"We produce approximately 450 tank trucks per year," reports Sebastian Zunhammer, the managing director of the family-run company Zunhammer GmbH. Around 100 people are employed at the factory in Matzing-Biebing near Traunreut. In one- and two-shift operations they exclusively produce customized vehicles. "Be it tires, distribution or docking systems, pumps or working widths – as a rule these are customized solutions that are completely manufactured in our factory. “

All components of a liquid manure barrel are compatible. This applies to the tires, the tank and the pump, and also to the undercarriage. The carriage is decisive in the handling and traffic safety of the liquid manure tank truck. "We place great emphasis on quality and comfort," says Sebastian Zunhammer.

In total, four tribilogically optimized iglidur® Q polymer plain bearings with a diameter of 80 mm are used in the pendular trapezoidal axle.

The Zunhammer GmbH was founded in 1956. Initially a cooperage, it later became a company for vehicle construction. In 1958 the first liquid manure tank truck with a wooden barrel was produced. The first patent protection of a utility model was obtained in 1959 for a centrifugal barrel truck with 2500 liters, which at that time was still made of wood. Carriages are built here since 1962. To be able to equip larger tank trucks with tires, an independent tandem axle was developed. "Since the end of the 1960s we've been producing pendular axles, which later became steered pendular axles," tells Zunhammer. Today, for us, the pendular trapezoidal axles are the latest in vehicles. “

Managing director Zunhammer is a wood technology engineer, but realized early on that plastic is the material of the future. As a result, the liquid manure barrels switched from wooden tanks to glass fibre-reinforced polyester tanks. This saved a lot of weight, but gave the same stability and very good flow-out characteristics. The containers today reach sizes up to 27,000 liters. The automatic nutrient analysis shows what such a modern liquid manure tank truck can perform. The detection of nutrients is done from a liquid manure pipe by an NIR sensor, which continually taps information about the liquid manure consistency. In this way the liquid manure can be examined during filling, spreading and mixing. It is not only nitrogen (N) which is recorded thus, but also potash (K), phosphate (P) or the dry mass (TM). It is also possible to register additional substances. The system is as progressive as modern manuring with minerals – which it can completely replace – and unique worldwide in liquid manuring. "Accordingly our customer base reaches far beyond Germany's borders," the MD Zunhammer explains.

Initially brass bushings were used in the pendular and/or steered pendular axles. But in the long term these could not prove their worth. Because, with regard to liquid manure transport and liquid manuring a lot of dirt and dust accrues from roads and fields, which accummulates everywhere.

The wear of the brass bushings was too high. "Therefore we were glad when the polymer bearings finally offered an effective alternative," remembers Sebastian Zunhammer. "As the plastic bearings are simply more rugged." Normally, though, the bearings in the axles are not in direct contact with the liquid manure. But during distribution the spray is pretty fierce, so that accumulating residue cannot be immediately removed.

Tribo-optimized polymer plain bearings made of the iglidur® Q material have been proving their strength in the steering arm of the tandem axle since 1996. For additional protection thrust washers, also made of iglidur® Q, are used.
"The rotation of the steering is low, but the surface pressure is very high," design engineer Thomas Bauer explains the technical requirements. Bauer is also responsible for the in-house organization and quality assurance in the company. The plastic plain bearings are highly abrasion-resistant with extreme loads and insensitive to edge loads and dirt. "After the lubricant-free bearings came to be used, failures haven't occurred anymore. In addition liquid manure is very aggressive. There is always an ammonia cloud hovering around the vehicles which also affects all components. "The plastic components, particularly the axles, have to work in all conditions," explains Thomas Bauer. Particularly because economical aspects too have to be taken into account. Agriculture depends on the weather. One cannot go out on the field in any weather. Besides, the vegetation has to be right while distributing the liquid manure. So it's no wonder that a liquid manure tank truck is in operation only for a maximum of 100 days per year. "During this period the performance must be good," explains Sebastian Zunhammer The distribution of liquid manure is often carried out by contractors today. "In the high season they are at times in operation 24 hours, seven days a week. During that time no technical failure must occur." “