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Bearings for agricultural machinery

Bearings for agricultural machinery

The advantages of application-specific special bearings When the going gets tough:

Heavy mechanical stress and abrasive particles in the operating environment: bearings for agricultural machinery have to operate under conditions that are anything but ideal. However, there are bearings that have been specially developed for agricultural machinery and attachments. Joint development projects between bearing and machinery manufacturers focus on reliable seals and component integration.

A look at a specific agricultural implement illustrates the requirements for bearing units in agricultural machinery. Harrows are used to prepare the soil for seeding. They have disc-shaped attachments that run through the soil and thoroughly mix the top layer to create an even seedbed. The discs must rotate regardless of the terrain, so smoothness is an important criterion.

Tailor-made angular contact ball bearings for compact disc harrows.

It should come as no surprise that the environmental conditions for the bearings in the individual discs are anything but favorable. The harrows operate in dirty, dusty environments, so the sealing of the bearings must be very effective. They also travel at speeds of 10 to 15 km/h over uneven ground and must withstand impacts from stones in the soil.

This design has several advantages, such as a much higher working speed, which is why farmers prefer the individual disc suspension on so-called compact disc harrows. However, the individual discs are subjected to high axial forces, which the bearings have to absorb.

The latest trend: component integration

A leading harrow manufacturer asked for the development of a customized design to ensure particularly durable bearings under these harsh conditions. The company’s designers chose a double-row angular contact ball bearing with a split inner ring, whose design allows it to support high axial and tilting forces. Easy mounting: an important aspect

The bearing is housed in a ready-to-install housing unit, also supplied by the company. This forms the entire unit between the disc and the bracket. On the disc side, the bearing units are fixed by a flange with five screws. The inner rings of the bearings are connected to the axle, which is inserted into the mount and fastened to the disc carrier with a nut.

Maintenance-free design with lifetime lubrication

A highly effective seal is one of the most important requirements for this bearing unit. A static seal is used on the disc side. On the other side, there is a static seal next to the bearing unit and a dynamic seal with two sealing lips between the bearing unit and the disc carrier. This sealing system has proven itself even in the presence of extreme dirt, moisture, and abrasive or corrosive soil constituents such as sand and fertilizer.

Although subjected to immense stress, the bearings are maintenance-free and do not require relubrication. The housing is filled with a special high-performance grease that can absorb a great deal of pressure and remains effective over the entire life of the bearing. This eliminates the need for relubrication that would otherwise be required. This not only saves time and grease but also protects the environment, as no lubricant can escape from the bearing unit.

Flanged bearings for combined cultivators and seed drills

Once the soil has been prepared, the seed is spread. As in many sectors, the trend in agriculture is toward increasing mechanization and automation. So it’s only logical that manufacturers are trying to combine several work steps in agriculture. One attachment manufacturer has succeeded in this by developing an innovative machine that works the soil and sows at the same time.

Here, too, a lot of dust accumulates and the components are subjected to high mechanical stress. The company has also developed a flanged bearing unit for this application. In this unit, the seal is supported by an upstream flinger disc. A close-fitting three-piece seal provides an effective barrier in the adverse conditions in which this machine operates. Like the custom harrow bearing, this one comes with a maximum grease pack to eliminate the need for relubrication and provide a lifetime of lubrication.

The combination of the centrifugal washer and three-piece seal provides long life in very dusty conditions. In addition, the company was able to increase the load rating by 30% compared to the previously used bearing unit.

Pulleys for rotary rakes

A manufacturer of attachments for agricultural machinery was working on the development of a new series of rotary rakes used to collect crops such as hay and straw. Initial tests showed that the new series’ pulleys soon failed.

The original pulleys were designed like a pair of single-row angular contact ball bearings with a reinforced outer ring. After a thorough analysis of the operating conditions, the company suggested using pulleys with reinforced outer rings and a special seal.

The lubricant also had to be optimized. Instead of standard grease, a specially developed MA7 grease is used, which extends bearing life in adverse environments by about 10%. The company was soon able to supply the first samples. The test phase was absolutely satisfactory so that the manufacturer released the prototypes for series production after only six weeks.

Asymmetrical double tapered roller bearings for tractor transmissions

The company has not only developed customized bearings for agricultural implements. It has also developed units for tractor drivelines. Here’s an example. For a tractor transmission, the company designed a special bearing. Consisting of a double tapered roller bearing with an asymmetrical cage. One of the two tapered roller bearing rows was given longer rollers so that it could support very high loads. For the other row, a shorter roller design was chosen to minimize friction losses and thus energy waste.

This results in an optimum compromise between the two development goals of energy efficiency and the absorption of high loads. A spacer ensures that the clearance between the two inner rings does not exceed the desired tolerance range. And also prevents corrosion in this critical area.

Conclusion: Alternatives to the standard range

The examples show that agricultural machinery places above-average demands on bearings and pulleys, as they often operate under adverse conditions and heavy mechanical loads. It therefore often makes sense to use customized bearings, e.g. with improved seals (triple lip seals, centrifugal pulleys).

The user benefits from longer bearing lives, while the equipment manufacturer often achieves additional functionality with these bearings. And can facilitate installation, e.g. by using installation units and flange bearings.

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