Combination of Low-wear in Curves and Running Stability now Possible
2010.02.01
Hydraulic axle-guide bearings drastically reduce maintenance costs for rail vehicles
With the newly developed hydraulic axle-guide bearing known as HALL, the vibration-control technology specialists in the company Freudenberg Schwab GmbH have succeeded in simultaneously optimizing the driving performance of rail vehicles on the straight and in curves. Thanks to HALL, manufacturers and operators of rail chassis and bogies are now a considerable step closer to a universal solution for low-wear, quiet running properties in curves and high running stability on the straight. Another outstanding advantage of this innovative product is that existing rail vehicles can easily be retrofitted with HALL.
It is a well-known fact that radially adjustable wheelsets are the prerequisite for low-wear, low-noise running in curves in all rail vehicles. A reduction in the striking angle of the wheels on the track reduces the forces between the wheel and the track, thereby minimizing the wear of both components considerably. In order to allow for the adjustment of the wheels when the vehicle is taking a curve, the axle-guide bearing must have the lowest possible level of longitudinal stiffness. On the other hand, the axle-guide bearing has to be very stiff in order to ensure that the vehicle runs smoothly on the straight, in particular at high speeds.
These conflicting demands on the axle-guide bearing have led to compromise solutions being used in the past. With the hydraulic axle-guide bearing (HALL), it is now possible to combine the low longitudinal stiffness needed for curves with the high longitudinal stiffness required for the straight in a single component.
Fascinating technology that squares the circle
The apparatus that has been integrated into HALL generates frequency-dependent changes in longitudinal stiffness. This means that the hydraulic axle-guide bearing can be designed in such a way that a low level of stiffness is automatically ensured in the event of the low-frequency excitation of vibrations, i.e. when the rail vehicle enters and exits a curve. In other words, HALL allows wheelsets to be adjusted to suit the curve.
In the event of excitation frequencies of above 2–3 Hz, i.e. in the event of dynamic excitation at higher speeds, the bearing stiffness rises progressively to ensure optimized dynamics of rail vehicle movement. Conventional bearings have a longitudinal stiffness between 6 and 40 kN/mm. HALL, on the other hand, has a longitudinal stiffness of only 6.9 to 7.4 kN/mm in the slow deformation range. This rises progressively to between 28.5 and 31 kN/mm when the vehicle moves faster. Other versions have an even wider range of between 3.5 kN/mm and 34 kN/mm. In this way, HALL automatically and optimally adapts the longitudinal stiffness of the train chassis to meet the requirements of taking a curve and the dynamics of traveling at high speeds. The design of HALL is such that the adaptable range of stiffness can be adjusted very accurately to meet requirements. The transverse stiffness of conventional bearings and HALL are quite similar.
Incredible benefits for operators
Thanks to HALL, the stiffness of the axle guide in the longitudinal is always automatically optimized. The longitudinal stiffness is low (soft) when taking a curve (which reduces wear on the track) and high (hard) for high-speed travel. This means that HALL has a number of benefits for the operator:
• extended wheelset service life, which means
• fewer inspections and lower inspection costs, and
• extended track lifetime, which means
• lower wear-related rail track fees.
This means that HALL reduces maintenance costs for rail vehicles and networks dramatically. The reduction in the life-cycle costs (LCC) of the wheelsets and tracks in particular is massive.
After five years of successful field operational tests and comprehensive test bench trials, HALL is now being tested in further operational trials so that it can go into serial use in 2010. For these trials, the component will be tested in vehicles taking curves and in stability tests. The results will then be compared with conventional bearings. Because HALL fits seamlessly into existing bearing installation spaces and can be used to replace existing axle-guide bearings, operators can benefit from it very quickly indeed. Economic efficiency analyses show that in Great Britain, for example, the cost of HALL can be redeemed in a short space of time because of the resulting reduction in rail track fees, which are calculated on the basis of wear caused and longitudinal stiffness.
The considerable interest shown by operators and systems retailers in HALL in Europe once again proves to Freudenberg Schwab GmbH and Schwab Schwingungstechnik AG that it is on the right track with its technical development work and ability to produce innovative products.
Comprehensive range of products now includes pneumatic springs
In addition to the innovative HALL, Freudenberg Schwab GmbH has also added air suspension systems to its range of products. As the secondary suspension level, the air suspension system links the chassis to the body and makes a vital contribution to the safety, comfort, and smooth running of the vehicle.
The combination of Freudenberg Schwab’s specialist know-how, backed up by the Freudenberg group’s comprehensive expertise in the production of pneumatic springs is a pledge for the success of this move. After all, through its subsidiary VIBRACOUSTIC, Freudenberg has for some time been one of the market leaders in the field of pneumatic springs for passenger cars and commercial vehicles.
Naturally, in addition to HALL and the air suspension system, Freudenberg Schwab also provides other rubber/metal parts for rail vehicles. This means that primary and secondary suspension, axle guides, elastic drive couplings, torque supports, anti-roll bars, aggregate bearings, and carriage couplings can all be obtained from a single source.
Illustration
The innovative hydraulic axle-guide bearing (HALL) fits into existing installation spaces. It automatically ensures optimum longitudinal stiffness in the axle guide. The longitudinal stiffness is low (soft) when taking a curve (which reduces wear on the track) and high (hard) for high-speed travel. In this way, HALL dramatically reduces maintenance costs.
Freudenberg Schwab GmbH
Henrik M. Egeter
- Managing Director Sales -
Postplatz 3
D - 16761 Hennigsdorf
Germany
Tel.: +49 (0) 3302 2062 0
Fax: +49 (0) 3302 2062 77
e-.mail: henrik.egeter@freudenberg-schwab.de
http: www.freudenberg-schwab.de
