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Dave steam 2 (steam)(28)

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Part 2 - How steam 'works'

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Dave steam 2 (steam)(28)

1. 1. Steam Engines<br />A series of lessons <br />by David C<br />Dec 2010<br />
2. 2. Part 2<br />Steam pressure<br />
3. 3. Okay people,<br />Now in order to understand how steam engines work, <br />I think it’s important to understand how steam itself works. <br />
4. 4. Okay people,<br />Now in order to understand how steam engines work, <br />I think it’s important to understand how steam itself works. <br />Here’s a cube of water, 1cm along each side, and I’m going to boil it. Of course, steam is going to come off. <br />
5. 5. Okay people,<br />Now in order to understand how steam engines work, <br />I think it’s important to understand how steam itself works. <br />Here’s a cube of water, 1cm along each side, and I’m going to boil it. Of course, steam is going to come off. <br />But what I really want to know is, how much space will that cubic centimetre of water take up when it turns into steam?<br />
6. 6. Here it is, here.<br />
7. 7. Here it is, here.<br />If allowed to expand to its natural size, steam will occupy 1600 times as much space as it did when it was water.<br />
8. 8. That means a cube 11 or 12 times as big along each side.<br />
9. 9. That means a cube 11 or 12 times as big along each side.<br />It’s a bit like saying that the water in your mouth, if boiled, would fill up the whole of your head.<br />
10. 10. Now if all that steam was confined inside a much smaller box, the molecules would be pressed up hard against the walls, desperately trying to get out. <br />
11. 11. Now if all that steam was confined inside a much smaller box, the molecules would be pressed up hard against the walls, desperately trying to get out. <br />… and that means we could get it to do things for us.<br />
12. 12. Here’s an idea that Isaac Newton came up with, in the 1680s.<br />
13. 13. Here’s an idea that Isaac Newton came up with, in the 1680s.<br />You boil some water and let the steam vent out through a backwards-pointing jet, and drive the cart forwards.<br />
14. 14. Here’s an idea that Isaac Newton came up with, in the 1680s.<br />How well do you think it would have worked?<br />
15. 15. How about this idea from Archimedes, about 1800 or 1900 years ago.<br />
16. 16. How about this idea from Archimedes, about 1800 or 1900 years ago.<br />You pour some water into a cannon (or something shaped like a cannon),<br />…and then jam a projectile into the front of it, in such a way that the steam can’t get out until <br />
17. 17. How about this idea from Archimedes, about 1800 or 1900 years ago.<br />You pour some water into a cannon (or something shaped like a cannon),<br />…and then jam a projectile into the front of it, in such a way that the steam can’t get out until <br />Ka-Boom! <br />The thing explodes and shoots the projectile into your target.<br />
18. 18. How about this idea from Archimedes, about 1800 or 1900 years ago.<br />You pour some water into a cannon (or something shaped like a cannon),<br />…and then jam a projectile into the front of it, in such a way that the steam can’t get out until <br />Ka-Boom! <br />The thing explodes and shoots the projectile into your target.<br />Leonardo Da Vinci came up with the same idea in the 1500s.<br />
19. 19. But look at this! Here’s a steam cannon that was actually built in the US in the 1850s, just in time for Civil War.<br />
20. 20. You’ll be pleased to know it was never actually used in combat<br />
21. 21. A smaller version was under development during the second world war<br />
22. 22. Other things you can do with steam?<br />There was a fellow by the name of Hero, back in AD75, who had the idea of opening and closing temple doors by transferring water from one container to another. <br />
23. 23. Other things you can do with steam?<br />There was a fellow by the name of Hero, back in AD75, who had the idea of opening and closing temple doors by transferring water from one container to another. <br />The steamy part of the story is that he would have used steam pressure to push the water from container to container.<br />
24. 24. You could also use steam to play a musical instrument, <br />like a church organ.<br />
25. 25. You could also use steam to play a musical instrument, <br />like a church organ.<br />Steam would whistle up through the pipes.<br />Something like this was built in a church in Reims in 1125.<br />
26. 26. But the story of steam doesn’t really get going until the 1600s, <br />when people were struggling with the problem of getting water out of mines. <br />
27. 27. But the story of steam doesn’t really get going until the 1600s, <br />when people were struggling with the problem of getting water out of mines. <br />That will be the subject of my next lesson.<br />
28. 28. END<br />dtcoulson@gmail.com<br />