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Excavators are like musical instruments in that they remain inanimate objects unless there’s someone who can access their potential. However, unlike most musical instruments, excavators have engines to move the vehicle and operate the hydraulics to enable a number of tasks. the core one of which is excavating – the shifting of soil or rock from one place to another, so replacing teams of men with shovels. Highways Today tells me the patent for the first excavator was granted to William Otis in 1839 for a steam-powered excavator mounted on a train chassis. That’s it on the left below. The boom, arm and bucket are operated by levers and pulleys and must have included at least one clutch to direct the power of the engine. This basic configuration remained unchanged until the mid-1950s but is still used for tasks that require only the scooping up of sand, rock or ore and loading it onto a nearby tip-trucks. Early excavators were called shovels because that was the name of the tool they replaced and the activity they performed.

The first hydraulic excavator was by the Kilgore Machine Company in 1897. It used water as the hydraulic fluid. The compact hydraulic excavator as we know it was developed in Japan in the 1960s for use on small building sites [thanks Plant Planet] and was only made possible by the advent of hydraulic conduits that were strong enough to withstand large pressures. The Yanmar Construction Company YNB 300 was the first compact hydraulic excavator. That’s it on the right below.

We now have a full range of sizes ranging from the KOMATSU PC-01 that’s the world’s smallest, to the Liebherr R9800, currently the world’s largest hydraulic excavator.

The configuration of the compact hydraulic excavator remains substantially the same. The Bucket is connected to the Arm (a.k.a. Stick, Dipper) connected to the Boom connected to the rotating body called the Swing that, these days, is normally mounted on crawlers, though wheel-mounted ones are often used when agility and speed are required. 

Operation

An excavator has two Operation Lever (a.k.a. joysticks) moved according to either the ISO or SAE operating pattern. The two patterns are identical apart from left hand operations in one pattern being right hand operations in the other, and vice versa. Excavator operators were usually more comfortable with one or the other and swapping between them wasn’t encouraged, but operators of modern excavators can now switch the operating patten according to preference.

The images above and the following (ISO) descriptions are from Heavy Metal Learning.

Right Operation Lever
Boom: Push right lever forward for Boom Lower, and backward for Boom Raise.
Bucket: Rotate wrist the left for Bucket Roll-In (Dig) and to the right for Bucket Roll-out (Empty).

Left Operation Lever
Arm: Push the left joystick forward for Arm Roll-Out and backwards for Arm Roll-in Cab.
Swing: Rotate wrist to the left for Swing Left and right for Swing Right.

Travel Levers
Centrally positioned left and right levers control the speeds of the left and right crawlers. Pushing both forward as one, makes the excavator travel straight ahead, and so on.

Excavators aren’t complex pieces of machinery. The five working parts of Bucket, Arm, Boom, Swing and crawlers are controlled by the operator’s hands, as well as by ancillary foot pedals. The operator is therefore connected with the machine in a very physical way and, with practice and experience, operation becomes second nature. One basic operation is using the left joystick to swing the machine while extending the boom with the right. Another is to use the left joystick to extend the arm while using the right one to operate the boom while coordinating the dig and dump movements of the bucket. Skilled operators will increase efficiency by simultaneously performing as many of these actions as possible. Basically, the combination of man and machine makes the excavator into a traveling robot arm with about six degrees of freedom. As with robot arms, the required task has a suitable attachment for the end of the arm in much the same way as tools add functionality to human arms and hands.

Attachments

Bucket: This default attachment is for the excavator’s primary purpose and, in general, the size of the bucket is appropriate for the size of the excavator. There are eleven different types and choosing the wrong one can impact efficiency.

Thumbs: These are buckets with the addition of an opposable “thumb” or claw to grab objects. There are also more specialized ones called grapples as well as ones resembling pincers for precision work.
Rippers: Large punches usually used to make holes in concrete or asphalt surfaces prior to them being dug up.
Pulverizers: These do the same but are designed to crush rather than penetrate.
Stump harvesters: Holding tree stumps and apply force to lever them out.
Chuck blades: Cut through large roots or other horizontal obstructions.
Forks: Let the excavator be used as a forklift. (Visit https://www.amiattachments.com/excavator/ for a full range of excavator attachments.)
Hooks: There are also various types of suspension attachments for lifting although it’s common for someone on site to sling a rope over a bucket claw and shout out something like “Hey give us a hand with this!”

The basic functionality of the excavator lies in its versatile boom, arm and bucket combination but would be of little use without the swing because a common operation is to move earth, rock, trees or concrete from one place and either putting them in another place or loading them onto a waiting vehicle.

  • Better responsiveness gives the excavator the potential for precise control. The screenshot below is of an operator using an excavator thumb attachment to place one beer bottle on top of another before placing the ball on top. This degree of control explains why modern excavators are used for rescue work after floods and earthquakes.
  • Increased torsional rigidity of the boom, arm and bucket articulations so the three parts always stay in the same plane means the swing movement can be used to use the sides of the bucket to sweep a road clear of rocks or level a site of scrub. The swing and crawlers used to be thought of as conceptually separate from the boom-arm-bucket-swing combination because digging didn’t have much to do with travel but an operator could theoretically swing the arm assembly from side to side while traveling forward or backwards, thereby making the excavator function as a grader or roller. This new functionality was made possible by the increased torsional rigidity but it was up to an operator to discover and make use of it.
  • Increased brute strength of the swing-boom, boom-arm, and arm-bucket articulations means the bucket can now be used to bear the entire weight of the machine. Brute strength is an advantage on construction sites but, at some time, some operator must have realized that the increased strength-to-weight ratio made new actions and movements possible. The first image below shows the bucket dug in at the higher level and the arm assembly being contracted to pull the excavator up the incline. The second shows the bucket placed on the lower level and the arm assembly extended to push the excavator up the incline. Both techniques increase safety and lessen engine strain.
pulling up
pushing up
  • Torsional rigidity and brute strength is required for what I’ll call “walking the excavator”. This is is the action of using the boom/arm/bucket to lift one track over an object that can’t be driven over, and to then lift the other over. All five working parts of an excavator are being simultaneously deployed. Again, this functionality isn’t something the machine was designed to have but something an operator thought might be possible.
  • Torsional rigidity, brute strength and fineness of control (1) enables a special maneuver known as a jump turn or pivot turn. The bucket is placed firmly on the ground and the excavator driven towards it to raise the front end. The right track is driven forward and the left one in reverse (or vice-versa) while swinging the machine in the opposite direction. This operation can reposition the excavator in tight spaces but it chews up the ground and isn’t great for track wear either. The image on the right is an extreme jump turn demonstrating the excavator’s torsional rigidity, brute strength and fineness of control.
  • Torsional rigidity, brute strength and fineness of control (2) are often demonstrated to potential buyers by various maneuvers collectively known as “excavator dancing” or “excavator acrobatics” and are often seen at “excavator rodeos”. Fighter plane acrobatics at an air show demonstrate the capabilities of an aircraft to potential purchasers but there’s also an aspect of entertainment for the general public. Essentially, excavator dancing is a synchronous display of the same characteristics. HYUNDAI put a lot of effort into them.
  • Torsional rigidity, brute strength and fineness of control (3) is ostensibly about demonstration of the same three capabilities, but with a higher entertainment component. In theory, it should be possible for an excavator operator to make an excavator stand on its bucket – given perhaps an incline to help shift the centre of gravity. This trick would have no practical use and would take us firmly into the realm of entertainment spectacle. After all, how much demonstration does any new capability need? Let’s see … Yes!! It was a bit more than what I was expecting though. [Searching “excavator climbing” will take you to the video.]

The point of excavators isn’t to entertain but, if an operator thought something was possible and attempted it even though it was outside their “training set”, then it’s a noble endeavour and, of late, something we recognize as a very human thing. Acrobatics demonstrate the capabilities of the machine but they also demonstrate unique operator qualities such as curiosity, knowledge of the machine’s characteristics and abilities, and confidence in directing them. Let’s not forget safety. The ongoing setbacks in developing self-driving cars that can run accident-free in lines that are mostly straight, reveal the limits of developing automated systems for situations predictable only within the limits of their training sets. Excavators don’t move fast but they have heavy buckets with an additional four degrees of freedom that their operators deploy according to on-the-fly assessments of unfamiliar site conditions and unpredictable weather conditions. This is in addition to all the usual risks on the ground but also unseen ones underground in the form of conduits and pipes for utilities and other essential services. Of course, GPS and various other sensors can be added to increase precision or prevent operator errors to an extent, but excavator operation remains firmly manual and human-dependent.

The parallel histories of excavator evolution and excavator operation show us how improvements to the basic structure and mechanics of the machine can, with the addition of human ingenuity, give rise to new functionality and movements. Excavators are powerful but lack intelligence. Humans are intelligent but weak. Excavator and operator complement each other but the excavator doesn’t “augment” human capabilities any more than any other hand-operated tool does. Only when the human augments the machine with real intelligence is the excavator capable of doing anything. This clean and pure relationship between man and machine is worth hanging onto for as long as we can.

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https://www.fortunebusinessinsights.com/industry-reports/excavators-market-100861

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