The discussion revolves around modifying a 1930s Lionel O gauge train to implement a speed limiter, as the current setup leads to difficulty in maintaining a consistent speed without stalling. The user has experimented with various controllers, including SCR/TRIAC and PWM setups, but has found limited success in controlling the train's speed effectively. A proposed solution involves using an optical detector to monitor wheel revolutions, paired with a circuit using 555 timers to cut power when the train exceeds a set speed threshold. The user aims to create a reversible modification that allows for easy restoration of the train to its original state. Overall, the goal is to enhance the train's usability for future family gatherings while maintaining its sentimental value.