dryspin® lead screw drives keep gap bridging moving on trains

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 functionality despite high temperature fluctuations and a wide range of dirt
• Low life cycle costs due to freedom from maintenance
• Completely lubrication-free

How the sliding step works

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. In addition, the cost-effective plain bearings made of the universal material iglidur G are used. They are maintenance-free, abrasion-resistant and, like the other components, insensitive to dust, dirt, moisture and cleaning chemicals.

More than three million cycles in the test

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 in production is reduced. High helix lead screw and high helix lead screw nut can be easily changed on site by the customer and installed effortlessly. 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 worst thing that will happen to an igus lead screw nut is more clearance. It is a slow process that announces itself and can be eliminated promptly. For gap bridging, two test series are currently in progress at the location in Austria. 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.

System in plan for arctic temperatures

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.

dryspin® lead screws
made of stainless steel

► To the online shop

Lead screw nuts
made of iglidur® J

► To the online shop

Order online:

Configure lead screw drive:

Improve technology ... reduce costs: