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Posted: 11/11/2015

Know the Basics: Compact Excavators 101

Bobcat Compact Excavator

Compact excavators (sometimes called mini excavators) are classified as machines with an operating weight of 10 metric tons or less. They emerged in North America in the mid ‘80s and have grown tremendously in popularity. Compact excavators are versatile machines built for a simple purpose — fast, efficient trenching or excavating. Their advanced hydraulic systems cam outperform larger tractor loader backhoes, and they offer greater flexibility to dig adjacent to objects, place spoil or load a truck. It is not uncommon to see a compact excavator being operated in conjunction with a skid-steer or compact track loader, because the machines complement each other.

Compact excavators have four main parts (see image):

  1. House – Contains the operator’s compartment, engine, hydraulic pump and distribution components. It’s attached to the undercarriage with a swing bearing. The house and workgroup rotate or “slew” 360 degrees on the undercarriage to provide exceptional agility when working in confined areas where larger machines cannot fit.
  2. Undercarriage – The legs and feet of the machine that get you where you need to go. Standard rubber tracks surround the drive sprockets, rollers and idlers which propel the machine. Rubber tracks minimize damage to established surfaces, such as lawns and patios, for less repairs at the end of a project. Steel tracks are available as an option for applications where a more durable undercarriage is needed, such as demolition or recycling centers.
  3. Workgroup – The boom, dipper (or arm) and an attachment. Buckets are the most common compact excavator attachments, but more than 15 attachments are available to increase the machine’s versatility. 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 tracks.
  4. Backfill blade – Hydraulically activated and controlled from inside the excavator cab, the blade is connected to the undercarriage and used for grading, leveling, backfilling and dozing. Depending on its position it can be used as a stabilizer for the machine. If you need to backfill and grade quickly look for the angle blade option. This option lets you angle the excavator’s backfill blade 25 degrees left or right, allowing you to direct spoil from one side to the other.

Compact excavators are specifically designed for trenching and excavating, especially in areas where larger equipment can’t fit. Unique features help you do your job faster, more comfortably and more efficiently.

Here are some of the key excavator advantages compared to larger machines:

Small size/low weight — Get onto more jobsites
Work in confined or limited-access areas with greater agility. They are lightweight so you can tackle jobs with weight restrictions. Transporting compact excavators is easy: Simply load onto a trailer and properly secure it to save money on fuel.

Track undercarriage — With tracks, there are no flat tires!
Track flotation keeps you productive in muddy, wet or sandy ground conditions to tackle drainage work and waterline repairs. Excavators with tracks can easily cross narrow trenches and provide added traction. Tracks exert less ground pressure than tires, so you can work without rutting lawns or damaging established surfaces.

What’s ground pressure? It is the force that the machine exerts on the surface measured in pounds per square inch (psi). Lighter excavators don’t necessarily have lower ground pressures. It is a factor of total machine weight and track surface area. Compact excavators with track undercarriages are known for having low ground pressure because the machine’s weight is distributed across a wider area — the two tracks.

360-degree house rotation — Place spoil anywhere you want
You can dig in any position around the machine and easily see your work.

Visibility — Always see your work
Compact excavators are designed so the operator sits “offset” to the boom, providing optimum visibility to the trench. In addition, the boom swing is independent so you can dig alongside obstacles. Plus, you can rotate with the house to always face your work.

Backfill blade — Quickly backfill, level and grade
Use it with a bucket to pry out and move objects or stabilize the machine. The backfill blade also serves as a stabilizer for lifting and digging.

Independent boom swing — Spend less time moving the machine
Dig square holes without repositioning the excavator. Offset dig around or alongside structures and save time not having to reposition the machine.

Joystick controls — Operate the machine with your fingertips

Ergonomic controls keep arm movement and fatigue to a minimum during long work days.

Undercarriage designs

Supporting framework underneath the machine that the tracks are attached to.

  • Retractable undercarriage – Most common on smallest compact excavators, the H-shaped undercarriage can be retracted to temporarily reduce overall machine width. This is valuable when traveling through fence gates and small openings or when working in tight areas. Once you’ve gained access to the jobsite, the tracks should then be expanded to increase your digging power and performance when working over the side of the machine.
  • Fixed undercarriage – Most excavators come with a fixed undercarriage. The width of the undercarriage is typically a little wider than the house structure.

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

  • Swing boom - Most compact excavators are equipped with a swing boom. It is connected to a swing frame and then to the machine frame using a horizontal pin. It can be hydraulically pivoted left or right independent of the house and it can move up and down. The main benefit is its off-center mount, so you can easily see the bucket and hole
  • Knuckle boom (or articulating boom) - A variation of a fixed boom that’s mounted directly to the frame. It’s a multi-piece boom that only pivots 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. It can’t move left or right and you can only dig right in front of the excavator house. This is a common configuration on full-size excavators.

Arm Configurations
This choice helps you determine the dig depth and reach.

  1. Standard arm — Offers maximum breakout force, making it ideal when digging performance is your top priority.
  2. Long arm — Offers more reach and dump height to reduce repositioning and increased productivity. It’s especially efficient for footing work, utility excavation and ditch cleaning.
  3. Extendable arm — Provides the best of both worlds: (power) when it’s retracted or additional dig depth and reach (without the need to reposition) when it’s extended.

Tail Swing Configurations
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 in North America. Typically the rear of the house protrudes 10 to 24 inches beyond the width of the tracks. It’s good for more 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

Usually, zero tail swing excavators are a little wider than a conventional tail swing excavator. 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.

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