m7zanr160s Posted January 5, 2010 Share #1 Posted January 5, 2010 This might be common sense, but I just don't know for sure. It's not like you can go touch and see. Bottom contact, I can see, but what about top contact. Is it spring-loaded to keep it in contact with the rail or is it heavy enough to ride along just fine? Link to comment Share on other sites More sharing options...
INDman Posted January 5, 2010 Share #2 Posted January 5, 2010 Yes they are, they have a force of about 30 lbs pushing down on them so they provide a reliable connection to the 3rd rail. Link to comment Share on other sites More sharing options...
Fan Railer Posted January 5, 2010 Share #3 Posted January 5, 2010 This might be common sense, but I just don't know for sure. It's not like you can go touch and see. Bottom contact, I can see, but what about top contact. Is it spring-loaded to keep it in contact with the rail or is it heavy enough to ride along just fine? the tiny thing isn't a quarter the size of my keyboard and won't weight more than 5-6 lbs. for closeup images, go here: http://www.nycsubway.org/cars/yards_coney_truck.html Link to comment Share on other sites More sharing options...
SubwayGuy Posted January 5, 2010 Share #4 Posted January 5, 2010 Yes it's spring loaded. I don't have the exact tension range sitting around offhand at the moment however. It must be fairly precise because if the spring is too loaded, the shoes and 3rd rail will wear too quickly...if too light, the shoe will not maintain perfect contact with the rail as the car moves causing electrical arcing Link to comment Share on other sites More sharing options...
INDman Posted January 5, 2010 Share #5 Posted January 5, 2010 Yes it's spring loaded. I don't have the exact tension range sitting around offhand at the moment however. It must be fairly precise because if the spring is too loaded, the shoes and 3rd rail will wear too quickly...if too light, the shoe will not maintain perfect contact with the rail as the car moves causing electrical arcing It's about 30 lbs, at least thats what it is on the NTTs. "the tiny thing isn't a quarter the size of my keyboard and won't weight more than 5-6 lbs." They are bigger then that. Once you have one in your hand you see how big they are. Also they are heavy, maybe 10 or more lbs. Link to comment Share on other sites More sharing options...
Joe Posted January 5, 2010 Share #6 Posted January 5, 2010 Is the tension constant or adjustable? Link to comment Share on other sites More sharing options...
INDman Posted January 5, 2010 Share #7 Posted January 5, 2010 Is the tension constant or adjustable? Constant, there is a spring that pushes it down. Link to comment Share on other sites More sharing options...
Fan Railer Posted January 5, 2010 Share #8 Posted January 5, 2010 It's about 30 lbs, at least thats what it is on the NTTs. "the tiny thing isn't a quarter the size of my keyboard and won't weight more than 5-6 lbs." They are bigger then that. Once you have one in your hand you see how big they are. Also they are heavy, maybe 10 or more lbs. lol, ok. maybe half the size of my keyboard now that i think about it... Link to comment Share on other sites More sharing options...
Joe Posted January 5, 2010 Share #9 Posted January 5, 2010 Constant, there is a spring that pushes it down. Well, even with a spring can't one adjust the preload on the spring, thereby changing tension? Link to comment Share on other sites More sharing options...
INDman Posted January 5, 2010 Share #10 Posted January 5, 2010 Well, even with a spring can't one adjust the preload on the spring, thereby changing tension? I'm not 100% sure, but I can check on that tom. Link to comment Share on other sites More sharing options...
Art Vandelay Posted January 5, 2010 Share #11 Posted January 5, 2010 30 pounds sounds about right. It isn't that hard, nor that easy to push against the spring. Yes, I have done it. No, it was not on electrified tracks. (Actually, I don't think it was on any tracks, and I don't remember what type of car the truck was from.) Link to comment Share on other sites More sharing options...
Joe Posted January 5, 2010 Share #12 Posted January 5, 2010 Yes, I have done it. No, it was not on electrified tracks. I would certainly hope not! Link to comment Share on other sites More sharing options...
m7zanr160s Posted January 5, 2010 Author Share #13 Posted January 5, 2010 Yeah, cool. Makes sense about the wear-and-tear thing, cause I was wondering if they get replaced because of friction. Kinda like my kicks after a year...year...no, a couple months of balling on concrete. That rubber goes fast, but third rails are pretty smooth, plus steel, so... Appreciate the answers, thanks. Link to comment Share on other sites More sharing options...
Joe Posted January 5, 2010 Share #14 Posted January 5, 2010 Also worth noting here is that third rail shoes have shear joints. That way if they happen to strike some trackside furniture, the shoe will break off instead of wrecking whatever it strikes (though i'm sure the furniture won't be unscathed). Link to comment Share on other sites More sharing options...
SubwayGuy Posted January 5, 2010 Share #15 Posted January 5, 2010 Yeah, cool. Makes sense about the wear-and-tear thing, cause I was wondering if they get replaced because of friction. Kinda like my kicks after a year...year...no, a couple months of balling on concrete. That rubber goes fast, but third rails are pretty smooth, plus steel, so... Appreciate the answers, thanks. Actually most subway car parts that are subject to friction have a condemning line or some sort of inspection point that where they fail, they are replaced. So if a third rail shoe is worn to a certain point, it's time to replace it. Link to comment Share on other sites More sharing options...
INDman Posted January 5, 2010 Share #16 Posted January 5, 2010 Also worth noting here is that third rail shoes have shear joints. That way if they happen to strike some trackside furniture, the shoe will break off instead of wrecking whatever it strikes (though i'm sure the furniture won't be unscathed). If it his something metal, usually it will vaporize what it hit. Link to comment Share on other sites More sharing options...
Joe Posted January 5, 2010 Share #17 Posted January 5, 2010 If it his something metal, usually it will vaporize what it hit. They are designed to break though, correct? I'm 99% sure I heard an MNR employee say that at the last Croton open house. Link to comment Share on other sites More sharing options...
INDman Posted January 5, 2010 Share #18 Posted January 5, 2010 I think so, but Im sure it takes a hell of an object to do that. Link to comment Share on other sites More sharing options...
SubwayGuy Posted January 5, 2010 Share #19 Posted January 5, 2010 They are designed to break though, correct? I'm 99% sure I heard an MNR employee say that at the last Croton open house. Would have to inspect the specific shoes to tell. New tech shoes are specifically designed to be smaller than their SMEE counterparts though. And yes at 10,000 amps something that "completes the circuit" with the shoe and a dead short to ground can easily be vaporized Link to comment Share on other sites More sharing options...
metsfan Posted January 5, 2010 Share #20 Posted January 5, 2010 And yes at 10,000 amps something that "completes the circuit" with the shoe and a dead short to ground can easily be vaporized 10,000 amps is a lot of current, at 600-650 volts direct current, if you touch metal to metal you will get a huge shower of sparks and bright light. Arc furnaces range from 3,000 to 400,000 amps at something like 40,000 volts DC, so yea, you'd get burned if you survived & if metal touches it, either vaporize or melt. - A Link to comment Share on other sites More sharing options...
St Louis Car 09 Posted January 5, 2010 Share #21 Posted January 5, 2010 Given that you actually survive.What are the chances of surviving a third rail shock?:confused: Link to comment Share on other sites More sharing options...
INDman Posted January 5, 2010 Share #22 Posted January 5, 2010 Given that you actually survive.What are the chances of surviving a third rail shock?:confused: Very low. Link to comment Share on other sites More sharing options...
St Louis Car 09 Posted January 5, 2010 Share #23 Posted January 5, 2010 Very low.(Pops out of nowhere) TOASTY!!!!B) Link to comment Share on other sites More sharing options...
INDman Posted January 5, 2010 Share #24 Posted January 5, 2010 (Pops out of nowhere) TOASTY!!!!B) And very smelly. Link to comment Share on other sites More sharing options...
SubwayGuy Posted January 6, 2010 Share #25 Posted January 6, 2010 Given that you actually survive.What are the chances of surviving a third rail shock?:confused: Not too good, since it's the amps and not the voltage that ultimately do you in and 10,000 amps is a lot Link to comment Share on other sites More sharing options...
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