How locomotives pull fifty times their own weight

Technology · Published 30 October 2026 Swipe more like this →

In short: Moving ten thousand tons of freight requires more than just raw power; it is a masterclass in physics. This video explains the four engineering principles that allow heavy trains to glide across the land.

Locomotives overcome immense resistance through four key mechanisms. Initially, rolling friction becomes minimal because steel wheels on rails have a contact zone near a dime's size per wheel and a coefficient of 0.35 to 0.5. Second, locomotives use concentrated mass for traction; modern freight engines weigh between 370,000 and 430,000 pounds to ensure enough pressure at each contact point to prevent slipping.

The third factor is the efficiency of AC traction motors, which convert about 80% of engine power into pulling force. Lastly, slack action is enabled by 'draft gears', which permit pulling individual cars sequentially instead of overcoming the whole train's static friction simultaneously. Together, these refinements from over 150 years of development make moving massive weights possible.

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