invention5

Lienhard
How Invention Begins ch. 5

We start this chapter still in the world of the scientists--they are looking to understand principles. What are the rewards for making a scientific discovery?

maybe you even get a unit or something you have discovered named after you
you publish it--get credit for it
you become respected among scientists
scientists aren't usually as interested in inventing useful things or in getting rich
would you rather be as rich as Bill Gates or win the Nobel Prize?

Who gets the credit? Traditionally the scientist, not his assistants (even if they were scientists themselves)

Papin's steam digester

Denis Papin

worked with Robert Boyle and Christian Huygens
in 1690 published a design for an atmospheric engine--a steam engine that got its power by condensing the steam, like a Newcomen engine--but it wasn't built
he even proposed a high pressure steam engine (the idea that later replaced the atmospheric engine) but the technology wasn't there
people were even playing with designs for steam turbines

Many scientists and inventors were members of religious minorities because most professions were closed to them

in England you had to belong to the Church of England in order to be a lawyer or hold a government job, other kinds of protestants, called dissenters, were not allowed to hold such positions or even to go to the best universities
France was Catholic--for a while it tolerated a protestant minority called the Huguenots, but then they were told they would have to convert or leave the country because the king feared they were disloyal
in England the dissenters also became the leaders of the industrial revolution--after 1700 the new science begins to lead to new technology as well

Now we will move from science to technology

An industrial revolution is a fundamental economic change:

between 1770 and 1850 the economy of England changed from mostly agricultural to mostly industrial
why England? for one thing economy more capitalist, maybe because of the religious pattern in England
this was the result not of one key invention but of technological progress in different fields coming together
its center is the development of factories (which hadn't really existed before this time), but they couldn't have developed without better transportation creating larger markets and better transportation couldn't have existed without the growth of the iron industry, which couldn't have grown without steam engines
society had a hard time adjusting to the new economic system

Iron:

by 1720 most iron in England was imported due to a shortage of charcoal for smelting
in 1709 Abraham Darby invented a way of smelting iron using coke (processed coal) instead of charcoal
the iron industry took off after 1760 since iron ore and coal were both very plentiful in England
the only snag was that water had to be pumped out of the mines (a mine acts like a well and fills with water)
1779 Iron Bridge ( photo )

the first iron bridge, Coalbrookedale

The early practical steam engines are all atmospheric engines

To understand, do this experiment:
Take a plastic container, put a little water in it, and put it in the microwave until the water boils
take it carefully out of the microwave (without burning yourself) and put a lid on it tightly while it is still steaming hot
let it cool and you will see that the lid is pulled down (curves downward into the container)
When you put the lid on the container was full of steam
when it cooled the steam condensed and turned back into water
the water takes up much less space than the steam, so the lid is pulled down
an atmospheric steam engine works on the same principle--fill the cylinder with steam and then condense it
have a piston that moves in the cylinder--when the steam condenses the piston is pulled down
attach the piston to a water pump so that each time it is pulled down it pulls up the handle of the water pump and pumps water

Early Steam Engines:

The need for steam engines was to pump water out of mines
Thomas Savery built the first workable engine, using an odd design without a cylinder and piston--using the steam directly to pull up the water (animation)
Newcomen Engine (about 1712) filled a cylinder with steam and then sprayed in cold water to condense the steam and draw the piston down. 1/2% efficient, but widely used to pump water out of coal mines. (animation)
some scientific knowledge about atmospheric pressure/vacuum was necessary, but it was a one part of building an engine
Watt Engine (1774) had had a separate condenser, making the engine much more efficient. The cylinder always stays hot and the steam is condensed in a separate chamber called a condenser which always stays cold. You don't waste a lot of energy heating and cooling the walls of the cylinder (animation)
James Watt later added:
- sun and planet gear converted reciprocating (up and down) motion into rotary motion to power machines
- automatic control mechanism to keep the engine running at a fairly constant speed
- double-acting engine made for much smoother power--close the cylinder above the piston and put steam into the top part of the cylinder while condensing steam in the bottom part and then vice versa
- more efficient engine using a separate condenser

Watt Engine

high pressure engines developed after 1800, needed for transportation applications (the Watt engine was too heavy)
significance of steam power

This page written and copyright Pamela E. Mack

HIST 122
last updated 8/31/07