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The science of silence

The issue of noise and vibration in the interaction between track and vehicles on light rail and metro systems is a major challenge for both authorities and operators.

We’ve already discussed industry best practice on what can be done to minimise the effects in terms of both new and existing infrastructure (TAUT 966). This time, Marcel Ujfaluši, Head of Business Development and Marketing for GHH-BONATRANS, looks at how the company’s innovations are helping vehicle manufactuers and maintainers address this serious issue to deliver a smooth, quiet and comfortable ride for passengers.

Q. What are your recent innovations for the tramway and LRT market?

A. We are not just a wheelset manufacturer. Our recent supplies of innovative products are based on many years of in-house research and development.

For example, Modertrans is currently using our products for the new fleet of trams it is supplying to the Polish city of Poznań. This includes 50 uni-directional five-section 100% low-floor Gamma trams. The wheelset design for this vehicle is characterised by several innovative features. Increased fatigue strength of the BONAXLE – an induction hardened axle – has enabled the creation of a lightweight design, while a higher degree of hardness of the axle seat virtually eliminates the possibility of wheel centre seizure during assembly or disassembly.

The trams’ resilient wheels are based on the traditional BONATRANS design school, with special longitudinal pins on the outer wheel centre circumference that increase the resistance to rotation of the wheel centre relative to the tyre. The new tyre has a diameter of 610mm and is manufactured from P70 grade material, the hardness of which is at least 45 HB higher than the hardest grade according to the European standards (ER9).

The weight of this resilient wheel is less than 220kg and it is designed for an axle load of 8t. The wheel also includes the BONASILENCE D noise absorber mounted on its outer side; this can reduce the rolling noise level by up to 7dB, and the squealing noise during curve negotiation by up to 30dB. These innovations all work together to deliver a quieter and more comfortable ride for passengers as well as giving a longer-lasting product for operators.

Q. Can BONASILENCE be tailored to suit different requirements?

A. Yes, indeed. We design, manufacture and supply complete systems specifically aimed at different rail segments (urban, suburban and inter-city and freight). All of these solutions for noise mitigation fall under the umbrella trademark of BONASILENCE.

Over the last 20 years we have developed four main types of wheel damper: BONASILENCE P, BONASILENCE D and BONASILENCE M all combine metal and rubber and are chosen and tuned depending on the noise limits as specified by the customer. BONASILENCE R is based upon a stainless steel ring and is suitable for wheels braked by blocks. In terms of initial costs, it is the least expensive measurement.

The lifetime of the first three, more sophisticated, solutions is at least 15 years, so exceeds the lifespan of one or more wheels (or tyres in the case of rubber sprung resilient wheels). Also, due to their easy replacement, dismantling of whole wheelsets from the vehicle is not required.

Q. What kind of noise reduction levels can you achieve?

A. BONASILENCE® is able to reduce squealing in curves (where the wheel is the dominant source of noise) by up to 30 dB(A) in the frequency band where squealing is significant. It can also reduce the rolling noise of wheels by up to 10 dB(A).

One should not forget that there are several types of noise emission that occur during operation, including rolling, squealing, braking and aerodynamic. Although dampers significantly reduce the wheels’ rolling noise, the overall noise is also caused by track conditions and the whole vehicle. Without any joint effort of damping other elements, on its own BONASILENCE can reduce noise by up to 3 dB(A) for the position of the microphone according to the Technical Specifications for Interoperability (TSI) which are 7.5m from the centre of the track at the height of 1.2m above the top of the rail.

Of course the acceptable limits vary, these usually come from the vehicle manufacturer in the case of new rolling stock, or from operator in the case of existing fleets. In either case, once we integrate noise mitigation into wheel design, the solution is always more efficient and/or less costly over the product’s lifecycle.

Q. What feedback have you received from cities using BONASILENCE?

A. Since 2005 we have supplied approximately 100 000 wheels across the four types of noise dampers mentioned earlier, or their combinations, and mounted on resilient wheels as well as on steel monoblocks.

They have seen successful service in metro cars and on tramways around the world, including those in Toronto, Boston, Oslo, Prague, Athens, Helsinki, St Petersburg and Hong Kong, as well as in inter-city Pendolino trains in Finland and the Czech Republic, to name just a few.

 

Article originally appeared in TAUT 971 (Nov 2018).