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Some DC and AC Motor History
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<br />[8)] <br /> <br /><font size="3"><font face="Georgia"><b>Overmod, I deserved the good whoopin' you gave me. Guity as charged about being really, really ignorant about "American technical history"; in my high school -- mind you, this was 30 years ago -- there was no course in engineering, nor even pre-calc; just physics that had to do almost entirely with the Newtonian system, next to nothing about electromagnetism, and nothin' at all about electronics, elec. engineering and so on. (If you think this thwarted would-be engineers and architects, by gum you're right--the error was eventually eliminated). But in my case, I left high school thinking that "Dynamo" was the name of a liquid laundry detergent. <br /> <br />Anywho, I bet you (and a couple of others on this post) can tell me (us) why the Chicago CTA's "L" cars exhibit almost no brake screech when they come to a halt at the station. In my dark past of READER reading, I think I remember the term "linear induction," in the sense that the some motors impelling forward motion could be used (in reverse??) to slow the train down to about 4 or 5 m.p.h., leaving the brakes free for relatively light duty, which I guess would mean not having to overcome so much inertia (impetus), the brakes just didn't wear out as quickly or in the same way--or perhaps a better Newtonian way to say that is that there was almost no need for the brakes to convert energy/momentum into energy/friction heat (??) <br /> <br />But since every time I make a suppository remark (?) I get busted[:0], and rightly so. Is there truth in the above paragraph, notwithstanding the fact that I probably abused about half a dozen terms? [:(] <br /> <br />Here's another thought for food--in railwaying, or interurbaning (CSS&SB), or light rail, does third-rail or "shoe" tend to make use of differing currents whether it draws from catenary or shoe; or whether it's AC or DC? (Is there a clever term that means "whether current is AC or DC"? "Modes," or something like that.) <br /> <br />Your point about AC in W. Europe is well taken -- my technical knowledge may have been okay at one time, but it stemmed from the "Magic Mountain" era of traction technology. [:I] <br /> <br />Certainly in Chicagoland the trend has been away from catenary wires whenever possible. The South Shore must have its overhead because it runs down the main streets of a couple of Indiana towns, but the sidings went catenary-free when the "Little Joe" 1947 motors were scrapped a number of years ago. And our beloved "Skokie Swift" -- actually just a tag of the old Chicago North Shore line to Milwaukee -- has gone totally third-rail in its Skokie domain, matching that of Evanston. (Alas, will I ever see "pan up" on the fly again?) <br /> <br />Other than the convenience factor--third rail doesn't blow down in a stiff wind or ice storm--is it really possible to make third-rail as safe as catenary? The Swift runs almost entirely at ground level in Skokie (it's mostly trenched in Evanston and no grade crossings). But Skokie is a built-up suburb with LOTS of grade crossing wig-wag + gates. <br /> <br />Ignoramus that I am, I myself would worry that my kid (or my neighbor's kid, or my dog) would contact the third-rail and perish. There are some swinging-gates at the pedestrian (usually sidewalk) level that close off human access to the tracks when the gate comes down, but the track is always energized, isn't it, even with no varnish in sight?. . . . <br /> <br />Also, several times a year someone falls (or sometimes is pushed) onto CTA third-rail and the results ain't pretty. Several years ago, in what must be the ultimate combination of stupid and pathetic, one young man arced in just the right way to fry himself while p***ing! <br /> <br />And finally, thanks for the link to GG-1 stats. Nothing makes learning more fun and fast than a compelling topic. <br /> <br />Now I think if I can learn how I'll post my own thread and stop mooching off the formidable Mookie's domain </b></font id="Georgia"></font id="size3">. . . [8] <br /> <br /><i><b><font color="red">al-in-chgo (4 blocks from L, 2 from commuter train). </font id="red"></b></i> <br />
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