Linear motor

In 1841, Charles Wheatstone received a patent for a device that seemed obvious: take a rotary electric motor, cut it open, and roll it flat. By 1845 at King's College London, he built the first linear motor where electromagnets pulsed in sequence to drag an aluminum component along a line. The concept was elegant. The execution was premature—anemic 1840s batteries couldn't generate enough power. The linear motor would wait for its adjacent possible.

In 1905, German engineer Alfred Zehden filed a patent describing feasible linear induction motor for trains. By then, AC power systems had spread and electromagnetic theory was mature. In 1935, Hermann Kemper built a working magnetic levitation model. But the modern linear motor didn't arrive until the late 1940s, when Eric Laithwaite at Manchester University developed the first full-size prototype.

Linear motors are rotary motors "unrolled"—eliminating mechanical conversion systems like gearboxes, ball screws, and belts. A rotary motor spins a shaft; creating linear motion requires friction-prone intermediaries. A linear motor's primary (stator) creates electromagnetic fields pushing a slider directly along a track. Performance difference is stark: linear motors reach 400 inches per second with 10g acceleration versus rotary's 20-40 inches at 2g. Accuracy improves 500x over rotary steppers. Efficiency jumps from 55% to over 90%.

The biggest impact came in maglev trains. The Japanese L0 Series reached 603 km/h in 2015. Shanghai's maglev held commercial speed record at 431 km/h. Superconducting magnets generate fields ten times stronger than ordinary electromagnets—enough to suspend trains without wheels or friction.

Beyond maglev: CNC machining, roller coasters launching trains to 128 mph in 3.5 seconds, ropeless elevators traveling vertically and horizontally, and the Navy's Electromagnetic Aircraft Launch System flinging jets to takeoff speed in two seconds. The invention Wheatstone sketched when batteries were too weak now powers the fastest, most precise machines on Earth.