Mowing on steep slopes - well balanced

The Gekko is part of the programme of Köppl GmbH in Saldenburg/Lower Bavaria, which enjoys a good reputation worldwide as a premium supplier of single-axle motorised implements for soil cultivation and landscape maintenance. Köppl develops and manufactures various implement carriers - always with a single axle, always with a combustion engine, powerful hydrostatic drive and mechanical PTO shaft for driving the attachments and working tools. With this clear profile, the company, now managed by Karl Köppl in the fourth generation, has achieved that the implements are exported worldwide and that Köppl also develops special implements for the requirements of agriculture, e.g. in Africa and India. The appeal of "Made in Germany" contributes to the company's sustained successful development, as does its innovative strength, which is demonstrated not least by the Gekko.

When developing this trade show motorised device, the focus was on achieving a high mowing performance (with a cutting width of up to 5 m) even on very steep terrain. This is achieved, among other things, with a low centre of gravity with high ground clearance, a widened axle and two independently operating hydraulic wheel drives. In addition, the designers have realised a special innovation with the "Self-Balance" function. Benjamin Roll, Head of Design at Köppl GmbH: "The axis of the Gekko can be moved by 300 mm in the longitudinal axis." This changes the weight distribution between the axis and the attachment.

In practice, this function, known as "self-balance", is used so that the axis moves closer to the implement or further away from the cutter bar, depending on the gradient and uphill or downhill travel. Incidentally, people do a very similar thing: when walking uphill or downhill, they unconsciously change the length of their stride in order to always have a secure footing and maintain their balance.

When realising this idea, the designers were faced with a challenge resulting from the operating conditions. "The mechanical stress is very high because high forces act on the axis. Added to this is the heavy soiling to which the undercarriage components are exposed, depending on the surface," says Mr Roll. Another aspect: as the mobile machines work in the open air, lubricated linear axles were out of the question. Köppl therefore uses components from the igus® modular design system for various bearing solutions, including rotary ones. Typical for these components is the combination of high-performance polymers with incorporated lubricant (for the bearing) and hard-anodised aluminium (axis). "We use various igus® bearings and always receive good advice on them," says Benjamin Roll. This task is performed by igus® sales consultant Thomas Weber.

The axle displacement is now realised with a drylin® W-linear axis. Four carriages travel on the double rail profile guide, whereby the original design was adapted again. The complete igus® axis, including the housing for the carriage, was tested first. However, the four individual housings connected to the axis fastening with screws did not prove to be suitable. The forces were simply too high. The Köppl design engineers therefore decided, in consultation with igus®, to manufacture the housing themselves as a bar stock. It accommodates all four bearings, which are therefore in a fixed position in relation to each other. This eliminates the risk of individual profile guides twisting or jamming and the position of the axis cannot change automatically during operation.

The axis is adjusted hydraulically - and automatically if required. This option is recommended by Köppl because the operator can then concentrate on manoeuvring the machine (which can travel at astonishing speeds). In this case, an inclination sensor supplies the actual signal to the control system via CAN bus, and the axle position adapts to the current incline. This works over a wide working range and during operation. Benjamin Roll: "The Gekko works on inclines of up to 50.2o. This corresponds to a gradient or slope of 120 %." The principle of "the steeper, the more preload" then applies to the axle adjustment. When developing the Gekko and the axle adjustment, the designers already had the next step in mind. Karl Köppl: "We are working towards our machines being able to travel off-road autonomously in the future."

With the Gekko, Köppl has developed a truly high-end machine that is successful on the market, not least because of its adaptive axle adjustment. This is demonstrated, for example, by the current order from a regional road operator. Karl Köppl: "The customer invited tenders throughout Europe, tested them for two years and has now decided in favour of the Gekkos." Apart from this, users of a second series of single-axle machines can now also benefit from adaptive axle adjustment. The Taurus - a universal implement carrier for various mowers (in drum, portal, flail, disc and sickle design), soil, slot and stump grinders, mulchers and weed removers - is equipped with hydraulic axle adjustment, which the operator activates at the touch of a button and while driving. The adjustment travel here is 200 mm instead of 300 mm and drylin® W linear units from igus® are also used.