An idea older than the petrol engine — the rotating magnetic field — finally gets its battery.
2012·AC induction — an 1888 idea·310 kW (P85)·1·Single fixed ratio
1· THE STORY
The oldest idea wins in the end
The Model S drive unit is an induction motor Nikola Tesla would recognise from 1888: three windings take turns pulling, the magnetic field spins, and the rotor chases it. One moving part, full twist from a standstill, no clutch and a single fixed gear. It did not wait a century for a better motor — it waited for a battery worth carrying. When lithium cells finally held enough energy, the engine this whole timeline built became optional.
AC induction — an 1888 ideaMotor310 kW (P85)Power
2· WHY IT MATTERED
Full torque at zero rpm
A petrol engine makes nothing below idle — it needs revs, a clutch to slip, and a gearbox to keep it in its narrow happy band. A motor’s torque is there from the first degree of rotation, at maximum, silently. That is why an electric saloon embarrasses sports cars away from the lights: not exotic engineering, just physics that never needed warming up.
3· WHY IT MATTERED
One moving part
No pistons, valves, cams, belts, oil circuit or exhaust — the rotor spins, and that is the entire mechanism. The gearbox shrinks to one fixed reduction because a motor’s usable band is enormous. Nearly everything this timeline’s engines accumulated — the four strokes, the valvetrain, the boost, the balance — is simply deleted.
Tesla’s motor predates Otto’s engine reaching cars; what was missing for 120 years was energy worth carrying. Petrol holds vastly more energy per kilogram than any battery — engines could afford their inefficiency. Only when lithium cells crossed the line of a usable range did the maths flip, and the motor collected a century of interest at once.
5· TRY IT
Chase the field
Three coils take turns pulling and the magnetic field spins — scrub it slowly to catch the trick, then check the torque curve that made every engine before it feel old.
Readout
Field speed at 50 Hz3,000 rpm
Rotor (4% slip)2,880 rpm
Torque at 0 rpm100%
Moving parts1
The inverter conducts: raise the frequency and the field — and the car — simply goes faster, no gears involved. Tesla patented this machine in 1888; the battery that made it a car engine took until now. The timeline ends where electricity began.
Deep dive · No clutch, one gear· opened from Tesla Model S drive unit
Timelines · Engines · go deeper · Tesla Model S drive unit
No clutch, one gear
A petrol car needs six gears to fake what a motor’s torque curve simply is.
1 — fixed·none·100%·recharges the battery
1· THE IDEA
Tractive effort: six overlapping gear curves against one smooth motor line
A gearbox exists because a petrol engine is only strong in a narrow band of revs — below it it stalls, above it it screams, so the transmission endlessly re-matches engine speed to road speed. An electric motor’s torque is at maximum from zero rpm and its usable band spans the whole road-speed range, so the entire apparatus — clutch, gears, shifts, the tachometer itself — reduces to one fixed reduction gear. Fewer parts, nothing to interrupt the push, and a throttle pedal that works in both directions.
2· WHY IT MATTERS
The sawtooth versus the curve
Plot the pull at the wheels against road speed and a petrol car draws a sawtooth: each gear’s curve rises, peaks and dies, and the gearbox jumps to the next one, losing the top of every curve to the shift. The motor draws one unbroken line over the whole range — the ideal the sawtooth was always trying to approximate.
3· WHY IT MATTERS
The pedal that refuels
Because a motor and a generator are the same machine run in opposite directions, lifting the accelerator turns the drivetrain into a brake that charges the battery. One-pedal driving is not a gimmick — it is the machine’s symmetry showing through, and it is where a town car recovers a large share of its energy.
4· WHY IT MATTERS
What disappears from the bill
No clutch to wear, no gearbox oil, no torque converter, no rev-matching, no service items in the driveline worth the name. The EV’s mechanical simplicity is not a marketing line: it is most of a century of transmission engineering being made unnecessary by a better torque curve.
5· TRY IT
Drive the sawtooth
Slide the road speed and watch the petrol car hop between gear curves while the motor rides one line — the picture that explains why the EV’s gearbox is a single reduction.
Readout
Best petrol gear gives61%
The motor gives92%
Shifts neededpetrol: 5 · motor: 0
Normalised shapes, honest physics: each gear re-scales the same narrow engine band, while the motor holds full torque to its base speed and constant power beyond. This chart IS the reason an EV needs neither clutch nor gearbox.