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Michael A. Terrell wrote:
You also ignored Florida. A tricky one. It sort of fades out at the end, and unlike the Rio Grande it isn't a border. My understanding is that the border to Mexico is pretty heavily watched, whereas the crossings from Cuba are far less common. Anything that you think you might be able to tell that something better existed. :) Could you rephrase that for me please? Andy |
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Andy Champ wrote: Michael A. Terrell wrote: You also ignored Florida. A tricky one. It sort of fades out at the end, and unlike the Rio Grande it isn't a border. My understanding is that the border to Mexico is pretty heavily watched, whereas the crossings from Cuba are far less common. That is because boats from Cuba are stopped and the passengers returned to Cuba before they can land. Anything that you think you might be able to tell that something better existed. :) Could you rephrase that for me please? GEEZE! :) In other words, "You know there is something more expensive, but you know it isn't worth the price." -- http://improve-usenet.org/index.html aioe.org, Goggle Groups, and Web TV users must request to be white listed, or I will not see your messages. If you have broadband, your ISP may have a NNTP news server included in your account: http://www.usenettools.net/ISP.htm There are two kinds of people on this earth: The crazy, and the insane. The first sign of insanity is denying that you're crazy. |
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David Looser wrote...
Telephone exchange batteries were never for emergency use only. Rather the battery formed part of a UPS long before that term was coined. Initially it was normal to use a pair of batteries, one powering the exchange and the other on charge (either from mains or from a generator). This was known as "charge/discharge" working. Later float working became the norm (similar to the situation with car electrics when the engine is running). Running without the battery connected is not an option as the voltage regulation would go to pot, as would the ripple on the power bus. Thanks David, yes it was, as you say operating on float. I thought this arrangement was to cope with line power loss and was peculiar to the military requirements and didn't realise that it was an integral part of the system. Oops. I did take the battery off line while working on it. I wonder if this permanent connection would explain it long life. It may well still be there, surely due it's Long Service and Good Conduct medal by now. http://www.raf.mod.uk/bombercommand/s96.html "They also serve who only stand and wait" The batteries used in large automatic exchanges were far bigger than the one you mention. Individual cells could be 3ft square and 5 foot high, and there would be 25 of them. Thank heavens this was just a small one of about 100 lines. Fascinating to watch in operation cogs,wheels and relays clicking and whirring away like some Heath Robinson contraption. It's service log showed that all the soldered connections had been faithfully remade every two years or so, that must have been a long tedious job. I was always nervous around big high amp hour capacity batteries having been regaled in training with lurid tales of them exploding under deep discharge test. The maxim "If it starts making a noise, run away very fast", would have doubly applied to those dinosaurs you mention. -- Ken http://www.members.lycos.co.uk/buddyduck/ |
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Archimedes' Lever wrote:
On Tue, 30 Dec 2008 16:59:09 +0000, Andy Champ wrote: The fact that the groups posted here include uk.rec.audio No, the fact that some lame **** that knows very little about Usenet and has his news client altered to include a totally retarded "follow ups" line added to his retarded post, is why you are now seeing this thread. Not this time (although it's common). The original post from Eeyore had the same set of groups, and they are all at least slightly relevant. Not for example like the one I saw yesterday cross-posted to Surrey, Cycling and Transport when the subject is politics. Andy |
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On 2009-01-01, Greegor wrote:
I thought thermocouples used more exotic bimetals. Low cost ones made of steel/copper intrigue me. thermocouples for remote sensing do use exotic metals the metals are chosen to provide a large useful measurement range and a relatively high volts/kelvin output. Pretty much any two dissimilar metals will act as a thermocouple, copper and steel wire is cheap, and easy to work with. it's probably worth hiring a spot-welder for the construction - way easier than making thousands of soldered joins. I got about 5mv from a 6 copper + 5 steel thermopile when i heated one end with a lighter flame. the high thermal conductivity of copper is a disadvantage, possibly steel-nichrome may work better (not tested) But I'd also like to learn more about refrigerators that run on LP gas! http://en.wikipedia.org/wiki/Absorption_refrigerator seems to me you could run automotive AC off the exhaust (or possibly coolant) heat. |
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Jasen Betts wrote:
On 2009-01-01, Greegor wrote: I thought thermocouples used more exotic bimetals. Low cost ones made of steel/copper intrigue me. thermocouples for remote sensing do use exotic metals the metals are chosen to provide a large useful measurement range and a relatively high volts/kelvin output. Pretty much any two dissimilar metals will act as a thermocouple, copper and steel wire is cheap, and easy to work with. it's probably worth hiring a spot-welder for the construction - way easier than making thousands of soldered joins. The ITT Radio Engineer's Handbook has a list of various metals and the temp/voltage coefficients for various combinations. I got about 5mv from a 6 copper + 5 steel thermopile when i heated one end with a lighter flame. the high thermal conductivity of copper is a disadvantage, possibly steel-nichrome may work better (not tested) I think that the highest voltage you can get with hardware store materials would be nickel and nichrome as the two materials. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
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In article ,
Archimedes' Lever My Assistant: Zhang Heng wrote: On 2 Jan 2009 12:08:41 -0500, (Scott Dorsey) wrote: I think that the highest voltage you can get with hardware store materials would be nickel and nichrome as the two materials. Cheaper just to buy a calibrated thermocouple and a cheap meter that reads it. Harbor Frieght comes to mind. These are unfortunately made with metals that are chosen for consistency and reliability rather than the highest possible voltage. You _can_ buy a thermocouple stack intended for operating thermostats at the hardware store... those produce around a volt in a gas flame and they are usually nickel/nichrome thermocouples with maybe a hundred or so in series. You'd need at least four or five to run a radio, though. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
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On 2009-01-02, Archimedes' Lever wrote:
On 2 Jan 2009 12:08:41 -0500, (Scott Dorsey) wrote: I think that the highest voltage you can get with hardware store materials would be nickel and nichrome as the two materials. --scott Cheaper just to buy a calibrated thermocouple and a cheap meter that reads it. Harbor Frieght comes to mind. not for the intended purpose. |
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Scott Dorsey wrote:
I think that the highest voltage you can get with hardware store materials would be nickel and nichrome as the two materials. * Archimedes' Lever (Archimedes Plutonium Atom) wrote: APA Cheaper just to buy a calibrated thermocouple APA and a cheap meter that reads it. APA *Harbor Frieght comes to mind. For an emergency flame powered battery to run a radio? |
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