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From: Morten Reistad on 9 May 2010 08:51 In article <hrtg1d$o2$2(a)news.eternal-september.org>, Charles Richmond <frizzle(a)tx.rr.com> wrote: >Walter Bushell wrote: >> In article <hrqoft$enh$2(a)news.eternal-september.org>, >> Charles Richmond <frizzle(a)tx.rr.com> wrote: >> >>> Yeah!!! Where the hell would the world be today without the >>> three-phase electric motor??? All the "heavy industry" plants rely >>> on this workhorse, and Tesla invented it. >> >> Ah, I remember a exhibit in the Smithsonian museum in Washington D.C. of >> a steam powered factory. The ceiling was entirely belts, because every >> machine was belt powered. >> > >Sure, a steam powered factory. You can sort of make that work for >weaving machines. But think of a car assembly line using this time >of steam powered factory with belts transferring the motion... A majority of our electricity generation is steam powered. Almoast all coal and most nuclear power generators heat water to somewhere around 250 degrees C, and send the steam down into a turbine, with generator attached. Tesla would recognise this; as the stator generates three phase power, and the current in the rotor is the controlling factor through a simple feedback mechanism. This then has to feed back to the steam pressure. Nowadays we use transistors to control the rotor current, tesla would have had to use a resistor network. -- mrr
From: Morten Reistad on 9 May 2010 08:56 In article <proto-CA5809.10044006052010(a)news.panix.com>, Walter Bushell <proto(a)panix.com> wrote: >In article <timstreater-0EB4E9.14160506052010(a)news.individual.net>, > Tim Streater <timstreater(a)waitrose.com> wrote: > >> Newtons laws are a good example of this. They have not been >> "invalidated" by Einstein's Relativity. For most purposes, Newton's laws >> will allow you to calculate trajectories through space quite adequately. >> But if you want to calculate the orbit of Mercury around the Sun with >> great precision for the next umpty-ump years, better use Einstein. >> Newtons Laws can be derived from Einstein anyway, as a special case >> where gravity is weak (i.e. not near a body the mass of the Sun or >> greater). > >And great accuracy is not needed. There is a relativistic effect that >has to be accounted for in the case of communication satellites. GPS satellites have to use a lot of relativity to obtain their time/space accuracy. Geostationary satellites have to use a little of relativity to compensate correctly for the drag effects of earth, moon and sun. Other satellites can get by pretty well with newtonian mechanics, including lunar missions. -- mrr
From: Geoffrey S. Mendelson on 9 May 2010 11:54 Morten Reistad wrote: > Geostationary satellites have to use a little > of relativity to compensate correctly for the drag effects of earth, > moon and sun. Actually most if not all geosynchronous satellites don't correct at all for any of that. As they start to drift off, they are given commands by a ground control station to get back to where they belong. How the ground control station calculates what to do is another matter. Obviously they are not going to refuel them, so it is very important to get it right the first time. Over the years, several satellites have been "reparked", or moved. In the late 1980's or early 1990's all the C band satellites where moved either closer together or farther apart and new ones inserted in the middle. There are also a bunch of 1980's Ku band TV satellites pointed twoard Europe that were no longer in use and someone was trying to move and retask them. A few years ago there were proposals to make them one big satellite radio network, covering all of Europe, but I have no idea of what happened to them. Geoff. -- Geoffrey S. Mendelson, Jerusalem, Israel gsm(a)mendelson.com N3OWJ/4X1GM New word I coined 12/13/09, "Sub-Wikipedia" adj, describing knowledge or understanding, as in he has a sub-wikipedia understanding of the situation. i.e possessing less facts or information than can be found in the Wikipedia.
From: AES on 9 May 2010 12:43 In article <bonib7-fjo.ln1(a)laptop.reistad.name>, Morten Reistad <first(a)last.name> wrote: > >> Ah, I remember a exhibit in the Smithsonian museum in Washington D.C. of > >> a steam powered factory. The ceiling was entirely belts, because every > >> machine was belt powered. Brings back a memory of taking some work for a Stanford University research project to a small, very funky job shop, located up on a hillside in South San Francisco, that was set up in exactly this way, in the late 1950s or early 1960s. Said memory is fuzzy at this point, but I think there were maybe 6 or 8 parallel drive shafts 20 to 30 feet long and 5 or 6 feet apart mounted in bearings hanging just under the ceiling, with one of them driven by a foot-wide fabric belt running up from a prime mover on the shop floor, and this motion then being transferred from shaft to shaft via additional belts. Smaller belts then transferred this motion down to individual lathes and other machine tools located all around the room. I really don't think the prime mover was steam, however -- I think it was just some big antique-looking electric motor. What do you call the process where you position a circular disk of sheet metal in a lathe, spin it about an axis perpendicular to the center of the disk, and then push on the spinning disk with a tool the size of baseball bat with a smooth metal cap on one end to shape the disc into a conical dish shape? That's what we were getting done -- though I can't at this point remember why.
From: Anne & Lynn Wheeler on 9 May 2010 13:39
"Geoffrey S. Mendelson" <gsm(a)cable.mendelson.com> writes: > Actually most if not all geosynchronous satellites don't correct at all > for any of that. As they start to drift off, they are given commands by > a ground control station to get back to where they belong. i.e. they "wear out" when they run out of propulsion to correct drift. hsdt http://www.garlic.com/~lynn/subnetwork.html#hsdt had transponder on sbs4 ... even got to attend its launch on 41d http://www.nasa.gov/mission_pages/shuttle/shuttlemissions/archives/sts-41D.html had done two different sets of custom specified earth station hardware (with two different vendors). one of the vendors mentioned that they had been approached by the large telco and asked if the vendor would build a duplicate to our specifications for them (apparently an example of standard industrial espionage). one of the pains was all corporate stuff (both terrestrial and satellite) had to be encrypted ... at one point in the mid-80s there was claim that the internal network had half (or more) of all the link encryptors in the world. the problem i had was getting T1 and higher speed encryption (aka lots of stuff out their for slower speeds). past posts mentioning internal network http://www.garlic.com/~lynn/subnetwork.html#internalnet past reference to trying to do something of my own and discovering (that at least in mid-80s) there were three kinds of crypto: http://www.garlic.com/~lynn/2008h.html#87 New test attempt http://www.garlic.com/~lynn/2009l.html#14 August 7, 1944: today is the 65th Anniversary of the Birth of the Computer misc. past posts mentioning 41d: http://www.garlic.com/~lynn/2000b.html#27 Tysons Corner, Virginia http://www.garlic.com/~lynn/2002p.html#28 Western Union data communications? http://www.garlic.com/~lynn/2003j.html#29 IBM 3725 Comms. controller - Worth saving? http://www.garlic.com/~lynn/2003k.html#14 Ping: Anne & Lynn Wheeler http://www.garlic.com/~lynn/2004b.html#23 Health care and lies http://www.garlic.com/~lynn/2004o.html#60 JES2 NJE setup http://www.garlic.com/~lynn/2005h.html#21 Thou shalt have no other gods before the ANSI C standard http://www.garlic.com/~lynn/2005q.html#17 Ethernet, Aloha and CSMA/CD - http://www.garlic.com/~lynn/2006k.html#55 5963 (computer grade dual triode) production dates? http://www.garlic.com/~lynn/2006m.html#11 An Out-of-the-Main Activity http://www.garlic.com/~lynn/2006m.html#16 Why I use a Mac, anno 2006 http://www.garlic.com/~lynn/2006p.html#31 "25th Anniversary of the Personal Computer" http://www.garlic.com/~lynn/2006v.html#41 Year-end computer bug could ground Shuttle http://www.garlic.com/~lynn/2007p.html#61 Damn http://www.garlic.com/~lynn/2008m.html#19 IBM-MAIN longevity http://www.garlic.com/~lynn/2008m.html#20 IBM-MAIN longevity http://www.garlic.com/~lynn/2008m.html#44 IBM-MAIN longevity http://www.garlic.com/~lynn/2009i.html#27 My Vintage Dream PC http://www.garlic.com/~lynn/2009k.html#76 And, 40 years of IBM midrange http://www.garlic.com/~lynn/2009o.html#36 U.S. students behind in math, science, analysis says http://www.garlic.com/~lynn/2010c.html#57 watches -- 42yrs virtualization experience (since Jan68), online at home since Mar1970 |