The sliding steps are used in trams, suburban and underground trains, in regional trains as well as high-speed trains. Two versions were developed with an eye to necessitating as few major adjustments as possible. With an installation height of only 50 millimetres for sliding steps up to 1,400 millimetres wide and 350 millimetres extension width in the standard version, they are very impressive on the market. The extension width of the sliding step depends on the infrastructure of each station. In addition to the standard solution, a second version with a longer extension width is being developed.
The requirement profile of the railway builder and rail operator is as follows:
► Flawless function despite large temperature fluctuations and a wide variety of contamination
► No maintenance required, resulting in low life cycle costs
► Entirely free of lubrication
The sliding step is moved via the central lead screw drive with clamping-free guide system. The locking module is also completely free of maintenance and adjustment. The lead screw holds the sliding step in every position. They must be able to withstand heavy steps or sweeping movements all the time. But there are more adversities. If there is a power failure, the running board can be retracted manually. Then the lead screw has to work in reverse without jamming.
The high helix lead screw, which is used in the non-hermetically sealed sliding step, is lubrication-free and therefore maintenance-free. It achieves higher efficiency through a flatter thread angle. An asymmetric geometry between lead screw and nut increases the service life. Rounded tooth flanks ensure better running performance as well as quiet vibration-free running. The associated dryspin flanged lead screw nut made of iglidur J ensures virtually no wear for high efficiency. The dry operation ensures that nothing sticks on. The special sliding block - also made of iglidur J - absorbs the forces when the lead screw or the sliding step drives out. There are also cost-effective plain bearing bushings made of the iglidur® G universal material. Used in the locking system, they are maintenance-free, abrasion-resistant and, like the other components, insensitive to dust, dirt, moisture and cleaning chemicals.
In order to allow an easy installation and maintenance of the new sliding step, special emphasis has been placed on adjustment-free solutions in the design. All pre-settings are made at the factory and a later component replacement requires no adjustment. Another advantage is that the complexity decreases in the production. High helix lead screw and high helix lead screw nut can be easily changed on site by the customer and easily installed.
The solution from igus is also advantageous in terms of durability. In the worst case, a belt drive tear could result in train failure. But the worse thing that will happen to an igus® lead screw nut is more clearance. And that is a slow process with many noticeable signs, so it can be corrected in time.
Two gap bridging test series ran at the Austria location. On the one hand, in a worst-case test, the running board runs against an obstacle - usually the platform. We ran a million cycles simulating such an error and saw no failures. In normal operation, everything worked flawlessly after 3.5 million test cycles. Find out more about dryspin® technology test reports here.
The two sliding steps with the two lead screw lengths are used primarily in temperate climate zones. They are designed for temperatures down to -25°C. Systems for temperature ranges down to -40°C are currently in the planning phase. The igus laboratory is already running test series for material developments for permanently low temperature ranges in order to provide an optimal quality solution.
A train has a service life of at least 40 years. Individual coaches can be used for up to 60 years. The first main maintenance with replacement of components usually happens after 15 years. Safety checks are made every three months. The sliding step itself is cleaned only twice a year. These figures illustrate how robust, reliable, and durable the components must be. They have to work not only in the lab, but above all, in the field.
Our expert, Thorben Hendricks, will answer all your questions about drylin® lead screw technology. Just fill out the contact form, and we will address your concerns. We look forward to your message.
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Product Manager for iglidur® Bearings ASEAN
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