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Posted: 08/26/2019

Know the Basics: Compact Excavator 101

Infographic detailing the different sections of a mini excavator.

Mini excavators, also known as compact excavators, are classified as earthmoving machines with an operating weight of 10 metric tons or less. They emerged in North America in the mid1980s and have grown tremendously in popularity. Their advanced hydraulic systems can outperform larger tractor loader backhoes, and they offer greater flexibility to dig adjacent to objects, place spoil or load a truck. Mini excavators are versatile machines built for a simple purpose – fast, efficient trenching and excavating. It is common to see a compact excavator operated in conjunction with a skid-steer or compact track loader, because the machines complement each other and can get work done faster than larger dedicated earthmoving equipment.

Mini Excavator Main Components

  1. House – Attached to the undercarriage with a swing bearing, the house contains your operator’s cab, engine, hydraulic pump and distribution components. The house and the workgroup rotate or “slew” 360 degrees to provide exceptional agility when working in confined areas where larger machines can’t fit.
  2. Undercarriage – The undercarriage includes standard rubber excavator tracks surrounding drive sprockets, rollers and idlers which propel the machine. The most common type of undercarriage for smaller mini excavators is the retractable undercarriage. This H-shaped undercarriage can be retracted to temporarily reduce overall machine width, which is valuable for traveling through small openings or working in tight areas. It should be expanded before doing any work. A fixed excavator undercarriage is typically a little wider than the house structure.
  3. Workgroup – The boom, arm and any attachment you add to the machine are all included in the workgroup. Compact excavators are unique in that their workgroup is connected to the front of the house with a “swing frame.” The swing frame can be hydraulically pivoted left or right so you can do offset digging parallel to the excavator tracks.
  4. Backfill blade – Hydraulically activated and controlled from inside the excavator cab, the backfill blade is connected to the undercarriage and used for grading, leveling, backfilling and dozing. It can also be used as a stabilizer for the machine depending on its position. An angle blade option is ideal if you need to backfill and grade quickly. This option lets you angle the excavator’s backfill blade 25 degrees left or right to direct soil from one side to the other.

Versatility Features

Mini excavators are specifically designed for trenching and excavating in areas where larger equipment can’t operate. The auxiliary hydraulic lines routed on the machine’s boom and arm provide the power you need to use a variety of excavator attachments, and the compact size and low weight help you navigate more congested jobsites that are otherwise out of reach. Transporting compact excavators is also less complicated and saves money on fuel due to their reduced size. Simply load the excavator onto a trailer and properly secure it

Excavator track flotation is another key feature that keeps you productive in muddy, wet or sandy ground conditions. Mini excavator tracks can easily cross narrow trenches and provide added traction. Their tracks also exert less ground pressure than tires, so you can work without rutting lawns or damaging established surfaces.

Mini excavators are designed so the operator sits “offset” to the boom, providing optimum visibility to the trench. The boom swing is also independent, so you can dig alongside obstacles with fewer restrictions and greater visibility.

Boom Configuration Options

The primary component of the workgroup that’s attached to the house, the boom supports the arm and attachment. There are three main boom configurations:

  • Swing boom – Most mini excavators are equipped with a swing boom, which is connected to a swing frame and then to the machine frame using a horizontal pin. The swing boom can be moved up and down as well as hydraulically pivoted left or right, independent of the house.
  • Knuckle boom (or articulating boom) – Mounted directly to the frame, the knuckle boom is a variation of the fixed boom. It’s a multi-piece boom that only moves up and down. The outer part hydraulically swings left or right, but the arm stays parallel to the machine.
  • Fixed boom – Mounted directly to the frame, a fixed boom can’t move left or right, so you can only dig in front of the excavator. This is a common configuration on full-size excavators.

Arm Configuration Options

Different arm configurations help you handle varied dig depth and reach when operating your machine. There are three arm configuration options:

  • Standard arm – This option offers maximum breakout force, making it ideal when digging performance is your top priority.
  • Long arm – With the long-arm option, you have more reach and increased dump height to reduce repositioning and increase productivity. It’s especially efficient for footing work, utility excavation and ditch cleaning.
  • Extendable arm – This option provides more power when it’s retracted and additional dig depth and reach when it’s extended. Approved for select models, Bobcat clamps can be used with the extendable-arm option on mini excavators.

Tail Swing Configuration Options

Tail swing is defined as the rear overhang of the house as it rotates on the undercarriage. It’s measured from the center rotational axis to the furthest rear point of the machine. There are three main categories:

  1. Conventional tail swing – The most common configuration in North America. Typically the rear of the cab protrudes 10 to 24 inches beyond the width of the mini excavator tracks. This is ideal for gaining additional lift capacity but can limit working in tight spaces.
  2. Minimal tail swing – The rear of the house protrudes slightly (up to six inches) over the tracks, making it easier to work in tight work spaces.
  3. Zero tail swing (ZTS) – The rear of the house doesn’t project beyond the tracks. Depending on the model and make of the machine, the ZTS design allows the operator greater flexibility to slew and deposit spoil without concern of inadvertently contacting surrounding objects.

Zero-tail-swing excavators are traditionally a little wider than conventional-tail-swing excavators. If your biggest obstacle is gaining access through gates or narrow paths, or maneuvering into a crowded worksite, a conventional-tail-swing compact excavator might be your best choice.

Ready to see all these features in action? Contact your local Bobcat dealer to schedule a demo today.

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