Instead of expensive track systems the technically mature drive solution for harvesting machines: NAF's bogie axle combined with the directly driven steering axle with adjustable track width


New system from NAF

For nearly 60 years NAF AG – Neunkirchener Achsenfabrik AG located in Neunkirchen a. B./Germany– has been a specialist in high performance drivelines for construction, forestry, agricultural, materials handling and mining machines, working in the World’s toughest ground and climatic conditions. 

Experience and advanced technical ability have made the company one of the World market leaders in bogie axles for more than 30 years. NAF AG introduced its front bogie axle drive system for ag machines which is a superior and cost efficient drive solution, compared to expensive track systems as front and rear drivelines.

The oscillating bogie halves - one on each side of the vehicle - derive from NAF’ long term experience in forestry and construction applications. They are equipped with NAF’ integrated Permanent Bogie Balancing System (PBBS®) that insures an equal distribution of weight and tractive effort on all four tires. The patented PBBS® derives from forestry bogie axles as well. It works with a special gear set inside the bogie that reduces the lifting effect of the bogie front wheels thus providing outstanding off-road capabilities, superior stability and tractive effort. It is a proven pure mechanical system which acts independently and autonomously from the driver: it automatically acts when the bogie front ends are lifted during acceleration or while climbing slopes. This all results in lower ground pressure with lower soil compaction compared to track systems, all presented in diverse academic publications e.g. “Combine with 3 axles –soil friendly and energy efficient” by Döll, Herlitzius, Bilde Technical University Dresden and “Soil compaction: track induced soil stress isn't so positive in comparison with tires” by Miclet, Piron, Pinet (VDI Tagungsband 2193).

Utilizing NAF‘s modular system, the bogie axle system can be adapted to every application. The ag bogies share the same components with axles for forestry and construction machines, providing customized products, optimized for ag application but based on cost-efficient, highly standardized modules such as planetary hubs, differentials and hydrostatic drives. The system includes high capacity and self-cooling oil immersed disc brakes integrated in the planetary drives, while a tire pressure control system is available on demand.

In terms of daily usage the bogie axle gets ahead of track system by far better maneuverability and less shear forces on ground during turns. Additionally a so called bogie lift system can be installed which allows to lift the front tires and the machine is solely driving on the rear tires of the bogie axle resulting in better performance and less wear and tear during road travels. In general high travel speeds up to 50kph are realized with smooth riding combined with low maintenance costs. Besides its practical advantages the bogie system is also convincing with moderate system expenses combined with low lifecycle costs.

To complete the vehicle’s driveline in agricultural harvesting machines, NAF also offers centrally driven rear steering axles with adjustable track width to adapt to different tire sizes. On the rear adjustable driven axle, the width can be adjusted in two, three or four steps, for example for 200 or 400 mm, depending on the application and tire usage. This axle family covers combine harvesters size 6 to 10, which means a rear axle load from 9 to 14 tons.

With this solution the tractive effort of the centrally driven system is nearly double in comparison to legacy systems using two wheel-mounted hydraulic motors. Also one central hydraulic motor leads to and easy and simplified hydraulic control and regulation system, also not to forget the cost advantages to legacy systems. NAF uses various hydraulic motor suppliers, also depending on the harvester size; typically in the size between 80 and 150 cm³. The design with one central hydraulic motor also offers the advantage of being lighter.

Source: Diesel Progress International - Sept./Okt. 2019