When it comes to fine grading, automated grade control systems have certainly commanded a lot of attention - and for good reason. They can enhance efficiency, reduce rework and enable even less experienced operators to achieve grade more quickly. Yet, finish work typically encompasses only a small portion of a dozer's hours on a project.
"It depends a lot on the application, but you will spend probably 90% of the time doing what I would call 'material balancing' and rough grading to get things generally laid out according to the finished design plan," says Bruce Unger, New Technology Black Belt, Heavy Construction and Mining Division, Caterpillar Inc. "It's really when you only have the last couple inches left that you put it into automatic mode and make that final pass to get to that final spec."
For the largest percentage of a dozer's time on the job, it's up to the operator to take control. Thankfully, this has become much easier given the added "brains" incorporated into today's dozer designs, which enable these heavyweights to do some of the thinking for themselves.
An electronic shift
With the introduction of stricter emissions requirements, engine suppliers have been required to incorporate more sophisticated electronics into engine control systems. A side benefit is these electronics tend to facilitate better communication between various operating systems of the machine.
"The electronics are mandated to a point where it's impossible to meet emission levels at certain horsepower levels without fully electronically controlled engines," says Bernard Winker, manager of marketing and engineering services, Dressta North America. Depending on the powertrain system, this also means the engine and powertrain are able to communicate more effectively to control other machine functions.
"Most machines today have onboard computer technology, where the engine and transmission 'talk' to each other and make automatic adjustments to allow the machine to work at optimum efficiency," says Dan Drescher, product marketing manager - crawlers, John Deere Construction & Forestry.
For example, the engine and hydraulic control units on many of today's dozers work together to adjust operating rates and performance characteristics. "What you have today is the ability to adjust the speed ratios of your transmission, forward and reverse," Drescher notes. "Essentially, you tell the machine how fast you want to go - the maximum speed for a certain operation - and it will adjust up and down based on the load you have on the blade and the ripper."
"If an operator starts loading the tractor in second gear, for example... the transmission will determine that it is more efficient to kick down to first gear," Unger adds, "and it will automatically do that."
This takes the impetus off the operator to determine when it's time to upshift or downshift. "On some of our larger tractors... we let the computer decide when the torque converter locks up, because we find that the computer does a much better job of sensing conditions and when things should happen," says Les Scott, product manager - dozers, Komatsu America. "The guy in the seat has to feel or hear the engine lug down... He has to pick up some 'sign' that he's starting to overtax the tractor in that particular gear.
"By measuring ground speed and engine load, the [transmission] controller will shift at a much more opportune time to maintain your dozing production," he states.
"It's almost like an automatic-style transmission in a dozer," Drescher comments. "You don't have to think about shifting gears. It's always going to be at its maximum productive level, and you can focus on adjusting the load or maneuvering the tractor."
The growing shift from pilot to electrohydraulic controls is enabling suppliers to further simplify dozer operation. Gone are most of the manual control levers in favor of multi-functional joysticks.