| 21. | These are simple poppet valves, operating by direct float action and sealing against the upper valve seat.
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| 22. | The rocket is fired when the computer sends direct current through a small electromagnet that opens the poppet valve.
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| 23. | Early designs used the D slide valve but this has been largely superseded by Piston valve or Poppet valve designs.
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| 24. | Use of poppet valves also increased the speed because they gave very accurately-timed steam delivery to the cylinders.
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| 25. | The poppet valves were not a great success and they all reverted to piston valve engines between 1931 and 1934.
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| 26. | The innovation trialled on # 5699 was its use of Caprotti valve gear, a poppet valve gear invented in Italy.
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| 27. | With no inlet pressure, the spring above the diaphragm pushes it down on the poppet valve, holding it open.
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| 28. | The ball lock valves may be unscrewed using wrenches to allow further cleaning or replacement of O-rings or poppet valves.
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| 29. | James Watt was using poppet valves to control the flow of steam into the cylinders of his beam engines in the 1770s.
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| 30. | Intake and exhaust poppet valves could be moved and controlled independently of each other, allowing for better control of the cycle.
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