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| Re: LIRR: Third rail vs. catenary (352654) | |||
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Re: LIRR: Third rail vs. catenary |
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Posted by Brighton Private on Wed Dec 13 10:19:11 2006, in response to Re: LIRR: Third rail vs. catenary, posted by Jeff H. on Wed Dec 13 03:59:06 2006. why would you want to?For the LIRR, it would resolve the problem of "gapping out" for push-pull trains, a major obstacle to providing thousands of commuters a one-seat ride into Penn Station. It is not clear what, if anything, it would have done for the NY subways, though there must be some operational advantages even for urban subway systems because it is being widely used including, as noted, in Tokyo. Speaking of gapping out, a question: why were LIRR dual-mode locos built for third rail at all? Why couldn't they run diesel as far as Harold, and then shift to overhead AC for the rest of the run into Penn Station? It can't be that switching from DC to AC is a problem, as the MN New Haven Division trains do it all the time. Assuming this could be accomplished, one wouldn't need a loco on each end of the train and the LIRR would be able to provide more one-seat serviced, as had been promised to riders of the diesel lines when the DM's were ordered. I'm sure there's a sensible answer -- I'm not saying the LIRR people are idiots -- I'm just curious to know what it is. (It can't be a "cab forward" problem -- wayside indicators could tell the engineer when to raise the pantograph on inbound trains, for which control provision could be provided in the cab.) I might have thought the problem related to taking AC rather than DC power, but modern diesels generate AC propulsion power anyway. |
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