Equipment World Digital Magazine
Issue link: http://read.dmtmag.com/i/407095
up as the load sheds off. You don't get that slight loss of momentum that comes with the shift. On slopes, turns under load, and for GPS and final grading applications, the hydrostats shine. "If you are set at a speed and encounter a change in the load, the operator doesn't have to do anything to downshift," Oliver says. "The machine will automatically manage the power to maintain that load. When it comes to live power turns, if you have a full blade of material you don't lose per- formance in in that turn, and that's very important." Hydrostatics also bring the benefit of dynamic brak- ing. You simply ease off the throttle and hydraulic pressure within the system will bring the machine to a stop. "If you're going up a slope and stop, you stop," Oliver says. "There's no rolling back- ward because the hydrostatic system will keep the machine from rolling back." Typically torque converters have the decel pedal, but they also have a brake pedal which requires two feet, says Wilson. On a hydrostatic you only need one foot for the decel pedal. This makes operation on side slopes, when you need that other foot to brace your- self, less awkward. Programing individual preferences One of the beauties of hydro- static transmissions is the abil- ity to electronically program on the display monitor in the cab how you want the machine to operate. "You can go in and make that tractor feel like two or three different tractors," Wilson says. You can program the shift breaks and dial in the ma- chine to the operator's prefer- ence. This includes things like the sensitivity of the joysticks and the decel pedal and steer- ing modulation. If the ma- chine has an electro-hydraulic valve you can change the way the blade feels and responds, Wilson says. Precision in pipe laying One of the more challenging jobs for a dozer is laying pipe in a trench. Here the machine needs to creep slowly forward while pulling a load that's weighted off balance on one side of the machine. "You're trying to ease the pipe down and inch the ma- chine forward. You've got guys down in the trench and for safety reasons you don't want the machine lunging forward," Wilson says. That's where the infinite speed control plus the ability to simultaneously oper- ate a hydrostatic winch comes in handy. "In one mode you can con- trol track speed and engine speed," says Wilson. "When you're coming close to the end you can push the decel pedal and engine and track speed both come down. In another mode with a push of a button you can decouple the engine speed from the track and ground speed. The engine speed and the hydraulic flow to the winch and blade remain constant, but you can slow your track speed to a crawl." "In that same operation with a torque converter, you have to select a forward gear and one gear could be too fast while the next lower gear is too slow," says Merle Hermsen, product application consultant. "It's hard to get it precise with a torque converter, whereas with a hydrostat you know exactly what it's going to do." November 2014 | EquipmentWorld.com 32 product report | continued Thanks to the hydrostatics, Merle Hermsen, product application consultant for Deere, can attack this steep slope at an angle, without having to fight track slippage and lose momentum. When carving a trench, load sensing hydraulics adjust the speed and power to the tracks as the blade loads up to pre- vent the machine from bogging down. Hydraulics mated to GPS machine control allow Merle to doze without touch- ing the blade controls. The GPS system senses the position and angle of the blade to within a few milimeters of accuracy and the hydraulics adjust the blade without needing input from the operator.