New Cat Wheel Tractor-Scrapers Feature New Designs, Technology

Thu June 02, 2011
Aggregate Equipment Guide

The Cat 621H, 623H and 627H wheel tractor-scrapers are designed to deliver enhanced productivity and enhanced operator comfort and efficiency through the use of increased power and capacity, new structures, electronic controls and ergonomic design. The new H Series designs change the way wheel tractor-scrapers look, run and ride — and increase their capabilities to move material at the lowest cost per ton, according to the manufacturer.

H Series wheel tractor-scrapers build on the durability and productivity of previous models. Sequence assist and load assist automate many of the operator’s most demanding tasks, and when combined with Cat grade control, the new systems unburden veteran operators and help less experienced operators reach high productivity levels more quickly.

With the H Series introduction, Caterpillar is offering the 621 in a push-pull configuration for the first time. The system enables two scrapers to work together when loading, rather than requiring a push tractor. Other scraper models have proven that the push-pull configuration is the low cost solution in many applications.

The new H Series machines replace the equivalent G Series machines when commercial production begins in August of this year. Each of the three models will be available with engines that meet U.S. EPA Tier IV Interim and EU Stage IIIB emissions standards and with engines for use in other regions.

The 620H Series wheel tractor-scrapers maintain the G Series configurations. The 621H is a single-engine, open bowl machine; the 623H has an elevating scraper and a single engine; and the open-bowl 627H has twin engines — one on the tractor and one on the scraper — and all wheel drive. Capacities are increased 2 cu. yds. (1.5 cu m) to 24 cu. yds. (18.3 cu m) for the 621H and 627H. The new bowl design is easier to load than the G Series bowl and has proven to enhance production, according to the manufacturer.

The 623H bowl maintains 23 cu. yds. (17.6 cu m) capacity, but the elevator is stronger, more powerful and easier to adjust.

New Engines and Drive Train Controls Improve Performance and Operator Comfort

The new H Series wheel tractor-scrapers feature a more powerful engine in the tractor and a more powerful engine in the scraper of the 627H. The Cat C13 engine in the tractor produces 407 hp (304 kW) — 18 percent more power compared to the G Series. And the C9.3 on the 627H scraper produces 290 hp (216 kW), an increase of 19 percent from the G Series machine. The new torque converter coupled to the scraper engine is designed to put more power to the ground.

New software ensures integrated performance of the engine and transmission. The 8-speed planetary powershift transmission hardware is the same as the G-Series unit, but new controls and software drive greater performance. The system manages the torque converter and transmission to provide smooth operation, which enhances operator comfort and extends component life. Performance on grades and coming out of the cut is noticeably better through sustaining torque through shift points. On flatter hauls, shift points are optimized for a balance between fuel economy and performance.

Complementing the new power train and higher capacity are wet disc service brakes. The new brakes are similar to Cat off-highway truck brakes. The H Series machines also introduce engine compression retarding and the elimination of hydraulic retarding. Engine compression retarding can be modulated within low, medium or high ranges to optimize cycle times.

Technology Assists Operator and

Reduces Rework

Caterpillar offers three new integrated technology options on H Series wheel tractor-scrapers. Sequence assist is available on all three models and uses integrated software and position sensing cylinders to automate many of the tasks an operator performs when loading, hauling and dumping. The operator simply sets preferences for bowl and apron height and subsequently pushes a button to ready the machines for loading, then for hauling, then dumping, and then the return to the cut. The system automatically sets the cushion hitch, bowl height, apron, ejector and elevator. Sequence assist comes with a convenient load counter for tracking material moved.

Load assist is available on the 621H and 627H models. It builds on sequence assist by loading the bowl with the push of a button. As the machine enters the cut, the operator can activate load assist so the system takes over control of the cutting edge height, limiting tire spin based on integrated sensors and GPS technology to ensure consistent and full bowl loads. The operator is responsible only for the throttle and steering. Load assist helps make inexperienced operators productive more quickly.

Cat grade control is available on all three models and is designed to work seamlessly with sequence assist and load assist. Using satellite positioning technology, the system ensures cut protection by limiting how deep the scraper will dig. The optional system is available from the factory and fully integrated into the machine. The system also puts the site plan in front of the operator for increased efficiency and elimination of rework. Another benefit of Cat grade control is site mapping using the scraper.

New Cab and

Operator Station

The new cab is designed specifically to accommodate the tasks involved with operating scrapers. It’s 21 percent larger than the G-Series cab, which gives the operator more room for movement and allows more window area for an expansive view of the work area. Also new and designed specifically for scrapers is the Cat advanced ride management system. This new system, which is in testing and will be available soon after H Series machines go into commercial production, is a seat suspension that dampens vibration and prevents end-stroke shock loads.

As part of the improved ergonomics, the steering column and pedals align with the right front post of the cab. This puts the operator in a more comfortable position when the seat is turned 30 degrees. A T-handle implement control is designed to fit comfortably in the palm of the hand and is aligned with the seat armrest for comfortable operation. The new wheel tractor-scrapers also feature multi-function hydraulics. The optimized hydraulic system, which uses piston pumps rather than vane pumps, enables the operator to operate the apron, ejector and bowl height control at the same time for faster cycle times.

An integrated dash group offers displays for the optional Work Area Vision System (WAVS). Cameras on the machine provide views of the cutting edge, right side and rear. The system enhances safety and provides a new way to see the cutting edge during loading and to see to the rear of the machine when performing push-pull work with another scraper.

An optional powered access ladder facilitates getting in and out of the machine. The ladder raises and lowers, tucking up under the cab when not in use.

A new cushion hitch configuration also enhances operator comfort. The 620 Series hitch has two accumulators — one high pressure and the other lower pressure. The high pressure accumulator softens the ride when the machine is loaded, and the lower pressure accumulator optimizes dampening an empty bowl.

For more information, visit www.cat.com.

This story also appears on Construction Equipment Guide.