Hot, Wet, and Steamy

Hot, Wet and Steamy     by Mike Creasy

 

The idea of using steam to move things has been around for a long time, and seems to be making a comeback at Harrison Model Yacht Pond, so this might be a good time to look back at the development of steam as a mode of power. ​​ 

 An English military engineer by the name of Thomas Savery got a patent on a very crude steam engine in 1698. ​​ He was looking for a better way to pump water out of mines, which was being done by teams of horses pulling large buckets up a shaft to the surface. ​​ Savery's device used a sort of venturi system to blow steam and water up a pipe - not very effective, but it did start the wheels turning in a number of inventive minds.

 By 1712, Thomas Newcomen had built a pumping engine which used steam to move a piston which, in turn, moved a water pump. ​​ Newcomen's engine used a fulcrum or beam to connect the engine to the pump, which meant that the engine could be at the surface and the actual pump could be down in the mine. ​​ This was a major step forward, since having a fire burning in the methane-rich air of a coal mine was not a good way to grow old!

 In 1775, James Watt had come up with a number of improvements including a steam condenser and a compound cylinder. ​​ Watt's later engines had a throttle valve and a centrifugal governor to control speed. ​​ Interestingly, the manufacturing processes of the day were simply not up to the task of producing sound boilers. ​​ Explosions were common, and Watt restricted his engines to very low pressures. ​​ Still, Watt engines were effective enough to be used to power textile mills and things, leading to the start of the "Industrial Revolution". ​​ (Those of you who don't much care for the Wal-Marts of this world can start booing now!)

 In 1813, a fellow named George Stephenson was working in a coal mine in Newcastle. ​​ Like most such mines, this one used teams of horses to drag coal carts along wooden tracks. ​​ Stephenson saw how steam could be used to pump water, and began to consider how steam could move coal. ​​ In July of 1814, his hand-made locomotive "Blucher" moved 8 loaded coal wagons up an incline - starting a revolution in the transportation business.

 Steam continued to evolve as a source of power, but the development of high-pressure steam was still limited by the manufacturing techniques of the day. ​​ Uneven metal quality, poor riveting, slow production of tubing and even the development of the metal lathe all meant that early steam power was both low pressure (under 60 psi) and high risk! ​​ This wasn't a big problem on land, or even on the rivers where fresh water and fuel were readily available at trackside or on the riverbank.

 No surprise then, that all early steamships were meant for inshore or river use. ​​ Side- and stern-wheel steamers dominated the early days of steam from 1805 to about 1850.  ​​​​ These inefficient drivers, coupled with and inefficient engine, meant that range stayed short... not very useful out on the bounding main.

 Steam has an interesting quality when used in an engine - as it expands, it cools very rapidly. ​​ This cooling is most pronounced when the exhaust pressure is close to atmospheric, as it was in these early, single cylinder engines. ​​ The thermal shock -between hot, pressurized steam and cool exhaust steam - lead to lots of problems with cylinder walls and piston tops. ​​ One solution was to exhaust the steam at higher pressure, but this meant the engine became even more inefficient, and so the idea of a compound engine - with steam used more than once - was born.

 Train engines were the first to apply this idea beginning around 1805. ​​ It wasn't until some time between 1824 and 1850 that compound engines first showed up on the water (depending on who you believe!). ​​ Triple and quadruple expansion engines soon solved the efficiency problem. ​​ Combined with increasing (safe) boiler pressures and other gadgets, such as condensers (to save water) and injectors (to keep the boiler full) these increasingly refined steam plants soon became the standard for oceanic, as well as inshore, ship power.

 Its easy to understand how steam engineers become so passionate about their babies; a big steam engine makes almost no noise when running. ​​ They seldom turn more than a few hundred rpm and they'll go for a long time with the right care and attention. ​​ They'll even keep you warm!

 So all you sail types: next time you're out in a frigid wind with a rope and some frozen bedding, think of the romance of steam where you could be hot, wet and steamy!  ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​​​  

 

Bibliography

 

Saltscapes Magazine, Full Steam Ahead by Doug Scott, May/June 2007

Conway's The Advent of Steam, Dr. Basil Greenhill, Chartwell Books, 1993

wikipedia.com

inventors.about.com

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