Newcomen Engine

One of the problems when doing any sort of mining work is that water will inevitably accumulate in the lower regions, making it impossible to dig further down or to continue work in the lowest level. Draining the mine by hand is an extremely difficult and time consuming task, adding much labor to the already arduous task of mining the rock. During Newcomen's time, horses were used to help drain tin mines, but this was a very expensive solution. What was needed was something that was tireless and cheap to maintain.

Newcomen devised a machine that would sit atop the mine and slowly draw water up from the depths, utilizing the powerful pressure found in steam to make it run. From a distance, the Newcomen engine looks much like modern day oil pumps. A large wooden crossbeam is supported from its middle, forming a large T. One side is a pipe that goes down into the bottom of the mine and will draw out water. The other end is connected to a large piston which is in turn connected to a supply of steam.

In order to understand how it works, visualize the engine with the piston side down and the pump side raised in the air, like this \. A valve is opened and steam begins to fill the large cylinder, slowly pushing the piston upwards. When produced in large quantities and confined to small volumes, steam produces a large amount of pressure, and it is this force that pushes the heavy piston. As it rises, the pipe on the other end of the beam plunges down into a well that leads to the bottom of the mine. The engine now looks like this /. Now we're ready to bring the water back up. Water is sprayed into the cylinder, causing the steam to immediately condense back into water form. This reduces its volume immensely (steam has many more times the volume of water) which creates a vacuum. Atmospheric pressure then pushes on the piston, tilting the beam back to its original position, drawing water out of the ground.

Several variations on the Newcomen engine were developed, though the only significant alteration was made to it in 1768 by James Watt. The problem with the engine was that it was horribly inefficient. When water was sprayed to condense the water, the cylinder was also cooled. As the steam once again filled the chamber, it would come in contact with the cool sides and condense, losing its heat energy to the metal. Only when the metal had heated up to 100 degrees Celsius could enough pressure build to push the piston. It has been calculated that only 1% of the energy spent was ever used to drive the piston; the other 99% was lost heating the cylinder. Watt realized that this problem could be avoided by the insertion of a second cylinder, the condenser, allowing the main cylinder to maintain a more constant temperature. This allowed the engine to run at a much higher level of efficiency.