller itself, especially in getting rid of roller marks.”
ST Bunn Construction also uses oscillation compaction in its two Hamm HD+120 VO tandem asphalt rollers and Hamm H13i VIO soil compactor.