RESEARCH & DEVELOPMENT
Edited by Ken Korane • Contributing Editor
Novel circuit boosts machine efficiency European researchers recently wrapped
because there are frequent situations where the main arm and articulating arm act simultaneously, offering the potential to transfer energy between the two and make the motion significantly more efficient. Within this system, as shown in the accompanying diagrams, the hydraulic transformer HT1 connects the inner boom cylinder (IBC) with the outer boom cylinder (OBC), said researcher Chris Geiger of the Karlsruhe Institute of Technology (KIT). And actuating valve section VS1 creates hydraulic parallel movement that permits quasihorizontal extend or retract movement of the grapple. For example, during extension movements, the power of the lowered IBC transfers via HT1 to the OBC, resulting in retraction in the latter with minimal additional flow from the main pump. Tests conducted on the new design against a reference cycle showed an average energy consumption of 76 Wh per cycle for the HT system compared to a comparable conventional system with 90.3 Wh. On average, it achieved an energy savings of 15.8%. There was also a slight reduction of cycle time over a complete loading cycle, to 18.9 sec from about 20 sec, resulting in at least constant productivity with the new hydraulic system, said Geiger. Drive-train efficiency. The prototype used a hydrostatic-mechanical powersplit transmission from Dana Rexroth that reportedly combines the best properties of a mechanical transmission with those of a hydrostatic travel drive, and is technologically advanced in that it provides an infinitely variable speed output. The unit reportedly is far more efficient than the industry norm. Technicians tested the power-split transmission under reproducible conditions on
up the three-year Forwarder2020 project, which aimed to develop a next-generation forwarder that’s more efficient, productive and environmentally sustainable than anything currently in use. Engineers are now reporting preliminary findings from lab tests and field trials, with encouraging results. Forwarders are articulated vehicles that carry felled timbers from the woods to a roadside landing for subsequent loading onto log trucks. Among the objectives of the project: reduce ground pressure under the wheels to avoid deep ruts, improve fuel economy, offer higher travel speeds and reduce woodextraction costs. To address these requirements the project team designed several new technology “modules” that included the hydraulics, transmission and suspension. They were integrated into prototypes using an HSM 208 F from Hohenloher Spezial-Maschinenbau, NeuKupfer, Germany, as the base platform. Tests at several forest sites across Europe produced some notable insights. Working drive efficiency. One key feature of the Forwarder2020 prototype is a hybrid hydraulic system for energy recuperation and regeneration in the machine’s Palfinger Epsilon S11F crane. The crane is made up of a pillar, main arm (inner boom) and articulating arm (outer boom), as well as related cylinders and grapple. The circuit includes a hydraulic transformer, consisting of two fixeddisplacement hydraulic motors whose shaft ends are mechanically connected via a coupling. The transformer is important 28
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Research 12-19_FPW_V3.indd 28
12 • 2019
Conventional crane circuit
Crane hydraulic-transformer system
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12/16/19 2:41 PM
