Caterpillar Showcases New Hydraulic Hybrid Excavator

Caterpillar makes the case for Hybrid Technology by rethinking the way an excavator is made.

Thu April 11, 2013 - National Edition

A look under the hood of the Cat 336E H hydraulic hybrid excavator.
A look under the hood of the Cat 336E H hydraulic hybrid excavator.
A look under the hood of the Cat 336E H hydraulic hybrid excavator. From the outside, the 336E H looks similar to its non-hybrid counterparts; it was designed to be familiar to operators who have used older models of the excavator. Here it is pictured digging into the dirt of the Cat arena in Peoria, Ill. Using the latest 3-D technology, observers can view a virtual model of the Cat 336E H hydraulic hybrid excavator and get a peek into any portion they want. The muscular MH3049 material handler stands tall at the Cat demo yard. The MH3049 makes picking up and moving objects more than 2,000 lbs. (907 kg) seem like child’s play. The hydraulic cab-riser system on the MH3049 features “ground entry and exit” with a step-in cab, enhancing safety for operators and service personnel.

Caterpillar recently announced several major new products added to its line, chief among them the new Cat 336E H hydraulic hybrid excavator.

The press was given an advance sneak peek at the new machine at an event held at its Peoria, Ill., headquarters. The unveiling comes after months of speculation about the new model.

“Customer interest has been off the charts,” said Ken Gray, global product manager of large hydraulic excavators, Caterpillar’s excavation division. “They’re not only reaching out to Cat dealers to learn more about the 336E H, they are placing orders. In fact, we received our first signed orders October 17, the day after the reveal.”

The Cat 336E H, which on its surface looks similar to existing non-hybrid models, has been retooled under the hood based on three principles: Conserve, Optimize, Reuse.

The Conserve option runs the engine at its optimum speed. Energy flow is controlled and optimized via the patented Cat Adaptive Control System (ACS) valve, and energy is reused via the hydraulic hybrid swing, which captures the excavator’s upper structure swing brake energy in accumulators and then releases the energy during swing acceleration. It all adds up to a three part system that is designed to reduce fuel usage by as much as 25 percent over the 336E standard model, and 33 percent over the previous 336D standard model.

As far as cost goes, the new hybrid model will come at a premium but, according to Cat, because of the fuel savings, the cost can be recouped within one year to 18 months over the price of a non-hybrid model, depending on usage.

Since much of the design changes of the hybrid excavator are under the hood, Caterpillar has developed a 3-D model of the entire excavator that allows users to see every single detail of the interior. The model, which was displayed by Brian Stelbrink, Caterpillar’s product application specialist, was displayed on a wide touch screen that allowed users to see deep into the inner workings of the engine, the adaptive control system, and even into places that usually only mechanics can get into. “It’s really helped people visualize what’s going on inside,” said Stelbrink.

For anyone waiting to get a chance to utilize this new model, factory shipments began in March of this year.

In addition to the hybrid excavator, Caterpillar unveiled the first of several new wheeled material handlers in the MH3049.

According to Cat, high strength structural steel and advanced welding techniques ensure structural integrity; a powerful hydraulic system provides rapid response with efficiency; a Cat C9 ACERT engine delivers reliable, fuel-saving performance; and new serviceability features simplify maintenance. These design elements combine to provide low-cost operation and maximum value for the MH3049 customers.

According to Cat, major structures use continuous welds that incorporate extensive chamfering and beveling to reduce stress concentration. Both the booms and sticks are constructed from single piece top and side steel plates eliminating the need for seams and internal baffles.

The upper frame is designed specifically to dissipate loads transferred through the front linkage and counterweight, and the lower frame’s unique tapered design evenly distributes loads and reduces stress. Oversized pins and bushings strengthen pivot points. In addition, extensive finite element analysis and strain-gauge testing throughout the design process ensure long-term durability.

Also on the MH3049, the hydraulic cab-riser system features “ground entry and exit” with a step-in cab, enhancing safety for operators and service personnel. Cab height on both machines is adjustable up to an eye level of 18.75 ft. (5.70 m) on the MH3049 and 23.5 ft. (7.2 m) on the MH3059. On the MH3049, raise time from ground level to maximum height is approximately 14 seconds; lowering time from maximum height to ground level is 12 seconds. Similarly, the raise time from ground level to maximum height on the MH3059 is approximately 17 seconds and lowering time from maximum height to ground level is 13 seconds.

Adjustable sensors control the height of the cab above the ground. A manual safety override in the cab allows the operator to lower the riser in the event of engine power loss.

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