Dave steam 12 (what goes round)(36)


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Dave steam 12 (what goes round)(36)

  1. 1. Steam Engines<br />A series of lessons <br />by David C<br />Dec 2010<br />
  2. 2. Part 12<br />Murdock<br />
  3. 3. Okay now I want to pick up the story from about ten years after James Watt introduced the third generation steam pump, the first two being those of Thomas Savery and Thomas Newcomen. <br />
  4. 4. Watt’s pump uses about a fifth as much fuel as its predecessors and therefore is drawing a lot of attention from people who previously could not afford the fuel costs of a steam pump. <br />He’s also getting letters from people in industries that he can’t help; people that want machines that can turn wheels for example. <br />
  5. 5. Now the steam pump in the 1770s, despite being a wonderful new invention, can’t turn wheels. <br />This is the one thing that keeps steam pumps in second place behind water wheels, in terms of how useful they are in industry. <br />
  6. 6. A water wheel turns an axle that reaches into a factory and operates a conveyor belt or a grindstone. <br />A steam pump can only go up and down, and though attempts had been made to turn this up-down motion into rotary motion, none of these had ever been satisfactory. <br />
  7. 7. In principle, you’d think it would be easy. <br />All you’d need to do is attach a crank handle <br />to the end of the piston and have that turn a wheel. <br />
  8. 8. But here’s the problem. The steam pump is driven <br />by a series of explosions. The piston shoots in one direction and slowly returns to its starting point. <br />The up-and-down motion is too jerky to turn a wheel, and won’t be until there is some way to smooth out its action. <br />
  9. 9. Enter the double-action piston, invented by James Watt in 1781, <br />or maybe by one of his employees. <br />It’s getting hard to tell now, because Watt’s company is now <br />quite huge and there are dozens of people working for him. <br />All of the inventions coming out of this factory are patented to James Watt, whether he has a direct hand in the invention or not, <br />so we don’t know for sure that the double-action piston <br />really is his work. <br />
  10. 10. Anyway, the double-action piston is a very clever <br />and – in hindsight only – a very obvious way <br />of getting more energy out of a piston. <br />Here you are using a burst of steam to push the piston up<br /> and another burst of steam to push the piston down. <br />
  11. 11. As steam is entering on one side, a vacuum is sucking steam <br />out the other side so that there is double the force driving the piston <br />and therefore double the power on any stroke. <br />
  12. 12. Very likely, Mr Watt was thinking only in terms of making the steam pump ever more efficient than before, as he had done several times before <br />and would continue to do for the rest of his life. <br />
  13. 13. But the unexpected benefit of the double-action piston <br />was that the up-stroke was now as quick and forceful as the down-stroke, and that meant it could be used to drive a crank <br />to turn a wheel. <br />
  14. 14. But the unexpected benefit of the double-action piston <br />was that the up-stroke was now as quick and forceful as the down-stroke, and that meant it could be used to drive a crank <br />to turn a wheel. <br />Well, with a few modifications here and there. <br />The most useful thing to add now is a flywheel. <br />
  15. 15. This is a wheel of very large diameter that has <br />most of its weight out there on the perimeter. <br />It’s very sluggish and doesn’t want to move. <br />
  16. 16. But when it finally has been coerced into movement, <br />it wants to keep moving at that same speed <br />no matter what happens to be tugging at it or pushing on it. <br />
  17. 17. This is an effect called inertia; it smoothes out <br />the remaining jerkiness in the piston action <br />so that the axle will turn smoothly. <br />
  18. 18. The story would be very simple at this point if Mr Watt <br />had simply attached a crank handle and flywheel to his <br />double-action piston and used it to turn an axle. <br />But here the business of patents raises its ugly head again <br />and causes trouble. <br />
  19. 19. One of Watt’s competitors had already applied a crank handle and flywheel to a steam pump that he was designing, <br />and had managed to patent the idea under his own name<br />
  20. 20. One of Watt’s competitors had already applied a crank handle and flywheel to a steam pump that he was designing, <br />and had managed to patent the idea under his own name<br />…which meant that Mr Watt was not allowed to use a crank and flywheel on any of his steam pumps. <br />
  21. 21. This inspired Mr Watt to come up with something <br />that did exactly the same job as a crank and flywheel <br />but was actually something else. <br />
  22. 22. Here’s what one of his engineers came up with. <br />It does exactly the same job as a crank and flywheel but looks different enough to be called something else. <br />This is called the ‘sun-and-plant gear’.As the wheel on the piston rod orbits around the axle, it turns the wheel.<br />
  23. 23. It was different enough in appearance for Mr Watt to apply <br />for a patent on it, separate from the patent on the original <br />crank-and-flywheel; and being a big and influential company <br />with powerful connections everywhere, they managed to get it. <br />
  24. 24. It strikes me as being more than a little unfair that they did, <br />but the impact on history can’t be denied: <br />Putting some kind of crank and flywheel arrangement together<br />with the double-acting piston meant that Mr Watt’s steam pump<br />could now turn a wheel smoothly, and thoroughly replace <br />the water wheel as the driving force of industry. <br />
  25. 25. Now, there was no limit to what the steam pump could do, <br />and it is a fair time for me to stop calling it a pump<br />and start calling it an engine. <br />
  26. 26. The number of industries interested in the steam engine multiplied <br />very quickly. Even people as far away as the newly established <br />‘United States of America’ were interested in buying steam engines <br />from Boulton,Watt and company.<br />
  27. 27. There were even a few fanatics who thought a steam engine <br />might be able to operate a paddleboat, now that a powerful <br />steam engine was small enough to fit onto the deck of such a thing. <br />
  28. 28. Let me now introduce you to MrWilliam Murdock, a fabulous young fellow who worked for Boulton, Watt and company and was quite possibly the greatest inventor of his generation. <br />
  29. 29. He was the fellow who came up with the sun-and-planet-gear, not to mention all the other clever things he invented or modified while working on steam pumps.<br />
  30. 30. William Murdock was the sort of fellow that would spend his working day coming up with clever inventions that would make steam engines work better, and then would go home to his loving wife and kids and invent still more things just for fun. <br />
  31. 31. Many of his after-work inventions could easily have led to business ventures elsewhere, but William seems to have been more interested in making things than fighting patent battles and all the other frenzy and frustration of running a company, like his bosses Mr Watt and MrBoultondid.<br />
  32. 32. William was quite happy where he was, working at the frontier of science and technology in Mr Watt’s sprawling steam pump factory. <br />Where else could he get a job working on the most advanced machinery of the age? <br />
  33. 33. William Murdock was more like the mythological backyard inventor <br />than anyone else I’ve ever come cross in my readings. His was the first gas-lit house in the world, fuelled by gases he prepared himself in his back yard. <br />
  34. 34. Amongst all the other things he made in his spare time and at his own cost <br />was a little toy no bigger than a dog or a cat, a tiny little steam engine with a piston cylinder no more than 2cm wide and just a few centimeters tall that sat on a set of wheels and had a handle at the front to adjust the direction of the wheels. <br />This is a picture of it here. No, not a reconstruction of it but the actual toy that he made, preserved in a museum today.<br />
  35. 35. It was the first real ‘steam engine’ as we would know it today, a locomotive. <br />William sometimes showed this off to his friends and neighbours, <br />a self-propelled steam engine whizzing round in circles <br />on the floor of his living room. <br />What on Earth was he going to do with a thing like this?<br />
  36. 36. End<br />dtcoulson@gmail.com<br />