Review of “Engineering the Revolution” by Ken Alder

Interchangeable Parts: Not Just an American Story

Technically, it is about interchangeable parts manufacturing. While David Hounshell’s “From the American System to Mass Production, 1800-1932” told the story of this technology in the US, alluding only briefly to the earlier work done in France, Ken Alder makes this early work the focus of his book. He opens with what may have been the most consequential meeting in the history of manufacturing, when American ambassador Thomas Jefferson visited Honoré Blanc’s lab at the Château de Vincennes on July 8, 1785 and witnessed a demonstration of musket lock assembly from bins of parts. Alder then flashes back in time to the developments that led to this passing of the baton.

Growing up in France, I had been taught that it had missed the boat on the industrial revolution. I have polled French engineers about the key figures in Alder’s book, Pierre Vaquette de Gribeauval and Honoré Blanc. A few, who work in the defense industry, had heard of Gribeauval as the designer of both the French weapon system used in the Revolution/Napoleonic era and of the strategies and tactics to put it to use. But they did not associate his name with interchangeable parts.

No member of that group had ever heard of Honoré Blanc. I could not find a picture of Blanc anywhere, but I did find pictures of his handiwork, like a gunlock with interchangeable parts made for the M1777 musket. His only known publication is an Important memorandum on the manufacture of weapons of war addressed to the National Assembly in 1790. The French revolution had cut off the support he had enjoyed in the royal regime, and he wrote this memo as a plea to the new authorities.

He speaks of himself in the 3-rd person, as ‘Mr. Blanc’, and not only explains what he did but he also describes, perhaps too candidly for his purpose, the difficulties he encountered to get his methods accepted in armories.To give concrete examples, he enters into details that parliamentarians, then or today, certainly would not follow, such as the disastrous consequences of not having standards for taps and screws. It shows the struggles of an inventor whose ideas were widely applied 100 years later.

Even though Jefferson did not believe in developing manufacturing in the US, as president, he initiated a 50+ year development effort that eventually succeeded, was essential to the growth of manufacturing, and created the machine-tool industry. The broad outlines of the American part of the story are taught to American school children and associated with the name of Eli Whitney, but nobody in France seems aware that there ever even was such a thing as “interchangeable parts technology.” It is American historians of technology, like David Hounshell and Ken Alder, who are lifting the French precursors from obscurity.

Hounshell’s book had left me with the perception that the reason the development of interchangeable parts had failed in France was that metal working technology was not ready, particularly the machining of steel after heat treatment. Alder points instead to social resistance against a disruptive technology. According to Alder, it failed, not because it couldn’t technically be made to work, but because the established arms industry blocked its implementation.

The subtitle of the book indicates 1763 to 1815 as the time span of his investigation, from the end of the Seven Years’ War, during which the poor performance of French weapons motivated the start of this effort, to the fall of Napoleon, who ended it. Alder, however, goes further in time in both directions, providing for the earlier decades insights about the origins of the modern engineering profession and of the peculiarities of the French engineering education system. For the decades after 1815, he describes how the technology eventually returned to France after a hiatus of 50 years, as “the American system of manufacture.”

Birth of the engineering profession

When, as Ken Alder does , you pull on the “Gribeauval” thread, you find a wealth of unexpected information on topics other than business and production methods, including the origin of the engineering profession as we know it.

The term “engineer” originally designated people working for the military, in the design of fortifications or weapons. Until the 18th century, they had relied exclusively on know-how passed on by generations of craftsmen. Early in the 18th century, the French artillery service created schools to train officers who could advance the technology by merging the modern science of the day — Newtonian physics — with the craftsmen’s empirical know-how.

The graduates were the prototypes of what we now know as engineers. Gribeauval was a product of this system, as was Napoleon Bonaparte. The self-taught Blanc, on the other hand, had begun his career as an apprentice gunsmith at the age of 12, and his background is similar to that of many manufacturing innovators to come, from Frederick Taylor to Taiichi Ohno.

I was always been struck that the word “ingénieur” for this profession is essentially the same in German, Russian, Italian, and Spanish, while it is different in English. An “ingénieur” is ingenious; an “engineer” drives a locomotive. The connotations are different and reflect a difference in the social status of the profession in continental Europe and in the English-speaking countries. “Ingénieur” and Engineer in fact have the same remote origin in the designers and builders of fortifications and armaments.

Among other things, the goal of the artillery schools could only be reached with students willing and able to master Newtonian physics. But the army officer corps had, until then, been a preserve of the nobility, whose horseback riding sons were more likely to be effective at leading a cavalry charge than organizing to move, set up, point and fire cannons accurately. To recruit more cerebral candidates, these schools selected them on math abilities that were far beyond anything they would need in the field. 300 years on,  engineering schools still do.

Technical limitations

The plan to apply contemporary physics to artillery ran into difficulties that did not all have to do with the reluctance of craftsmen to change. Early 18th century science couldn’t quite predict the trajectories of cannonballs. At first, it was treating them as if they were flying in a vacuum, and a theory of air resistance was not worked out until Benjamin Robins in England and Leonhard Euler in Germany did it in the 1740s and 50s. The cannons of the day also tended to throw curve balls, and spinning cannon balls deviated enough to miss their targets. A theory explaining this, the Magnus effect, was another century away.

And finally, the production of cannonballs was so imprecise that you had ±20% of variations in diameter. The smaller ones would leave gaps through which the explosion gases would escape without providing the expected propulsion. With this level of variability, the best ballistics models would have made no difference. There was no hope of having a science-based method of aiming guns unless you could make them straight, with consistent dimensions, and you could load them with consistent ammunition. In other words, the whole artillery system had to be built with interchangeable parts.

Making a 100,000 consistent muskets with the manufacturing technology of the day was a challenge. The Farenheit and Celsius scales were invented about that time, but there were no thermometers to measure the temperatures used for heat treatment in forging. Instructions called to make the iron “cherry red,” which covers a range of colors.

The techniques used in the 18th century to make a rifle in 300 hours are reenacted and summarized in the following 58-minute video of gunsmith Wallace Gusler, shot at Colonial Williamsburg in 2013:

https://www.youtube.com/watch?v=lui6uNPcRPA

The first product successfully manufactured with interchangeable part, however, was not a gun but a gun carriage, about 1765. Under the leadership of Gribeauval, they were built in national armories and did not require the tight tolerances of the guns themselves. Honoré Blanc undertook it for muskets, which was a different challenge. Technically, it involved (2) making and assembling precise small parts into gun locks, and (2) forging gun barrels by hand. And the muskets were not built in armories but in small shops by contractors with at most a handful of employees, who were not keen to invest in machinery or share their proprietary know-how.

Rejection by the Arms Industry

Technically, Gribeauval and Blanc were more successful than I previously believed based on Hounshell’s account. They introduced technical drawings, based on Monge’s descriptive geometry, with critical dimensions and tolerances, go/no-go gauges, fixtures and jigs, and machines for forging, turning, milling, drilling and reaming that were powered by horses, water, or people. Gaspard Monge is actually better remembered than either Gribeauval or Blanc; he has a street, a square, and a subway station named after him.

The first product successfully manufactured with interchangeable part, however, was not a gun but a gun carriage, about 1765. Under the leadership of Gribeauval, they were built in national armories and did not require the tight tolerances of the guns themselves. Honoré Blanc took up muskets, which were a different challenge. And the muskets were not built in armories but in small shops by contractors with at most a handful of employees, who were not keen to invest in machinery, share their proprietary know-how, or congregate in factories.

In musket making, the relationship between the military procurement engineers and their contract manufacturers were almost unbelievably brutal, particularly in the Saint-Étienne area, South of Lyon which, according to Alder, did not speak French at the time but Provencal. The engineers in charge of testing and accepting muskets had the authority to jail recalcitrant suppliers, and used this authority, but there were limits to the extent you could pressure people who made the most lethal weapons of the time, and were determined to keep control over that activity.

Alder’s account is of 50 years of engineers vainly trying to force new technology onto an industry that rejected it, even though embracing it would have been in its best interest, not to mention that of the country. This struggle continued through three political regimes. It started under Louis XV, and went on right through the Revolution and the Napoleonic eras. Gribeauval cannons were made by the thousands, and used not only in Europe but also in the American Revolutionary War. Muskets were made by the hundreds of thousands, but too few with interchangeable parts to make a difference.

In the end, the French engineers lost the fight and left a clear field to their American counterparts. Towards the end of the 19th century, interchangeable parts returned to France as the American System of Manufacture.

Interchangeable parts today

French contributions to manufacturing