Hydrostatic power splitting transmission optimizes reach stacker

Hydrostatic power splitting transmission optimizes reach stacker
Marginal Column

July 2016


Kalmar was looking for an alternative ultra energy-efficient hybrid-type of drive for its successful 'Gloria' reach stacker series. The solution was a new drive train system that combines well-proven efficient transmission technologies – hydrostatic and hydro-mechanical – with smart programming.

The Swedish cargo specialist Kalmar, part of Cargotec with headquarters in Helsinki, is a pioneer in energy-efficient container handling. Every fourth container in terminals around the world is handled by a Kalmar machine. One of their most successful products is the 'Gloria' reach stacker series. It can handle loads of up to 130 tons.

Mega trend towards energy efficiency

During development of the current fifth generation, one of the most important requirements was to obtain reduced fuel consumption with zero loss of driving dynamics and productivity. At the same time, improved ride comfort and enhanced handling and performance were to be achieved with optimum maneuverability. “On the one hand, this is due to the measures imposed by the tier IV stricter emission limits,” says Stefan Johansson, Director of Sales and Marketing at Kalmar, “On the other hand it's driven by the pursuit of lower costs for the vehicle operator.”

Teamwork for top results

It soon became clear to the development team at Kalmar that meeting these requirements required a new and innovative transmission concept. The development project was set up together with Dana Rexroth Transmission Systems (see info box) and the engine supplier Volvo Penta. Intensive teamwork was needed. “Close cooperation with suppliers is essential due to the far-reaching integration,” says Johansson. “Whoever wants to develop a highly efficient complete system needs to do more than just plug together components.” Alvin Anthony, Sales and Product Management at Dana Rexroth Transmission Systems, adds: “The challenge is to fine-tune and harmonize the various subsystems to produce an efficient system. This was only possible through extensive testing in real operation in cooperation with a dedicated pilot customer such as Kalmar.”

The result of the joint effort is the hydrostatic-mechanical variable transmission HVT including the appropriate transmission control. For the reach stacker from Kalmar, version HVT-R2 is specially designed with a transmission input power of 135-195 kilowatts. Kalmar is marketing the new drive line under the brand name 'Kalmar K-Motion'. The continuously variable transmission is based on an input-coupled hydrostatic-mechanical power split concept. In addition, the gears, couplings and hydrostatic components from Dana Rexroth come from a single source – and that facilitates service and maintenance.

Intensive field tests with record savings

During the first field tests, the pre-series reach stacker with HVT had already achieved fuel savings of up to 40 percent compared to an equivalent machine equipped with a conventional torque converter. The test cycle with multiple shifting and stacking of containers of different weights (10, 24 and 30 tons) over a distance of approximately 50 meters was handled by two machines at the same time and with the same handling capacity. The savings goals achieved by the reach stacker's new drive concept contribute to a significant reduction of CO2 emissions and are now also achieved in everyday use. “Depending on the specific application, we can even reach a reduction in consumption of up to 40 percent,” emphasizes Stefan Johansson. Many customers are impressed. Since the launch in the second quarter of 2015, Kalmar has already sold numerous K-Motion reach stackers – not only in Europe, but also in Asia Pacific.

The substantial reduction in consumption results from the combination of higher transmission efficiency and no torque convertor, with the downsizing of the combustion engine by around 20 percent. Instead of the previously used 11-liter diesel engine with 250 kilowatts, an 8-liter diesel engine with 201 kilowatts now does the job.

In work mode at the container, the new Kalmar reach stacker is characterized by comfort, low noise and easy controllability. Magnifier

In work mode at the container, the new Kalmar reach stacker is characterized by comfort, low noise and easy controllability.


High performance in work mode

In work mode when handling containers, i.e. at very low speeds, the new reach stacker from Kalmar excels thanks to its comfort, low sound pressure level, easy controllability and high degree of positioning accuracy. The purely hydrostatic first driving range offers the advantage of virtually wear-free, continuous and very dynamic reversing without the need to shift gears. This enables pinpoint positioning.

At higher speeds in the second and third driving range, the vehicle utilizes the high efficiency of input-coupled, hydrostatic-mechanical power splitting. Shifting between the different driving ranges is carried out without tractive effort interruption since the multi-disc clutches involved shift synchronously. A further advantage: With the design of the transmission, braking in all driving ranges is hydrostatic against the drag torque or the braking effect of the combustion engine. Stefan Johansson says: “With the energy-efficient K-Motion as the drive, we strike a chord with the customers. The reach stackers' low total cost of ownership and minimum downtime are the key to success at the cargo terminals around the world.”

The HVT-R2 continuously variable transmission. Magnifier

The HVT-R2 continuously variable transmission.

The best of both worlds

Under the name Dana Rexroth Transmission Systems, the joint venture between Dana Holding Corporation and Bosch Rexroth AG has been marketing hydromechanical variable transmissions (HVT) since October 2011. The HVT combines the advantages of mechanical drives with hydrostatic drive. This reduces fuel consumption and pollution emissions and improves the productivity and maneuverability of working machines.