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Top of Rail Friction Management Explained

RS Clare & Co.

If you’ve heard of Top of Rail Friction Management but are still not sure what it is, this post is for you. A short introductory guide to the topic, it will tell you all you need to know about the basics of this exciting area of wheel/rail interface friction management.
By Richard Williams, Area Sales Manager Rail


What is Top of Rail Friction Management?

Top of Rail Friction Management is a means of controlling railhead coefficient of friction through application of a specially designed friction control material. This material, which is not a lubricant, creates a film on the track which acts as a “3rd layer” between wheel and rail surfaces to ensure the optimum coefficient of friction at the rail crown and wheel tread interface is maintained.

 

What are the benefits?

Applied to the top of the rail, a Top of Rail Friction Control Material reduces wear – extending rail and wheel life and lowering long-term maintenance costs. By reducing the friction coefficient at the rail crown and wheel tread interface compared to dry conditions it can also lower fuel or power consumption.

Effects of Top of Rail Friction Management Benefits of Top of Rail Friction Management
·       Optimum friction coefficient

·       Reduced rail and wheel wear

·       Reduced rail contact fatigue

·       Prevention of corrugation

·       Reduced hunting (lateral oscillation on tangent track)

  • Improved fuel/energy efficiency
  • Lower maintenance costs
  • Longer service life
  • Reduced risk of derailment
  • Lower noise and vibration, including flanging noise, curve squel and rolling noise

 

What is the coefficient of friction? And why is it important?

The coefficient of friction is a measure of the friction that exists between two surfaces. If the coefficient value is zero, then there is no friction. (This is very uncommon, as nearly all surfaces produce some friction when moved against each other.) We use the coefficient of friction to calculate the resistance between the rail track and train wheels.

Trains need a certain amount of friction to operate. If there was no or very little friction, the wheels would gain no traction and would simply spin in place. On the other hand, if there is too much friction, more power is required to move the train, leading to increased fuel consumption. Too much friction also causes rail damage, such as rolling contact fatigue and corrugation, and track noise.

 

What is the optimum coefficient of friction on a rail track?

On a train track, the coefficient of friction is influenced by several factors, including interface geometry and the surface properties of the wheel and rail (i.e. roughness, hardness and temperature). The coefficient of friction can therefore be variable depending on the track, wheel and environmental conditions such as moisture or humidity.

The aim for rail operators is to reduce the coefficient of friction to a safe intermediate level that allows normal traction and braking, and which remains stable under all normal operating conditions. At the wheel/rail interface, this is usually within the 0.3-0.4 range. On a dry unlubricated rail, it is around 0.7.

 

What are the necessary properties of a Top of Rail Friction Control Material?

The ideal Top of Rail Friction Control Material is formulated to consistently provide the optimum friction coefficient at the wheel/rail interface, in both dry and wet conditions and across a wide temperature range.

As a Top of Rail Friction Control Material can be applied all year round, it should be easy to apply in all conditions, including summer and winter months. It should also be ‘readily biodegradable’ (i.e. it should contain no solvents, micro-plastics, latex, or toxic materials) so it doesn’t negatively impact the environment.

 

How are Top of Rail Friction Control Materials applied?

Most early use of Top of Rail Friction Control Materials was through trackside systems, such as wayside puddle type dispensers. These continue to be popular in many parts of the world with several types of trackside application technology now used. Over the last decade or so, trainborne application systems have become more popular. These are now in widespread use, especially in European commuter rail, metro, and tram networks.

 

When should I use a Top of Rail Friction Control Material?

It is worth considering a Top of Rail Friction Control Material if you are experiencing any of the issues listed above, such as rail damage, corrugation, excessive noise, or high fuel costs. However, it is also worth noting that many operators are increasingly employing Top of Rail Friction Management on tracks without ‘issues’ as a preventative measure.

 

How can I find out more about Top of Rail Friction Management?

If you would like to know more about Top of Rail Friction Management, get in touch with us at RS Clare. You can also check out our Top of Rail Friction Control Material product page.

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