The switchgear in electric trains must provide the forces to drive the train forward and to brake. Contact breakers in high-speed DC switchgear must, therefore, actuate many times per minute, and the kinetic forces involved in such actuations are significant. Insufficient absorption of shock can lead to contactors rebounding and reconnecting. This leads to inefficient motor operation and premature failure, with all the associated downtime and costs.
The challenge is to produce a composite damping block that includes a pad to absorb the shock and an impact surface with no tendency to stick, combined in a piece that could be securely mounted into a corrosion-free environment to prolong the maintenance-free life of the switchgear. These three properties are, at first glance, incompatible in a single component.
Each of the desired properties (shock absorption; impact resistance; secure, corrosion-free, mounting) is best achieved using a different material, and so the challenge was to combine these into a single product.
The successful product required the bonding of a Sorbothane block together with a stainless-steel backing plate and a PTFE impact face. It is difficult to think of three more dissimilar materials, and the bond strengths required, and achieved, are impressive.
Sorbothane is a proprietary material that combines superior shock absorption, good memory, vibration isolation and vibration damping characteristics and has a long fatigue life. It was therefore an ideal choice for this application. Our expertise in rubber-to-metal bonding meant that we were able to achieve the necessary bond strength between Sorbothane and the other materials.
The result is a composite damping block that at first glance seems impossible to make, but which was developed by our design engineers. It is in daily use throughout the world providing a cost-effective solution that keeps electric trains running.