The tractors have adjustable drawbars, so when you couple the scraper to the tractor, make certain the drawbar height is right for the scraper. “If the scraper is getting too high, when you lower the scraper, it will sit back on its heel and will be very difficult to load,” says Lewno.
As an alternative to conventional scraper tractors, there are tractors based on articulated dump trucks (ADTs). “You may want to consider an ADT power unit, which will greatly increase your haul road speed,” says Goossen.
For example, the Bell 4206D scraper tractor is derived from a heavy-duty articulated haul truck with specific scraper application enhancements to the drivetrain. The Terra Titan S4412 uses a high arch, or gooseneck-style, drawframe mounted to a ball hitch located near the center of the tractor.
As the S4412 scraper loads, the weight of the growing load is transferred to the center point of the tractor, which is equally distributed across both tractor axles. “This design utilizes the payload to increase traction as the scraper loads. No supplemental weights are necessary,” says Baty.
The use of grade control systems with pull scraper systems calls for special consideration.
“You need high auxiliary flow rate from the couplers,” says Rust. “Most new tractors are ‘plug and play’ and integrate with automatic machine control systems. Older tractors may require additional electric-over-hydraulic valve systems.”
Sufficient flow is needed to ensure fast, predictable hydraulic response for all functions. “Case IH requires at least 57-gpm hydraulic flow on its scraper tractors, and there is a 3/4-in. coupler option,” says Lewno. “That would minimize the restriction going back to the scrapers for increased speed.”
Plumbing a scraper setup also requires careful attention. “The industry standard quick-connection couplers may cause problems,” says Goossen. “Direct plumbing hydraulics is often the preferred choice and gives you the most hydraulic flow. When hooking up a K-Tec scraper, you will need a free-flowing hydraulic valve called a ‘CASE Drain’ to activate the automatic ride control. K-Tec’s automatic ride control allows for faster travel speed, while causing less stress to both the tractor and scraper.”