Steam Engines A series of lessons by David C Dec 2010
Part 8 Iron
Consider life in Europe in the late 1600s. Everything is built by hand, and most things are built from timber. Timber is everywhere and is easy to cut. Timber grows back.
Consequently bridges and houses, ships and carriages; all these things are made from wood. What little iron and brass appears in these things takes the form of nails, screws and other connectors.
Timber is also a good fuel. Timber fuels the fires that heat the castles and cottages, but increasingly it is being burned in furnaces to smelt metals such as lead, tin, silver, copper and iron.
For every kilogram of pure iron extracted from a furnace, 20 kilograms of wood has been consumed. No surprise then, that timber is growing hard to find in the late 1600s. It’s being chopped up faster than it can grow back.
The situation is so bad in some parts of Europe that local governments have actually banned the burning of wood.
Even in places where it’s still legal, wood is becoming hard to find and therefore becoming expensive. …all of which leaves you to wonder what an iron foundry is supposed to do to stay in business.
Well, the best alternative fuel is a shiny, black rock called coal.
Coal, you may know, is the compressed remains of forests buried by landslides millions of years ago. It burns extremely well, but it has to be dug out of the ground and cleaned and shunted from place to place in coal-wagons.
Nevertheless it’s such a good fuel that coalmining is as profitable a business as copper-mining or tin-mining.
There is a problem with coal, however, as the glassblowers in Holland had discovered: it produces a thick, black smoke that stains whatever it comes into contact with. Glass coming out of a coal-fired furnace was the colour of coal, whether you wanted it to be that colour or not.
It was also a problem for the beer-makers of Germany. To brew beer you need a fire, and if you brew beer over a coal fire, your beer tastes like coal. (Bleuch)
The Germans experimented, however, and came up with a clean kind of coal that they called “coal cake”.
If you bake coal in an airtight oven for a long period of time, you can boil off the sulphur and phosphor and other rubbish that makes coal smoke dirty, and what’s left behind is a grey rock that is almost pure hydrocarbon.
If you bake coal in an airtight oven for a long period of time, you can boil off the sulphur and phosphor and other rubbish that makes coal smoke dirty, and what’s left behind is a grey rock that is almost pure hydrocarbon. If you burn this “coal cake”, you get a very hot fire that has no fumes whatsoever.
The Dutch saw this and before long were using “coal cake” in their glass foundries. Pretty soon, the glassware coming out of their foundries was as colourless as the glassware we use today.
Now why am I telling you about glassware in Holland and beer-brewing in Germany?
Now why am I telling you about glassware in Holland and beer-brewing in Germany? Well it turns out that the ironsmiths of England were facing very much the same problem as these fellows in Europe.
Now why am I telling you about glassware in Holland and beer-brewing in Germany? Well it turns out that the ironsmiths of England were facing very much the same problem as these fellows in Europe. Iron cooked over a coal fire absorbs the muck from the fumes and this makes it brittle and useless. But iron cooked over “coal cake” comes out clean and strong.
This inspired a fellow named Abraham Darby to visit the glassmakers in Holland in 1709 or so and observe their procedures up close.
MrDarby had made a name for himself as a manufacturer of brass objects but figured that there was considerable money to be made in the iron industry if he could smelt it in a smoke-free environment.
Well, the trip to Holland confirmed his expectations. But it also gave him chance to observe something else that the Dutch glassmakers were doing, something that could be of extraordinary use to him in England.
You see, Mr Darby made pistons and cylinders and boilers for a certain MrNewcomenwho was in the business of making steam engines. MrNewcomen was unhappy about the quality of the products being delivered to him, which doesn’t mean to say that Darby’s engineers were doing a bad job but rather that MrNewcomen’s steam engines needed unusually high precision.
Cylinders and pistons had to be perfectly round and perfectly smooth and perfectly sized so that the piston could move up and down inside the cylinder without jamming, scratching or letting any air slip by.
If there were bolts or rivets to hold the parts together, then these joints had to be airtight under pressure at high temperature, which means they also had to be of perfect size and shape.
Here was the solution, right before Darby’s eyes: The Dutch glassmakers had learned to create molds into which you poured molten glass. The molds were made by pressing a desired shape into a boxful of sand and hardening the sand before you disturbed it.
As long as the thing which made the initial imprint was perfect in shape – and you could afford to take your time over this – then everything which came out of the mold would also be perfect in shape.
Furthermore, if you made several molds off the same original object, you could make several perfect copies at the same time. The Dutch had created mass production of guaranteed high-quality objects.
Darby took the idea with him back to England. In fact he even took some of the glassmakers with him to help him make sand molds for brass and iron objects. Very soon, Darby had a complete monopoly over the brass and iron industry in the UK, because the products he made were not only perfectly shaped, they were cheaper.
Now this enabled steam pumps and other machines to be built to perfection. The increasing use of iron meant that cylinders and pistons could be bigger and therefore more powerful, and the guaranteed seals meant that the engine operated for longer without requiring maintenance.
By 1733, there would be over 100 steam pumps in operation, some of them working in industries that Newcomen hadn’t even thought of when he started out in 1712.
For example, steam pumps were being used to drain swamps so that they could be turned into farms or residential areas. Steam pumps were delivering water to towns and pouring water over wheels that operated machinery in factories. Steam pumps were even pumping air through bellows into furnaces so that iron could be smelted in parts of the country that didn’t have rivers to power water wheels.
It may look as though I’m coming to the end of the story, but there’s more to be said about the process of sand-casting metal: Sand-casting enables the production of metal objects that are thinner and more delicate than can be made by hand. This included measuring devices and tools for making other tools.
By 1750, metal lathes had replaced wooden lathes, and by 1760these metal lathes were controlled precisely by wheels and gears so that machinery could be carved out of raw metal to a precision never seen before. This machinery was very often going to be the wheels and gears needed to make more accurate machine tools. The circle had closed on itself; technology was making more technology.