Class 8 trucks often transport materials over the road to the jobsite where they are stockpiled or dumped in front of dozers or motor graders that ultimately spread the materials. On construction sites and road building projects, dump truck drivers may also attempt to spread the material while unloading the bed.
Standard dump trucks can be used to place materials using a “tailgate spread.” This is when a driver dumps material out of the back of the truck while moving forward, using the chained tailgate to slow the flow of material while slowly raising the bed. But this is not a precise way to distribute material.
Many factors affect the quality of a tailgate spread, including the width of the area where the material is to be placed, steep areas or inclines and material stickiness. It becomes a real test of skill, since construction crews are relying on the drivers’ accuracy throughout material placement.
It takes a lot of practice to learn how different materials react to this spreading process. Sand will obviously move out much faster than gravel. The driver will also need to ensure the dump tray is being raised at the right speed. Too slow and the material won’t flow as required, and too fast will see too much of the material being laid.
Even the type of dump body can influence the results. For example, elliptical body designs lend themselves to uses where material typically hangs up. The elliptical contoured floor will assist with an easier flow.
In some cases, you can save significant time and effort by placing transported materials directly where they are needed with specialized solutions. You can save on the cost of support equipment as well as any labor needed to spread the material.
Unique Solutions Allow Accurate Placement
There are various options that allow more precise placement of materials directly from the transport vehicle. One of the more innovative methods is with a high-speed conveyor truck.
Unlike traditional methods, a high-speed conveyor truck unloads and places material in one motion, with one driver/operator. Other methods require a truck driver to deliver and unload the bulk material, plus additional equipment and crew to move the material into place where it is actually needed. The benefits of completing the operation in one motion include:
- Lower costs for equipment — no additional machines required to transfer and place material
- Lower costs for work crew — no added crew required to receive or handle material
- Time savings — off load and place a full truckload of stone or soil in a short period of time with minimal cleanup
- Material savings — no losses due to stockpile; place only as much material as needed, where needed
- Flexibility — one system places stone, topsoil, sand, gravel and mulch; 100-ft. range to work around obstacles and limited access points; deliveries scheduled independent of other tasks for jobsite crew
- Safety — less moving traffic and less congestion on jobsites; remote control allows less climbing and reduced dust and noise for operators.
“These factors combined result in lower total cost per load, and lower costs to complete the project in less time,” says Scott Nelson, W.K. Dahms Mfg. Ltd.
W. Keith (W.K.) Dahms developed a solution to transport and precisely place aggregate materials using a high-speed outboard rear conveyor mounted directly on a truck body. He named it the Stone Slinger.
“It was originally developed to deliver and place clear & frac 3/4-in. stone for foundations and weeping tile applications,” says Nelson. “Customers quickly adopted it for use with sand and gravel. Since then, the design has been modified to handle a broader range of material including topsoils, mulches and wood chips.”
The trucks are designed to precisely place materials via a movable conveyor. “The Stone Slinger is a hopper-style truck body with a live floor feed and a high-speed boom conveyor, which is configured to focus materials into a narrow stream as they are projected from the end of the conveyor,” Nelson describes. “The rig is controlled from an elevated station on the truck or with a wearable remote control package. Hydraulic valves allow remote control of the volume of material fed into the stream and the speed of the boom conveyor, as well as the conveyor’s angle of direction and elevation.”
These trucks can handle a range of materials. “The type of material will affect the Stone Slinger’s maximum effective range for placing material, but in general, it can handle the same material types that are suitable for delivery in a dump truck,” says Nelson. “In typical stone applications, a Stone Slinger system can accurately place material up to 100 ft. from the truck. The throwing distance will be less for light-density ‘fluffy’ materials. A shorter conveyor is also available for close-in applications such as roadway and sidewalk reconstruction in older, heart of city work.”
The operator directs the flow of material to where it’s needed. “To aim the material stream, the conveyor can swing laterally through a 270° arc, and can be raised or lowered through 46° of elevation, 23° above and below horizontal.”
The speed of placing the materials depends on how much precision is required. “In most high-speed applications where the conveyor is projecting the material over some distance, the Stone Slinger can unload upwards of approximately 3 tons per minute,” says Nelson. “The high-speed conveyor will unload and place a full truckload in about half an hour when very precise placement is required. If the application simply requires the load to be dropped in one place, the live bottom and conveyor will unload the complete truck in about four minutes.”
Remote Control Simplifies Placement
A remote control for the Stone Slinger not only controls the speed and direction of the conveyor, but allows the operator to remotely maneuver the truck around the jobsite. A single set of controls can run the conveyor and reposition the truck with Creep Drive for ideal placement of the material.
The Stone Slinger Creep Drive adds a complete hydrostatic drive system to the standard powertrain of the truck. A hydraulic-driven gearbox is inserted into the driveline. A CAN Bus panel controls all hydraulic and operating functions and communicates with the remote.
Ground speed of the truck under hydraulic power is limited to a fast walking speed. If the truck is on an incline, the hydraulics will brake its speed automatically. If the wheel speed exceeds 2.5 mph (4 km/h), the CAN Bus will shut down and stop the truck.
John Da Silva of Rock Concrete Forming Ltd., Mississauga, Ontario, has experience with the Creep Drive remote control on the Stone Slinger. He says the investment has paid off well. “It’s the time savings that pays you back,” he states.
“On a typical weeping tile job, the driver has to go back and forth to move the truck four or five times. Each time when you get into the truck, you have to turn the PTO off, drive the truck, put the air brakes on again and restart the PTO,” Da Silva notes. By using the remote control to move the truck, the operator remains outside the cab to keep the material flowing until the load is completely delivered.
Da Silva believes outside of the truck is the right place for operators to be. “You get out here and you can see everything,” he comments. “We are always working in very tight spaces. You can watch the wheels and the ground more closely than if you were steering from the cab. You won’t ever put the truck in a pothole or a ditch, so you never have to wait for another truck to come pull you out.”
The Creep Drive translates into better job quality with less wasted material, Da Silva adds. By making it easy to move the truck into the best location, Creep Drive helps operators distribute material more precisely and consistently. That translates into lower costs for clean-up and material.
Ejector Bodies Allow Precise Control
Another alternative to a standard dump body is the ejector body. These bodies feature an ejector ram installed in the bed of the truck that pushes material out of the rear without having to raise the dump body. Because a low center of gravity is maintained, the risk of rollovers that can occur when a body is raised is eliminated.
J&J Truck Bodies & Trailers, Somerset, PA, offers a Horizontal Ejector (HE) that allows precise control when unloading aggregates and asphalt. It features the DynaControl hydraulic system with AutoFeed, a hydraulic double-acting high-lift tailgate and the AWARE camera system.
AutoFeed automatically moves the load forward when the spreader is low on material. The AWARE camera system allows operators to see the position and operation of the ejector inside the body and ensures visibility behind the truck when operating in reverse.
“The horizontal ejector technology is a lower cost, easier to maintain solution than other conveyor/auger bodies currently on the market,” asserts Mike Riggs, senior vice president, J&J Truck Bodies & Trailers.
Whether high-speed conveyor trucks and ejector bodies are well-suited for your jobsite depends on a number of factors, including the desired cycle time and payload capability. You must carefully compare the payload weight capacity vs. the potential time, labor and equipment savings to determine the best solution for your operation.