On this page
In 1813 most engineers believed a heavy engine could not grip a smooth rail, so its wheels would simply spin. George Stephenson thought they were wrong, and the railways that followed proved him right. This post covers what he did, the physics behind his bet, and what a student can learn from a man who taught himself to read as an adult.
Who was George Stephenson?
According to Encyclopaedia Britannica's biography, Stephenson was born on 9 June 1781 at Wylam, Northumberland, the son of a mechanic who ran a Newcomen steam engine pumping water from a coal mine. He went to work early, with no formal schooling, and by 19 was running a Newcomen engine himself. He then enrolled in night school to learn to read and write.
His skill with engines made him enginewright, or chief mechanic, at Killingworth colliery. He sent his son Robert to school in Newcastle to learn mathematics, and every evening the two went over Robert's homework together, so that both of them learned. Robert later became a famous engineer in his own right.
Why did Stephenson trust smooth wheels on smooth rails?
Britannica describes how, in 1813, Stephenson studied an engine by John Blenkinsop that drove a toothed wheel along a cogged third rail, because Blenkinsop believed plain wheels could not grip. The cogs broke down often. Stephenson built his own engine, the Blücher, with plain wheels. It pulled eight loaded wagons carrying 30 tons of coal at 4 miles per hour.
The question he was really answering is one you meet in every friction chapter: is the maximum static friction between wheel and rail bigger than the force needed to pull the train?
Worked example (sample numbers). These figures are for a classroom model, not measurements of the Blücher. Suppose the driving wheels carry 5,000 kg, the coefficient of friction between iron wheel and iron rail is 0.2, and the train has a mass of 30,000 kg with a rolling resistance of 0.01 of its weight. Take g = 9.8 m/s².
Largest forward push the wheels can get from the rail before slipping: F = μmg = 0.2 × 5,000 × 9.8 = 9,800 N.
Force needed to keep the train rolling on level track: 0.01 × 30,000 × 9.8 = 2,940 N.
Since 9,800 N is more than 2,940 N, plain wheels can pull the train without slipping.
Power at 4 mph: 4 mph = 4 × 1,609.344 ÷ 3,600 = 1.79 m/s, so P = Fv = 2,940 × 1.79 ≈ 5.3 kW.
Now put the same train on a slope rising 1 m for every 100 m. The extra force is about mg × (1/100) = 2,940 N, so the total doubles to 5,880 N. Steeper slopes eat into the grip quickly, which is why a railway needs gentle gradients. Our guide to friction in block problems covers the same reasoning step by step.
What happened on the Stockton and Darlington Railway?
In 1821 Stephenson heard of a planned line from Stockton to Darlington, and its promoter, Edward Pease, commissioned him to build a steam locomotive for it. Britannica records that on 27 September 1825 the first public passenger train on the line was pulled by Stephenson's engine Active, later renamed Locomotion. He then surveyed and built the Liverpool and Manchester Railway, about 40 miles long, against strong opposition from landowners. When it opened on 15 September 1830, all eight of its locomotives had been built at the Stephensons' works in Newcastle.
What made Rocket win at Rainhill?
Before the Liverpool and Manchester line opened, its directors held locomotive trials at Rainhill in 1829. The Science Museum Group's record for Rocket credits the design to Robert Stephenson, built by Robert Stephenson and Co. in Newcastle. Rocket was the only one of five entrants to complete the trials, averaging 12 mph with a top speed of 30 mph. The Stephensons won the £500 prize and the contract to build the railway's locomotives. The museum notes that Rocket brought together the multi-tube boiler and the blast-pipe, and that it set the pattern for later engines even though it was rebuilt within 18 months.
A National Railway Museum release from 2023 adds that Rocket was built at Robert Stephenson and Co., which it calls the world's first locomotive workshop.
Why many tubes? Heat passes from hot gas to water through the tube walls, so more wall area means faster boiling. Take one flue of radius R and replace it with n tubes of the same total cross-section, each of radius R/√n. The total wall length around them is n × 2π(R/√n) = 2πR√n. With 25 tubes, the heating surface is 5 times larger for the same gas flow area.
What can a student take from Stephenson's way of working?
Test the belief, not the authority. Experts said smooth wheels would slip. He built one and measured what it could pull.
Learn the basics late if you must. He learned to read as a working adult, then learned alongside his son.
Improve one part at a time. Rocket did not appear from nowhere; it built on years of colliery engines.
If friction diagrams are what trip you up, the Fermi Simulation Lab has interactive simulations for ideas that are easier to see than read, so you can watch how forces change before you write the equations. For the engine that came before Stephenson's, read our post on James Watt and the separate condenser.
This week, redo the worked example with a 1-in-50 slope and find the steepest gradient your sample train could climb.
