Komatsu PC138US-2 excavator

By: Thomas Duggan, Photography by: Thomas Duggan

Date: 10.04.2013

With an ultra short rear end and huge reach, Komatsu’s PC138US-2 excavator can tackle work in confined spaces

Komatsu PC138US-2 excavator

Smooth, fast hydraulics
Sliding cab door saves space
High boom lift
Great for work in confined areas
Good visibility

Weighing in at 13,480kg standard, this excavator tips the scales at a tad over 14-tonne due to its BAS tilting hydraulic hitch and a thumb. It is powered by a Komatsu SAA4D95LE-3-A engine capable of pedalling out 66kW and coupled to Komatsu's HydraMind variable displacement piston pump squirting a maximum of 226 litres a minute. Propelling the machine are Hydash final drives, which clamber along the track chains bolted to 500mm triple grouser shoes.

Maintenance

Looking at the ultra short rear end on the PC138, you wonder how they get all the vital innards to fit.

The back left compartment door reveals the batteries, air cleaner and cooling system. The outer most battery and air cleaner are easy to check and clean, but not so for the radiators and inner battery level.

Around to the opposite side is the pump compartment which houses the remote mounted engine oil filter, and with a tap on the sump, makes the 250 hour service easier. Behind the front right panel is the hydraulic control valve block, and sandwiched between the valves and pump room you will find the fuel and hydraulic tanks. At the front right is a small door to access the hydraulic control pattern changer, although it's not lockable. It is also fully enclosed under the boom and on top of the slew motor making it simple to keep clean and a great place to stand while checking the oils. There's a reasonable amount of room around the engine and the panel in front can be unbolted to allow more in-depth work. Under the cab is the toolbox, and there is a little room to store a grease gun and other basic tools.

Working environment

Entry to the cab is through a sliding door with well placed grab handles. Inside the cab there's not a lot of room, but enough for most to get comfortable. Visibility out the front is slightly narrower due to the curved cab; looking sideways and to the rear is good. With the aid of a large convex mirror mounted on the counter weight, it is easy to see the end of both tracks when looking out the back.

Operating the 138 is two joysticks and three pedals. The two pedals each control a track, with the third for the high flow hammer piping, currently running the thumb. The joysticks operate to whatever pre selected setting is chosen. Tilting the quick hitch is done by two buttons on top of the right joystick. The gauges and switches are well laid out and within easy reach.

Playtime

With a turn of the key the 89hp diesel fires to life. The PC138 has three work modes. I select A mode (heavy load operations) and rip into the ground. Even with the 2m wide bucket, it effortlessly digs into the gravel/clay mixed soil with excellent cycle times.

Considering the tilting hitch adds about half a metre between the arm pin and bucket pin, it doesn't lack crowding power. Within a few minutes I have a hole over 2.5m deep. While digging and slewing the machine stays stable.

Scrolling down to E mode (economy) drops the engine revs a few hundred and with it goes the hydraulic speed, but it seems too slow to be very productive - probably better suited to more precise work.

Pushing the down arrow again selects B mode (breaker) which decreases the revs even more so that it provides the correct oil flow for a rock breaker.

Back to A mode and full revs, I walk down into the creek and up a steep bank. With the tracks rotating and the machine no longer moving forward, I give it some assistance with the dipper arm and it continues its climb to the top, the load sensing valves in the closed centre hydraulic system provides oil to all functions at once, making combined movements a breeze.

The PC138-2 is very nimble and user friendly. The two-speed tracking system changes from high to low automatically with a top speed of 5.1kph. In low gear it produces 123kN of drawbar pull providing plenty of power for steep work.

With a heaped bucket of heavy wet soil at full reach over the side, I can feel that there's not much weight on the back track - not bad considering there's over 450kg of extra steel hanging out there in the hitch and thumb. With the help of the thumb I grab an old tractor destined for scrap and lift it well clear of the ground. I am very pleased with the smoothness of the hydraulics, with small movements of the joysticks the bucket can be precisely positioned, with no jerkiness. Even on standard 500mm shoes when slewed to the side, the counter weight only protrudes by a small 235mm, making it well suited to confined spaces.

So that all the main organs still fit into its compact body, the boom is mounted further forward than a standard excavator, giving it an increased reach. The boom also lifts a lot higher to reduce its front swing radius, allowing huge benefits in tasks such as demolition and tree removal

Summary

With its compact size and huge reach I would choose the Komatsu PC138US-2 for its smooth, precise and fast hydraulics. Although it lacks a little bit in stability, it can be spec'd with additional counter weight and wider shoes.

When compared to a standard swing machine you could definitely tackle a lot more difficult confined work with this machine making it more versatile and worth its 6% price premium over a conventional digger.

The latest model

The newest model Komatsu excavator is the PC138US-8. Key features include: