The Guillotine

In eighteenth-century France, even your execution depended on your class: nobles got the sword, commoners the rope. And a sword is only as good as the arm swinging it. In 1766 the Comte de Lally needed several blows. S01

• 1789: Dr Joseph-Ignace Guillotin proposes one method for everyone, carried out "by means of a simple mechanism". He didn't design it and he didn't build it, but his name stuck. S11 S17
• 7 March 1792: the surgeon Antoine Louis writes the real design brief. The result must never depend on a person whose "strength and skill can vary"; it has to rely on "invariable mechanical means". That's an engineering requirement, and it explains almost everything in the machine. S01
• The idea was old. By the 1500s Halifax in England had a beheading machine: a heavy block with an axe head, sliding down grooves between two posts, released by pulling a pin. Edinburgh built its own, the Maiden, in 1564. Louis's report points to the English practice. S01 S13 S14
• April 1792: the job goes to a German harpsichord maker, Tobias Schmidt, who quotes 824 livres against the official carpenter's 5,660, a seventh of the price. He tests it on straw bales, then sheep, then at the Bicêtre hospital on 17 April. Eight days later it is used for real. S04 S06 S07 S25

The three people behind it

Proposed it

Joseph-Ignace Guillotin

Doctor and deputy. Asked for one method for all classes.

Specified it

Antoine Louis

Surgeon. Wrote the requirement and the dimensions. It was briefly called the Louisette.

AI-generated

Built it

Tobias Schmidt

Harpsichord maker. No portrait of him is known, so this one is painted.

Louis's letter to the carpenter survives, so we can build it from his own numbers. A machine of roughly that age survives too, in a museum in Venlo, in the Netherlands. S03 S27

Uprights

Two oak posts, 16 cm thick (6 pouces) and exactly 32.5 cm apart (1 pied), braced at the sides and back to keep them dead vertical. S03

Grooves

A square groove 2.7 cm deep (1 pouce) down the inside of each post. Remember it: it's the most important feature on the machine, and it causes trouble later. S03

Height

Louis's draft said 3.25 m (10 pieds). The machine as built stood 4.55 m (14 pieds), "for the efficacy of the fall". S03 S05

Weight

The mouton, French for "sheep" and the name of a pile driver's ram: an oak block weighted with metal, riding the grooves on two small lugs, with a steel bar underneath to take the impact. With its blade, about 40 kg. S01 S27

Blade

A trapezoid of tempered steel, 30 cm wide, its edge at 45°, held on with three bolts. S07

Hoist

A rope from a ring on top of the weight, over a pulley at the top of each post, and down the outside. S03

Release

A rocker arm through one post hooks under the weight; a rod links it to a handle lower down the same post. S27 S28

Restraint

The lunette ("little moon"): two boards with half-circles cut out, the upper one sliding down to close. Behind it, the bascule, a tilting plank with straps. S02 S08

And the whole thing is a kit. The joints are mortise and tenon, locked with removable pins, so it can be knocked down, loaded onto a wagon and rebuilt somewhere else. The carpenter's first quote even included horses and wagons to set it up and take it down for every execution. S04 S27

Gravity does the cutting. The engineering is in holding forty kilograms four metres up, putting the target in exactly the same place every time, and letting go cleanly.

1. The bascule tips forward and slides, bringing the neck into exactly the same spot every time. S08
2. The upper lunette drops and locks it in place.
3. The executioner lifts the release handle, the rocker arm lets go, and gravity takes over. S06 S28
4. The blade falls about 2.5 m in roughly 0.7 s. By the time it reaches the neck it's doing about 7 m/s, or 25 km/h, carrying around a kilojoule. The cut itself takes a couple of hundredths of a second.
5. The weight hits the end of its grooves and the cycle runs in reverse. An assistant hauls on the rope, and because it runs through a ring on the weight, each end carries only half the load. Up it goes until the rocker arm clicks back into place. S03

E = m·g·h ≈ 40 kg × 9.81 m/s² × 2.51 m ≈ 0.99 kJ
v = √(2gh) ≈ 7.0 m/s (25 km/h)
t = √(2h/g) ≈ 0.72 s

To picture a kilojoule: a 25 kg bag of cement dropped from four metres, all of it focused onto one sharp edge.

In the 1860s an observer timed the whole process, from the first step to the basket lid closing, at fourteen seconds. S08

No machine works perfectly the first time, and this one had problems fast. In June 1792 an architect, Giraud, inspected the first machine, called it "made in haste", and wrote a snag list that reads like an engineer's. S07

• Line the wooden grooves with copper.
• Swap the wooden fittings for iron.
• Bolt the rope hooks, which were only nailed on.
• Keep two spare blades ready.

That groove

Built to Louis's numbers, the lugs have only a few millimetres of play, and damp oak swells: just 1% on a 16 cm post is 1.6 mm (our model's estimate). In July 1792 the grooves swelled and the blade failed to cut all the way through. Metal doesn't swell, so metal-lined grooves became mandatory. S07 S28

The rope and the stop

On the earliest machines the rope stayed tied to the weight and fell with it. When it snagged, executions went badly wrong. And the energy left over hit the bottom of the grooves with something like twenty tonnes of force for an instant (about 200 kN if it stops within 5 mm; an illustration, not a measurement). Again and again it knocked the frame out of line. By the 1860s the weight landed on springs topped with rubber. S08 S27

Around 1870 France rolled every fix into one national design, the Berger model, and that's the guillotine it used until 1977. S09 S10

It did its job with terrible efficiency. On 31 October 1793 the Paris executioner and his team executed twenty-one deputies in thirty-six minutes. S15

During the Reign of Terror, 16,594 official death sentences were carried out across France in just over a year, most of them by guillotine. It took a king, a queen, the chemist Lavoisier and, in the end, the revolutionaries who had used it, Robespierre included. S11 S12 S15

About eight in ten of those people weren't nobles at all. They were craftsmen, farmers, ordinary people.Of those condemned, 31% were artisans and 28% peasants S29

A machine designed to make death equal also made it fast, cheap and easy to repeat. France kept using it until 1977, and abolished the death penalty four years later. S11

Every machine on this channel gets four scores out of ten: how new the engineering was for its time, how well it did its job, how much it changed its world, and how much of its engineering lives on.

It's the first entry on the board, so for now it's in first place, and last place. Which machine should challenge it next? Tell us in the video's comments.

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