Find out how to choose a double wheel for tractors

When purchasing a double wheelset for your tractor, it is necessary to take into account several factors that will directly influence the choice of model, ensuring an ideal combination for each type of tractor and activity you will carry out.

The incorporation of a second set of pneumatic wheelsets into the wheelset system of agricultural tractors or harvesters has recently become common in agricultural companies. This practice has technical support in improving the tire (machine) – ground relationship, the interface of the two bodies. In other words, based on the possible benefits to the characteristics of the soil and the efficiency of operations with motorized sets, assuming that the primary functions of the wheelsets are support, support and carrying out traction effort.

In this way, with the use of an extra wheelset per semi-axle of the tractor, there will be a greater contact area between the machine and the ground, representing greater support, better distribution of the tractor's mass, less pressure exerted on the ground, ensuring better performance in terms of traction. for presenting better tractive performance. However, depending on the type of work surface, inflation pressure and tire diameter, efficiency will not differ much from that of a tractor with a single wheel and, consequently, greater power availability at the drawbar. In this case, it is necessary to clearly define the objectives of using double wheels to verify economic viability. Depending on the characteristics of the operations to be carried out, the cost/benefit ratio will be irrelevant.

The addition of the extra wheelset is associated with the size of the tractor, that is, depending on the engine power and tractor performance, with main use on large tractors, with engines above 149kW. But this does not exclude the dual configuration on smaller tractors with power below 149kW, as long as technical and economic feasibility is proven.

When purchasing a new tractor, the double wheel configuration is an accessory, the choice being up to the customer, but there is availability on the market of specific coupling kits sold by specialized companies and certified by the manufacturers, at an attractive cost.

COUPLING SYSTEMS

From an engineering point of view regarding coupling, there are different systems to turn a tractor with a single wheel into a double one, as highlighted below.

One of the systems is the one that attaches the extension hub directly to the rim of the inner and outer wheelsets, which will be the link between the two wheelsets. The drawbacks of this system are the difficulty in installation and the long time for assembly and disassembly due to the need for alignment with the internal wheel and the number of screws that must be tightened to fix the hub.

The second option is to add the extra wheelset to the tractor's own semi-axle, this is an extended axle, generally available by manufacturers on tractors above 149kw. As with the previous system, there are the same difficulties in terms of practicality and installation time, however it offers the advantage of greater flexibility in terms of changing the spacing between the wheels, as they can be moved on the bar.

Finally, a system using a spacer ring inserted between the internal and external wheelsets adjusted to the base of the rims and the fixation is done by clamps, recommended for tractors with power below 149kw, although there is availability on the international market for tractors above this power. . There are several mechanical configurations of this system on the national and international market, with the aim of facilitating and saving time in assembly and disassembly. The great advantage is the ease of assembly in less time and the possibility of adjusting the spacing for use between rows of annual crops such as corn, soybeans, cotton and others.

DIFFERENT OPERATIONS

All three coupling systems can be used in any type of operation, so the definition of the most suitable one must take into account the characteristics of the activities to be carried out, the topography of the property and the crops exploited. In areas with greater slopes, characteristic of mountains, with slopes, where exploration takes place over long periods and requires greater stability in operations, you can opt for the extension hub and tractor axle systems, as there is no need to disassemble.

In farm systems where different operations are carried out – cultivation, application of fertilizers and pesticides – when sometimes you need more stability for the tractor or even to avoid damage to the soil structure and sometimes there is no need to use it, you can opt for quick coupling system, due to practicality and less time spent dismantling. On some smaller properties, the total width of the tractor with double wheels sometimes becomes limiting due to narrow carriers and gates, where quick disassembly makes logistics easier.

One of the main disadvantages of purchasing a double wheelset is the acquisition and maintenance cost. Another important point is that the addition of a wheelset on each side of the tractor will increase its width, making it difficult to transport on public roads and access roads to activities, requiring adaptations throughout the area. Different activities carried out during the same work period that require the assembly or disassembly of the double wheelset result in a considerable loss of time, a limiting factor in periods of high activity. Furthermore, if the first wheel on the axle has a hole, the second wheel will need to be removed to carry out the repair.

With the presence of double wheels, some parts of the tractor such as transmission and axles can become too heavy, causing premature wear of these parts and future problems with the machine.

COUPLING SYSTEM OPTIONS

There are two companies on the national market providing double wheel adapter services in the country, Marini and Techonoradas, both with manufacturing facilities installed in Rio Grande do Sul.

The company Marini offers the most used systems for coupling wheelsets, with emphasis on the quick-coupling coupling system that facilitates the daily movement of changing between single and double wheelsets.

Technorodas presents a differentiated range for adaptation to double wheelsets and the highlight is the multipurpose stretcher-separator with specific adjustment for external wheels.

In general, a better performance of the tractor was proven in relation to traction, specific fuel consumption, power available on the drawbar, as well as the increase in contact area and the lower pressure exerted on the ground, but there is no difference significant.

The performance of tractors with single or double wheels is influenced by the tire inflation pressure, depending on the choice, better performance may occur with the single wheels. Regarding the operational capacity that can be influenced by the slipping of the wheelsets, there was no difference between single and double wheelsets.

Some results of a survey carried out by specialist Ulisses Giacomini Frantz, Federal University of Santa Maria, highlight the better performance of the tractor and the effect on the ground of the double wheel system compared to the single one. Table 1 presents approximate data, taking into account the same inflation pressure.

The closing thought

The facts mentioned are extremely important for making decisions about whether or not to use a double wheel. It is essential to define the objectives of using the double wheelset, as well as survey all the characteristics of the production system to ensure the correct choice. As it is not a low-cost system to install, it is essential to determine the return on investment.

What to consider when choosing a double wheelset?

When choosing a double wheelset, it is necessary to clearly define the objectives regarding its use, taking into account the possibilities of application in different operations, soil conditions, topography and crops, minimization of negative effects on the soil, stability in rugged areas, improvement of traction depending on the type of soil and management.

Other important factors:

- Quick assembly using a coupling system with as few fixing points as possible.

- Ease of coupling without the need for alignment with the internal wheel depending on the type of attachment.

- Possibility of application on wheels from 8” to 54”.

- Compatibility with any brand and model of tractor.

- Availability of kits for tractors regardless of power with an easy and quick coupling system.

- Application of double wheelsets on the front of the tractor.

- Kit acquisition and maintenance costs versus possible applications and definition of benefits that justify the investment.

- Possibility of suitability for use between rows of annual crops at different spacings. 

Marcos Roberto da Silva, Edeilton Arruda dos Santos, Fabrício Pedreira Santos, Ismael dos Reis Alves, Federal University of Recôncavo da Bahia; Avelar Araujo Alves, Raphael Moraes Pinheiro, Riagro

Article published in issue 157 of Cultivar Máquinas.