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Rail transportation, train weight to passenger weight, reduce how much?

  1. Jul 31, 2011 #1
    If travelers sat on connected lawn chairs on wheels guided by rails pulled by a motor on wheels we might reduce the ratio of rail train weight to that of the weight of passengers carried.

    An Amtrak passenger train weighs about 200,000 lbs. and holds say 100, 200 lb. people, for a ratio of about 10 to 1.

    A light weight auto is about 2000lbs. and can hold five passengers for about 1000lbs. (those are likely crammed passengers) for a ratio of 2 to 1.

    Can we foresee lighter trains in the future where the weight ratio might reach 2 or smaller?

    Thanks for any help!
     
  2. jcsd
  3. Jul 31, 2011 #2

    SteamKing

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    If your passengers didn't mind sitting in the heat or cold, or in rainy or snowy weather, I don't see why you couldn't do what you have described. If they didn't want to have anything to eat or drink, or go to the bathroom, I'd say get rid of that bulky old train.

    On second thought, why do we have a railroad often running alongside a perfectly good highway? I say, get those lazy passengers out of their train seats and make them run to their destination!
     
  4. Jul 31, 2011 #3
    The first example was not practical, just curious how far weight could lowered while maintaining comfort and not raising the cost too far.
     
  5. Jul 31, 2011 #4
    There are several reasons why trains weight a lot more than just the passenger weight. Locomotives need to weigh quite a bit in order to pull a train, roughly 10% of the maximum weight train they will pull. Rail cars are also built heavy to provide the structural strength and stiffness to stand up to the service and to provide a safe structure in the event of a collision. As in many areas, much of these requirements are codified and there are no easy ways to avoid the resulting weight penalty.
     
  6. Aug 1, 2011 #5
    Weight is not a big issue on trains. It's not like they need to fly or anything, steel on steel wheels provide VERY low rolling resistance and, I'm sure as speeds get higher the air drag consumes the most energy.

    I suppose starting and stopping the things wastes more energy the heavier they are, but it would probably be cheaper and more effective to simply recover the energy with batteries or back into the grid.

    My point is, there are some vehicles (trains, ships) where high weight comes with a relatively low penalty. Might as well take advantage of this and indulge.
     
  7. Aug 1, 2011 #6
    This train was optimized for light weight:
    http://en.wikipedia.org/wiki/SNCF_TGV_Duplex
    but it still weighs 380t for 512 seats, or 742kg per seat, or 9 times the passenger weight.

    Not brilliant, is it?

    Weight is an issue for trains as well, because this limits their ability to travel in mountainous countries like Spain or South Korea or Italy - or worse, Austria, Switzerland...

    As for the locomotive's weight, spreading the propulsion among all cars is a solution, used for instance on ICE 3:
    http://en.wikipedia.org/wiki/ICE_3
    but still about 1t per seat.

    One of the reasons why cars are heavy is their need to sustain a contact with a wagon - something other professions would describe as a heavy collision, like a 76t wagon at 10km/h.
     
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