Equipment World Digital Magazine
Issue link: http://read.dmtmag.com/i/426956
December 2014 | EquipmentWorld.com 26 Trickle up, trickle down These mid-size com- pact excavators borrow features from machines in both bigger and smaller size classes. Tom Connor of Bobcat says among the features that have moved down from larger exca- vators are the hydraulic quick-attach, enclosed cabs with heat and air conditioning and rubber- over-steel tracks. "The fi rst two enhance productivity. The third reduces operat- ing costs by extending track service life while preserving the ability to operate with minimal machine matters | continued John Deere John Deere's 35G compact excavator features a Tier 4 Final 23-horsepower engine; an auto-idle feature slows engine speed when the pilot-control levers are momentarily released. The cab has a multifunction monitor and a new access door. Cat intro's "high-def" hydraulics on E2 series High-defi nition is a term normally associated with televi- sions, but Caterpillar is using it to describe a new hydraulic system that plays a crucial role in the company's next generation of E2 series compact excavators, including the 3.5-ton 303.5E2. One of the biggest challenges the company faced in bring- ing these machines to market was how to meet emissions regulations without sacrifi cing performance. The EPA is dictating what the engines can do, so Cat tweaked their hy- draulic systems to keep from having to sacrifi ce performance, hence the high-defi nition hydraulic system. "The primary change from our old valve to this valve is that it is a simpler architecture," says Jennifer Hooper, marketing development engineer. "It is still a load-sensing, fl ow-sharing system, but it offers effi ciency, controllability and precision because we removed all the complexity from the valve system." A simpler valve architecture reduces heat, which reduces hydraulic instability, so you pack in more hydraulic power without having to increase engine size or horsepower, she says. The 303.5E2 also employs something Caterpillar calls "smart technology." Every manufacturer, Cat included, has dropped the horsepower of their 3.5-ton excavators below the 25 horsepower threshold where emissions regulations kick in, says Greg Worley, senior project engineer. "But we were not prepared to cut horsepower by 20 percent and say to our customers, 'Hey that's it, that's what you get,' because nobody buys a 3.5-ton machine and expects to get less performance." In the face of these horsepower cuts, Cat borrowed the computer-controlled pump technology from its F-series back- hoe and adapted it to the 3.5-ton excavator. "The F-series pump is an electronic pump, a pump with a brain," says Worley. "We've taken that same logic and put it in our 3.5- ton machine and called it smart technology." This pump senses and adjusts to altitude, ambient tem- perature, machine temperature, hydraulic load and AC load. "It takes all those parameters and maintains the machine's torque curve – totally invisible to the operator," Worley says. "We get the same performance with 20 percent less horsepower. According to the company, the 303.5E2 gets an 8-percent improvement in fuel economy and 7-percent greater effi ciency over the previous E-series. –Tom Jackson