Borrowing from rail

With reference to your article 'Shock Treatment' (News, 18 June) the idea of a car that combines the best of an electric traction system with an internal combustion engine is a very old and well-established concept.

Not for a car, though, but trains. In fact, many of the ideas now being credited to the automotive industry have been used in our rail locomotives and trains for decades. For example, the idea of Direct Injection for diesel engines is well over 50 years old, the concept and application of regenerative braking is extensively used on electric trains, and the method of having an internal combustion engine driving a generator to operate independently-powered axles through electric motors originated in the UK in the 1950s.

In fact, the railways are moving away from optimised internal combustion engines powering electrical generators that in turn drive electronically-controlled motors to all-electric trains with even better performance.

Existing UK diesel trains, such as the IC125, use their engines to power an electrical generator. This means the engine is running at its optimum efficiency. The output from the electrical generator is then delivered in a controlled manner to electric motors powering eight axles for one train.

Using this method, the engine is running under the best conditions for maximum efficiency, and electric motors provide a near-ideal tractive effort; in other words, maximum torque when starting, and increasing back EMF when running thereby reducing the power demand.

Perhaps the automotive industry needs to consider 50-year-old rail technology as a means to move forward, or perhaps even use the other very old railway locomotive transmission method, diesel hydraulic, with further benefits in terms of even better tractive effort.

Andrew Porter

Cambridge