With margin pressures greater than ever, haulers learn what transfer trailer configurations work best for their specific operations.
Nobody knows more than a manager of an MSW hauling operation what a challenge it is to maximize operational profitability. The cost of fuel is a barrier to profitability that has emerged with an increased impact during the past couple of years. Haulers who run transfer trailers between transfer stations and landfills have always been concerned about making the most of payload capacities.
The design of the trailer and the materials used in the sidewalls and floor have a major bearing on the trade-off that haulers sometimes face between a trailer’s payload capacity and its operational life. The trailer’s ability to withstand the inevitable abuse from front-end loader buckets, as well as unloading efficiency, earns plenty of scrutiny from margin-focused managers.
Several managers who spoke with MSW Management shared the lessons learned in transfer trailer specifying that only years of experience can impart. A couple have even helped trailer manufacturers to design a more durable, safer product—and who would know better how to achieve that than the individuals who see the trailers in action every day.
Smooth Versus Sheet-and-Post Sidewalls
There are varying schools of thought in regard to sidewall design and material. One manager has switched to a smooth sidewall due to some benefits that its design provides. Two others prefer the conventional sheet-and-post sidewall because they believe that it provides superior durability that more than compensates for any disadvantages to the design.
Genesis Smooth Walls from East Manufacturing are the choice of KRD Trucking, Linwood, Ill., and owner Ken Drenth. The company has about 600 trailers, including about 570 tipper trailers and operates in 11 states. Drenth reports that his company has specified the Genesis sidewalls for the past five years.
The concept behind the design of the Genesis sidewalls is comparable wall durability to the conventional sheet-and-post design in which the posts are located on the walls’ exterior, but with two advantages: better aerodynamics and thus fuel economy, and reduced wall thickness that allows a higher payload volume in some cases. The walls are 2 inches thick, reinforced with internal ribs spaced every 3 inches, and continuously welded together vertically. A double-wall design protects the outer walls against dents. Three-inch spacing on the ribs reportedly provides eight times more support than external posts at 25-inch spacings. Cross-members and floor plates interlock into the bottom rub rail to form a pocket and the sidewall panels interlock into this pocket to strengthen a key stress point.
Another design element is incorporated to provide durability to the part of the sidewalls that receives the most abuse during loading. The walls are designed with a top rail that is flush with the outside of the wall but that overhangs the inside edge for added strength and protection against loading damage.
“We had always run aluminum with a sheet-and-post design,” says Drenth. “We went to the smooth design primarily for fuel economy and you can get more capacity with a smooth side trailer—those are the two key reasons that we buy them. There wasn’t really a weight savings; the main force was the fuel economy and the larger inside dimensions.”
Drenth also claims that the Genesis wall-rail pocket provides a benefit in sidewall rigidity. “The other key factor with these Genesis sidewalls is we don’t need to run a center bar in the trailer to keep the sides from spreading, which is very helpful,” he says. “It’s one less item the loader can hit and damage. The vertical panels are able to maintain the integrity of the trailer without the sidewalls spreading.”
Even though he has not quantified the benefits from using the smooth walls in terms of fuel savings in dollars or added revenue from additional payload, Drenth says that the company has identified a benefit in terms of fuel economy. “We looked at the difference in the fuel economy vs. the sheet and post we initially looked at purchasing and we looked at a couple of tenths of a mile in fuel economy and we’ve seen it prove itself.” This benefit is not insignificant, considering the skyrocketing price of fuel. “A couple of years ago, I know we were in the $2 [per gallon] area and now we’re seeing $4,” he notes.
Although it’s too early to tell, Drenth expects that the smooth walls will give his trailers the same lifespan as the sheet-and-post design used to. “We’ve got some sheet-and-post trailers that are 10 to 12 years old and they’re still going, so I guess time will tell,” he says. “But we’re on track as far as durability; I think we’re going to be in that same timeframe. As of yet, I don’t see them lasting longer than the sheet and post, but we’ll see.”
But Gary Gray, president of Gary W. Gray Trucking Inc., Delaware, N.J., still thinks that the sheet-and-post sidewalls on his trailers from Mac Trailer Manufacturing provide the best durability. His company primarily hauls refuse throughout northern New Jersey, Pennsylvania and Connecticut in a fleet of about 300 transfer trailers that is evenly split between tipper and moving-floor units.
“It’s a little more rugged,” Gray says of the sheet-and-post sidewall. Durability is paramount for Gray, who also exclusively specifies rugged Reyco 21B spring suspensions on his trailers. “It just takes the abuse of pounding from loads in it a little better. With the smooth sidewalls, I think there is some fuel saving advantage in them, but we need the durability and [the sheet-and-post sidewalls] are a little lighter. We went both ways for a while there, but now we’re back at buying nothing but sheet and post. [The smooth wall] is not lighter weight—it’s a little heavier—but it is more aerodynamic and it gives you a little more cubic feet of space in the trailer because it’s thinner. You can pick up 4 to 7 more cubic yards, depending on the length of the trailer, with a smooth wall, so there’s an advantage there if you’re hauling a lighter product.”
According to Gray, the most common source of abuse of a transfer trailer is front-end loaders. “It’s loaders, and the material that they might be trying to push down in there—construction demo or what have you,” he says. “And then the machines and operators, some of these places are pretty rough.”
C&W Trucking in Winter Garden, FL, has used both types of sidewalls on its Mac Trailer transfer trailers and most recently has stuck with sheet and post. Kevin Creeden, vice president of operations, reports that the company began to diversify from hauling rock and sand to refuse hauling a few years ago and operates about 25 tipper trailers and 60 moving-floor units. C&W mainly hauls refuse in central Florida and has begun to specify sheet-and-post sidewalls for maximum durability.
“We’re still on a learning curve because the tipper trailers are relatively new to us,” Creeden says. “The youngest one we’ve got is three years old. The live-floor trailers, we’ve been using those for a long time, whether it’s for potting soil or wood product applications. In the last three to five years we’ve gotten kind of heavily into trash hauling and C&D. We’ve been running the tippers for about three years; the walking floors, we’ve been running for at least five years, maybe closer to six. We’ve had live floors for probably 10 or 12 years, but they’ve been hauling wood products, mulch, potting soil, not nearly as abrasive and abusive as some of the trash hauling is.” Because of the relative abrasiveness of some refuse material, Creeden and C&W have opted for the ruggedness of sheet-and-post sidewalls.
Trade-Off in Moving Floors
Where the use of tipping trailers is not feasible due to space and equipment considerations, moving floors provide efficient unloading capability. The material used—steel or aluminum—is subject to a specification decision driven by a similar trade-off that exists for the sidewalls: durability vs. payload capacity.
Gray’s moving floor–equipped trucks utilize the Keith Walking Floor, which has aluminum slats, which provide weight savings and are durable. “We use 100% aluminum,” says Gray. “The aluminum is a lot lighter. The steel is great if you’ve got really rugged material—aggregates or something—that’s going to bang up the floor. But for normal use, the aluminum slats, the high impact floors—that’s what we use—they’re more or less bulletproof.”
The Walking Floor operates in a four-stage process. Floor slats or planks slide underneath the load in groups of three, one group at a time. In the fourth and final stage, all of the grouped slats/planks move together toward the discharge end of the trailer, pulling the load along in that section of the floor. Various slat designs are available, including the high-rib Impact slats that Gray uses.
“We’ve found the Keith to be very, very good and wanted to standardize on one thing,” Gray points out. “When you’ve got 300 trailers running around, you want everything to be the same. We’ve got our own maintenance shop here.”
Creeden and C&W Trucking are using moving-floor trailers for refuse as well as for soil and mulch. “There are some hauls that are tipper applications, just a short shuttle where we can use the tippers,” he says. “The longer hauls where we have a backhaul are where we get into using the walking floors.”
C&W’s central Florida market is not characterized by many trailer tippers, Creeden notes. In fact, he says he knows of only two landfills equipped with tippers in the entire state. “Some of it also depends on the customer—where we’re picking up and where we’re going to determines whether we use a walking floor or a tipper,” he says.
Having diversified from hauling dirt and mulch to refuse in its moving-floor trailers, C&W has sought to make the floors more rugged. “We’ve changed a little bit on the floor; we’ve gone to a little heavier trash floor compared to [Mac Trailer’s] normal trash floor,” says Creeden, who says the company has begun specifying aluminum floors over steel floors due to weight considerations. “We were just looking at the durability of our floors because floors wear out and, depending on the application, you’re looking at putting a new floor in a trailer sometimes every two, two and a half years. We were looking at the expense of that. We’re trying to come up with a time frame on trailers—how long we keep them before we trade them in vs. repairing them.
From Creeden’s standpoint, payload capacity considerations won out in regard to the choice of flooring material. “We get paid by the net weight we haul,” he says. “There’s a trade-off there—we haven’t seen where [steel] is feasible for what we do. With more expense and a heavier floor, we haven’t seen it as enough of a trade-off to go that way yet.”
The aluminum floor slats have proven to be rugged enough for the refuse that C&W hauls, Creeden adds. “There are normal wear issues because of what we’re hauling,” he says. “Because of how they load the trailer sometimes, they’ll mess something up before it gets worn out; they’ll drop a big boulder in there that really dings a slat. But the floors are usually pretty forgiving. I don’t think we’ve ever had a situation yet where a slat has been bent so badly that it didn’t work at all.”
The process of determining a trailer’s lifespan is still underway at C&W. Part of the reason why this is a complicated process is that some trailers are used to haul refuse first, and then used to backhaul a less abrasive material, making apples-to-apples comparisons among trailers difficult. “Sometimes we’re swapping trailers among certain drivers because maybe they’re hauling trash today, but they’ll be hauling something different tomorrow,” he says. “Some of the trash trailers do get some of the lightweight stuff put on because it may be a lightweight load going out but it may be a load of trash coming back in. It’s up to them to make sure that it’s cleaned up so there’s no contamination.
“With some of these applications, we’re figuring that if we get five years out of them, we’ll be lucky and they’ve been used up and it’ll be time to trade them in and get something new. Some of them we’ve got running are about 10 years old; that part of it we’re still tracking.”
Floor durability is also a major concern at Riccelli Enterprises, an East Syracuse, NY–based hauling company that serves the entire Northeast with a fleet of about 300 moving-floor trailers. Matt Simmons, vice president of operations, indicates that Riccelli probably demands more from its transfer trailers than the typical MSW hauler from a ruggedness standpoint. That’s because the company uses the same trailers to haul fine aggregates and refuse.
Early in 2008, Riccelli installed some new Narrow Leak-Resistant Heavy-Duty (NLRHD) floors in eight of its trailers whose moving floors had been damaged by load leakage.
A significant amount of material was falling between the slats, so Simmons and Riccelli approached its floor manufacturer about designing a new severe-duty moving floor. The two companies collaborated on designing the NLRHD floor.
The floor incorporates a quarter-inch aluminum deck with a three-eighths-inch lip that overlaps the next slat and covers the seal to form a shock-absorbing ridge. Another five-eighths-inch ridge runs the full length of each deck slat for additional strength. In operation, every third slat moves together, pulling the load toward the discharge end of the trailer. The heavy-duty floor is designed so that the ridges in the floor take the brunt of heavy, abrasive material loading. The slats can be snapped into place at the time of installation, or if previously installed slats need replacing.
“This floor could be used by a company that hauls both trash and C&D material,” Simmons argues.
Innovations Improve Profitability, Safety
In recent years, trailer manufacturers have added a couple of options that are designed to improve fuel mileage and driver safety, respectively: an open air-flow tailgate and a front bulkhead man gate.
The open airflow tailgate is designed to reduce fuel consumption when the truck is driven empty. The airflow gate opens inwardly so the air flows easily through the trailer for less drag as well as easier handling.
Drenth reports that the specially designed tailgates save KRD Trucking about a tenth or two per mile on fuel mileage. “We have used the airflow gate,” adds Gray. “The air-flow gate works very well for fuel economy if you’re running a very long operation where you’ve got to go a couple hundred miles empty. It does help in terms of aerodynamics. We use them only on particular long-haul operations.”
Gray worked with Mac Trailer to design the front bulkhead man gate, which is located at the front of the trailer to allow the driver to enter the trailer without having to climb up the side of the trailer. “From a safety standpoint, it keeps the driver from climbing through the tailgates and over top rails; they can just walk through the trailer to clean it out. It was a big safety issue; we had several issues with falls and worker’s comp claims over the past couple of years, so we said why not put a door in the front.”