THE NEWEST GENERATION OF STRESS OPTIMIZED WHEELS FOR FREIGHT WAGONS

It is not easy to bring something new for seemingly simple wheels for freight wagons using brake blocks made from composite materials. Nevertheless, this simplicity is really only seeming.

The wheel must of course meet the legal requirements and standards. In EU, these are especially TSI?WAG, EN?13262:2023, EN?13979-1. Developing, approving and manufacturing a wheel with the typical diameter of 920?mm and with the required performance qualities is not such a big deal. It is much more difficult to design a wheel that will be in demand by customers for decades. This can be based only on decades of experience with manufacture, but more importantly with designing, approving and operating experience under varying conditions all over the world.

Wheels developed by BONATRANS GROUP a.s. , such as BONA324, BONA318 for the axle load 23.5?t, or BONA314, BONA319 for the axle load 25 t, have not only been in demand by customer but have also become a certain standard for all freight wagon types on the European market. Since 2017, they have been successfully followed by the BONA313 wheels. Many other wheels that appeared on the market have not stood the test of time. Some of them even came under the scrutiny of transport safety authorities.

So what is the difference? The answer is simple – the complex design that finds the ideal intersection between the requirements of standards on the one hand, and requirements of operators on the other. A brief recipe for an ideal wheel for freight wagons braked by composite brake blocks is as follows:

1.????? The wheel must not be too heavy so as not to increase the wagon weight and thus reduce the efficiency of transport, but also be sufficiently dimensioned so that the design can ensure the necessary heat removal from its tread during braking by composite brake blocks, as well as mechanical strength, including the fatigue strength.

2.????? The wheel must have low life cycle costs to bring costs savings. This means:

a)????? The highest possible durability even when composite brake blocks are used that cause higher wheel wear and increase the wagon operating costs by approximately 1?2?EUR/day compared to the previously used cast iron blocks,

b)???? Easy press-fitting on the axles, i.e. assembly of a new wheel, but also disassembly of the worn wheel without jamming, thanks to the optimized hub shape and parameters of the fitted joint.

3.????? The wheel should have a low carbon footprint, which is related to:

a)????? Production technology and wheel weight (the wheel should not be unnecessarily oversized),

b)???? Wheel operation – the longer the wheel service life, the lower the carbon footprint per unit of transport.

4.????? The wheel should have a low level of emitted rolling noise and thus create, together with composite brake blocks, basic conditions for “silent” freight wagons.

Each type of freight transport is specific, therefore requirements on the design of vehicles, including wheels, are also specific. For example, when transporting bulk materials such as aggregates, iron ore, etc., the aim of the designers is to reduce the weight of the vehicles as much as possible in order to increase the payload and to transport the load more efficiently. In the case of container wagons and swap body wagons, wheels that can cope well with higher dynamic forces are required due to often higher centre of gravity of these wagons with their loads. The load capacity of containers is limited by their design, so it is not necessary to have the lightest wheels, as in the case of bulk material, but wheels that will cope best with these specific dynamic load conditions related to the higher centre of gravity. And these are just two types of transport.

The place of operation brings other specific requirements for the wheels. The wheels will be stressed differently on mountain lines with small curve radii, differently on lines in flat countries in the part of Europe where freezing temperatures are very rare, etc.

Of course, each wheel must be able to be operated on any European railway line. It is similar with wheels for railway transport as with passenger car tyres. For example, no one will choose summer compound tyres for snowy winter roads, especially in the Nordic countries. Similarly, winter tyres for journeys in the sunny Mediterranean. Nevertheless, it can make sense for some motorists in some parts of Europe to use universal all-season tyres. We also keep these operators in mind.

That is why we offer several standardized freight wheel designs for various operational conditions to help the operators save costs and also reduce their carbon footprint.

This year, BONATRANS GROUP a.s. launches already the fourth generation of optimised wheels (with respect to their stresses and deformations). Following the third-generation BONA313 wheel that is the lightest wheel on the market and is designed for the axle loads of both 23.5?t and 25?t, we wanted to meet the needs of operators of modern container and pocket wagons, as well as swap body wagons, that are increasingly operated all over Europe, including mountain sections and Nordic countries. These wagons are often equipped with braking systems that allow them to be operated with wheels with the limit wear groove at the diameter of even 830?mm, compared to the common 840?mm.

Another modern wheel, BONA830EM, was thus created. This is already the fourth generation of stress optimised wheels from the BONATRANS design school for tread braked freight wagons.

It is a universally applicable wheel of a modern design for axle loads of both 23.5 t and 23 t. It is designed for extreme mechanical and thermal loading. It is therefore particularly suitable for the trans-European transport, container and pocket wagons, swap body wagons and other applications, such as operation in Nordic conditions and operation in mountain areas with frequent and intensive tread braking, frequent negotiation of curves with small radii, etc.

Thanks to the highest factor of safety in its class, the BONA830EM wheel can cope with what other wheels cannot. In addition, it brings savings to the operator thanks to its significantly extended service life.

“EM” in the name refers to Extended Mileage – higher mileage (service life) achieved thanks to the possibility to operate the wheel to the diameter of 830 mm and the enhanced BONASTAR?ER7 steel grade.

The number “830” in the name refers to the possibility to operate the wheel to the diameter of 830?mm (if the wagon design allows it) compared to the common 840 mm. This means at least 10% longer service life compared to wheels with the limit wear groove at the diameter of 840 mm.

The wheel service life is further extended by the use of the enhanced BONASTAR?ER7 steel grade that meets the requirements of TSI and EN 13262 and has substantially higher resistance to wear and damage due to rolling contact fatigue (RCF). Compared to the common ER7 steel grade, wheels from this enhanced steel grade achieve up to 30% longer service life.

For already operated wagons, where the existing design of the bogie (or the brake) does not allow the advantages of the 830 mm limit wear groove, a BONA830EM wheel version with the common 840 mm limit wear groove is approved.

Due to this, and also due to mutual interchangeability with other types of stress optimised wheels, it is possible to benefit from the high factor of safety and the extended service life of the BONA830EM wheel in virtually any newly manufactured or already operated wagon.

Within the ECO-design of the BONATRANS design school, we pay close attention to reducing wheel rolling noise. The wheel web shape was therefore also optimised to reduce rolling noise emissions.

Thanks to the modern design, the wheel has the highest factor of safety in its class, and yet its weight is 3 to 30 kg lower than other wheels on the market with similar use. ?The optimised weight increases transport efficiency and reduces energy intensity.

All BONATRANS GROUP a.s. wheels for freight wagons are mutually interchangeable within the given axle load (23.5?t or 25?t).

We are happy to help customers choose the optimum wheel for the concrete type of vehicle and transport.