Equipment World Digital Magazine
Issue link: http://read.dmtmag.com/i/217452
machine matters | by Richard Ries COMPACT EXCAVATORS HAVE UNIQUE SPEC'ING CHALLENGES The key to spec'ing compact excavators in the 2- to 3-metric-ton range is to understand their potential and their limitations. T he first step in spec'ing compact excavators in the 2- to 3-metric-ton range is to define what they are and what they aren't.What they are: versatile machines that are as much tool carriers as excavators and often replace hand labor.What they aren't: full-size excavators.This means they shouldn't be spec'ed the same as their big brothers. Our sources were asked to provide what they thought were the top five specs for compact excavators and explain why these specs mattered most.There was a lot of agreement and some interesting variations. In the "what they aren't" category, Randy Hall of Kobelco explains that "because these aren't production machines, the specs that apply to larger machines don't always apply here." He cited swing speed, bucket capacity, dig depth and breakout force as examples.Yet others placed dig depth and breakout force on their list of top priorities. Hall notes that most of the digging done by compact excavators is done at far less than their maximum dig depth, often as little as half that depth.And "breakout force still matters in this size class, but less than on larger machines. It must still be sufficient for the intended applications but may not be enough for working frozen ground." 26 December 2013 | EquipmentWorld.com Nominal overhang versus zero tail swing Both designs have advantages and limitations. Nominal overhang, also called traditional overhang or compact radius, retains balance at greater reach and dig depth and allows a higher lift capacity.The longer body also provides more space, which makes more room for the operator and improves access to service points. But the overhang limits maneuverability and creates a risk of property damage during operation if the body strikes a structure. Zero tail swing (ZTS) performance is the exact opposite: reduced reach, reduced dig depth, more cramped operator space and more restrictive access to service, but greater maneuverability. ZTS machines can be equipped with counterweights to provide the balance of a nominal overhang machine, but then you've lost the advantages of the ZTS design.And unless the front of the machine is also changed out, the reach and dig depth are no greater than they were before the counterweight was attached. Some manufacturers address this by offering a package of complementary components. Deere, for example, offers a long-arm package for their 27D that includes a counterweight. The characteristics of both styles of machine