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Captain Simion

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  • Low Tech Greenhouse Automation : Cooling, Warming, Watering

    I dislike being wrong, but I was wrong. I re-read about the freezing/pipe-bursting process and now see how it works. Ice can form a plug, and, if there is no air space, the remaining liquid water has no alternative but to displace some metal. I'm still right about the forces involved, however. You need a tight piston to contain the water. Someone did nice machining on those brass parts - they could make you a piston with an o-ring groove. The "water motor" has the perfect temperature curve for this job!

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  • Low Tech Greenhouse Automation : Cooling, Warming, Watering

    Three thoughts: A) Your oogoo experiments and examples are wonderful. Keep it up.B) The problem with the freezing-water-in-a-cylinder-with-piston device is that water expands in all three directions when it freezes. This is why it breaks pipes; it not only pushes the excess volume back up the pipe like a piston - it also pushes out sideways against the walls. It would not immediately break the copper pipe, unlike what it does to steel pipe, but repeated freezing/thawing would stretch the pipe until it swelled and cracked. (I had a house in Ohio where this happened.) Although water expands 10% by VOLUME upon freezing, it only expands by the cube root of 1.10 or 3.2% in EACH DIRECTION (an approximation). The piston moved all right, but only by 3.2%. C) The coefficient of thermal expansion …

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    Three thoughts: A) Your oogoo experiments and examples are wonderful. Keep it up.B) The problem with the freezing-water-in-a-cylinder-with-piston device is that water expands in all three directions when it freezes. This is why it breaks pipes; it not only pushes the excess volume back up the pipe like a piston - it also pushes out sideways against the walls. It would not immediately break the copper pipe, unlike what it does to steel pipe, but repeated freezing/thawing would stretch the pipe until it swelled and cracked. (I had a house in Ohio where this happened.) Although water expands 10% by VOLUME upon freezing, it only expands by the cube root of 1.10 or 3.2% in EACH DIRECTION (an approximation). The piston moved all right, but only by 3.2%. C) The coefficient of thermal expansion of the PTFE piston is more that 5 times greater than that of copper, so as the temperature goes down, the piston will get looser in the cylinder. Besides, the force generated by the expansion of water freezing is enormous; it will overcome any and all sticktion between the parts. Remember that it breaks steel pipes.

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  • Captain Simion commented on Phil B's instructable 555 Capacitor Tester
    555 Capacitor Tester

    See Elektor magazine July/August 1977 "Digital Capacitance Meter with 555 Timer" by J. Borgman .

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  • The Gutenberg Project https://www.gutenberg.org/has over 58,000 books already scanned and indexed that one can download for free. Nothing to shelve or return. Please donate.

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  • I'm interested in making a similar table, and it must be very flat (planar, as opposed to level). How did you determine that the result was flat within a millimeter or two? Did you use that method to determine which part of your living room floor was flat enough to work on, or that the garage floor was not? Unfortunately, if your frame pieces are not straight, bolting them to the top will warp the top. How did you check the frame pieces for straightness? A suggestion for construction: if you are going to double up the 2x4s for the frame, stack them on edge so they total "8" inches tall, then glue and bolt them together. Use epoxy or urethane. This will result in a beam that is eight times stiffer than a single 2x4 and four times stiffer than two 2x4s side-by-side. If you don't…

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    I'm interested in making a similar table, and it must be very flat (planar, as opposed to level). How did you determine that the result was flat within a millimeter or two? Did you use that method to determine which part of your living room floor was flat enough to work on, or that the garage floor was not? Unfortunately, if your frame pieces are not straight, bolting them to the top will warp the top. How did you check the frame pieces for straightness? A suggestion for construction: if you are going to double up the 2x4s for the frame, stack them on edge so they total "8" inches tall, then glue and bolt them together. Use epoxy or urethane. This will result in a beam that is eight times stiffer than a single 2x4 and four times stiffer than two 2x4s side-by-side. If you don't bolt them together, the 8 inch beam will only be twice as stiff as the bolted one.

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