Look at the visibility. Take 180º and note what you can see with the tractor. Look at maintenance. Those items that are going to give you a good cost per hour give you the competitive edge when you are bidding on a job.”
Finally, make sure the tractor is spec’d to provide optimum performance on your particular jobsites. The combination of track lengths, gauges and shoe widths complicate dozer selection. “For a Caterpillar D6R, you are probably talking 15 to 20 different configurations,” says Lynch. “So it gets rather complex. I don’t think customers always know how many options are out there.”
These choices allow an optimum solution for almost any task. “There are so many different applications, the biggest asset any of these companies has is to work with their dealer,” says Lynch. “They are the ones that really understand what goes on in a particular geographic territory and what other customers are doing in similar types of work.”
Hydrostatic vs. Torque Converter Drive
Dozers under 100 hp typically feature hydrostatic drive. This allows the tractor to maneuver more quickly in finish grading applications. “The hydrostatic transmission is beneficial in a utility application where maneuverability is required,” says Ronald Schultz, Caterpillar. But there is disagreement regarding the efficiency of hydrostatic transmissions in mid--size dozers.
Most mid--size dozers use powershift transmissions with torque converters. “With technology currently available, the best hydrostatic transmission is 5% to 15% less efficient than a powershift transmission with torque converter drive,” claims Schultz. “In cases where dozing performance is of key importance, a mechanical transmission will generate a higher percentage of engine power transmitted to the blade or ripper, given that both machines are well balanced.”
Schultz asserts that powershift transmissions can also tackle finish grading. “A powershift transmission, when backed by a differential steering system, can give the level of maneuverability to larger tractors when finish dozing is a required part of the owner’s needs,” he explains. There is also a trend toward electrohydraulic controls that simplify operation. “All of our machines are moving in that direction.”
Komatsu America also equips its mid--size and larger dozers with powershift transmissions with torque converters. They are coupled with the Komatsu Hydrostatic Steering System for ease of maneuverability, according to Ed Warner. “A torque converter allows you to have that ‘umph’ you need when you initially need to load the blade or if you are digging a stump. You just don’t get that with the hydrostatic transmission,” he claims.
However, Brett Errthum argues that hydrostatic transmissions in the mid--size John Deere dozers are just as efficient as torque converter drives, plus they simplify operation. “In the past, hydrostatic dozers had limitations,” says Errthum.
“We have a long--term relationship with our component supplier to develop pumps and motors specifically for our application. Really, the breakthrough came in better electronic controls that help divert the power to where it is necessary.
We have been able to overcome what has been the traditional downfall of the hydrostatic transmission on a large dozer.”
John Deere dozers use a load--sensing hydrostatic system. “When they sense that a load is bogging the tractor down, they will actually slow down the hydrostatics,” says Errthum. “By slowing it down, you are going to get more pushing power.” There is no need for the operator to shift the transmission to compensate for the load. “With a powershift transmission, you generally have three speeds,” he continues. “We have an infinite range.
It will just vary infinitely to the point that it needs to carry the load through. The operator doesn’t do anything that whole time. All he does is focus on that load in front of the blade, making sure his blade is positioned well as he carries the dirt forward.”