"When a tree nursery transplants up to 1,000 trees each day, a root ball transplanter is always involved. The equipment must be rugged and reliable“, explains Roland Schlesag, General Manager at Optimal-Vertrieb Opitz GmbH, a family-owned business with 15 employees. "Our compact root ball transplanters are in use world-wide. “ We have been making these at our Thalmässing facility for almost 40 years. From A, as in Azerbaijan, to Z, as in Zambia, we make sure that trees are no longer tediously transplanted with time-consuming manual labor, but by machinery instead. "Our machines are extremely rugged", claims the General Manager. "For many years, this has been assured by maintenance-free polymer plain bearings. These are used in the hydraulic spade guides, various hinges and locks and also in the linkage between the primary and pivot arm. This allows us to guarantee low maintenance expenses and longer service intervals to our customers. “

The spades are pushed slowly into the soil. The polymer plain bearings are able to deal with dirt, moisture, etc.

Engineering and mobility

Dieter Opitz, the company's founder, set a milestone for the garden and landscaping industry by developing and producing modern technology for transplanting purposes. The machines were developed in the sixties and brought about enormous labor savings. Today, tree nurseries and landscaping businesses could not operate without these machines. Cleanly severed roots, tree conforming root ball shapes, gentle work in rows and reliable transportation: the tree transplanters ensure smooth and time saving operations at a very favorable cost/benefit ratio.

In addition to functionality, reliability and flexibility are among the crucial characteristics taken into account during the technical design phase. These are particularly compact machines that can be mounted on a variety of hauling equipment depending on need, and can be maintained with a minimum of effort. Even fully customized special purpose equipment is possible.

Today, an appropriate solution is available for any tree. The product range comprises twelve tree transplanters. They can dig root balls ranging in diameter from 36 cm to 2.50 m with a root ball depth from 30 cm to 1.50 m. Transplanting campaigns are generally scheduled for the spring and the fall. "When the season ends, the machine is normally cleaned with a steam jet and at best stored in a hall", Roland Schlesag states. "Since plain bearings are self-lubricating, the trouble spots will not incur storage damage due to the good dry-running properties. We rely on hard-chromed materials for the bolts. We believe that this is the ideal pairing that guarantees rugged machine engineering. “

Plain bearings for rotating and swivel movements

The ideal root ball transplanter will handle trees with considerable care. Their low working height permits trees to be removed without causing damage. The root ball matches the shape of the natural root growth. The favorable spade geometry and clean cut facilitates an accurate shape. The root ball stays intact, as it is fully enclosed by the spade. The low weight of the mounted equipment limits damage to the soil and roots.

Agricultural engineering requirements place particular emphasis on the absence of lubricants and long service life. Root ball transplanters place loads on iglide® G300 plain bearings primarily during swivel movements. In detail, this involves gimbal mounted hydraulic spade cylinders, as well as hinges and locks for the opening and closing frame components. On large machines that are mounted on trucks, plain bearings in the joints also ensure a secure connection of the primary arm with the swivel arm.

The highest loads are placed on the machine elements in the areas of the gimbal mounted spade cylinders when the four spades are steadily pushed into the soil with considerable force. A spade on one of the larger machines can theoretically push down with a force of 15 t. The means that a force of 150,000 N is applied by the hydraulics.

"We have had nothing but the best experience in this area with the plain bearings", states Reiner Irsigler in this regard. "They will hold up to the enormous surface pressures over time. This is in addition to their lack of lubricants, which is proving itself in daily use, whereas the soil permanently bonds to lubricated machine elements. Over time, the soil incrementally penetrates the bushings, creating friction and ultimately resulting in a failure."

The transplanting hole is also dug using the root ball transplanter.

The roots are cleanly severed when the root ball transplanter digs out the tree.

The root ball transplanter uses tribo-optimized cylindrical standard plain bearings made from iglide® G300 materials in a host of available dimensions. These are simply ordered from the catalog. The application spectrum is always the same on all machines, allowing the agricultural engineering firm to rely on standard solutions. "It simply works", comments Dirk Lanuschni, the responsible igus® sales consultant. "The iglide® G300 material is known as an all rounder. It comprises a broad spectrum of possible applications and is characterized by high wear-resistance and low friction values. “

This also includes another engineering detail that plays an important role and underscores the versatility of polymer plain bearings: "At some point the single-sided load will cause a red brass bushing to wear, which impacts tolerances. The clearance continues to increase until a bolt fails. Even though we used to use hardened bolts, for instance in the hinges, they still failed", the mechanical engineer recalls. "Bolt failures are now a thing of the past. The softer plastic material yields elastically, which completely avoids the notch damage that is the starting point for a failure. “

Heavy-duty applications for iglide® G300 plain bearings

In this application, the tribo-optimized iglide® G300 plain bearings demonstrate their versatility under the most adverse conditions. In spite of all adversities, they prove their long service life primarily in the hydraulic cylinders of the spades, when these are slowly pushed into the soil. "We provide engineering for professionals. Our objective is to produce quality made in Germany for our customer world-wide", Roland Schlesag confirms in conclusion. "And the maintenance-free and dry-running plain bearings have an important role to play in this. “

From left: Uwe Sund (igus® GmbH), Roland Schlesag (General Manager at Optimal-Vertrieb Opitz GmbH), Dirk Lanuschni (igus® GmbH), Reiner Irsigler (Mechanical Engineer at Optimal-Vertrieb Opitz GmbH).

3D rendition of the guide box: a host of applications for polymer plain bearings.