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Re: Train Physics Problem

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On 11/3/2015 12:19 PM, Fabian Russell wrote:
> On Tue, 03 Nov 2015 08:38:49 -0600, Odd Bodkin wrote:
>
>>
>> Not insignificant, but not huge either.
>>
>
> Yes, that is correct.
>
> This factor becomes even less significant in the everyday operating
> conditions of track gradients where the gravitational forces on
> a heavy train dwarf everything else.  A slight 2% grade can bring many
> trains to a complete halt.
>
> Trains also must dissipate all that huge energy as heat whenever they
> slow to a stop.  Most locomotives can use "regenerative" braking where
> the traction motors are run in reverse, using the magnetic field to
> produce current.  The current is then directed to resistive elements to
> produce waste heat.  Although it could be desirable, I doubt that it
> would be possible to use batteries to store that energy, much like
> in some automobiles.  AFAIK, no battery could absorb so much power
> so quickly.
>
> I wonder why no one else jumped on this question?  It is, after all,
> pure physics.  Most would rather rabidly bark at global warming issues
> which are not at all appropriate to this group.

I suspect that no one jumped on it because it's an elementary 
calculation from freshman physics. It's not like it's unexplored 
territory, unknown to engineers and physicists alike.

I think one pervasive problem on this newsgroup is that lots of people 
think that their posts are interesting and should draw lots of 
attention. It's the attention that's really craved, not that the problem 
is really all that interesting.

>
> But trains are the most efficient way to move stuff on land.  They
> can beat trucks on all counts (except for expeditious point-to-point
> delivery).  Any society that does not embrace trains is a losing society,
> yet currently railroad trackage is being abandoned at a rapid rate.
> Before too long, the US will possess only a few "backbone" rail corridors
> with all other transport being inefficient and extravagant trucks and planes.
>

Mile-for-mile you are correct.
But trains are less efficient than a container ship, which beats it for 
efficiency mile-for-mile by a factor of 20 or so.
So trains are fine for same-continent commerce, ships are vastly better 
for intercontinental trade.

Large-scale shipping requires both warehousing and large depots, which 
are expensive. They also cause a mismatch between stored supply and 
actual demand. Modern commerce is much more geared to just-in-time 
supply, which then favors point-to-point delivery when same-continent. 
This is why trucking is favored over rail. On the other hand, the sharp 
rise in international trade over the last few decades has bumped up 
intercontinental shipping, for which rail is useless.


-- 
Odd Bodkin --- maker of fine toys, tools, tables

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Train Physics Problem Fabian Russell <root@localhost.localdomain> - 2015-11-03 02:05 +0000
  Re: Train Physics Problem Fabian Russell <root@localhost.localdomain> - 2015-11-03 02:31 +0000
    Re: Train Physics Problem Fabian Russell <root@localhost.localdomain> - 2015-11-03 02:38 +0000
    Re: Train Physics Problem gillyshin <spectrum8@sincity.info> - 2015-11-03 04:38 +0000
      Re: Train Physics Problem gilber34 <fafa@invalid.com> - 2015-11-02 22:58 -0600
        Re: Train Physics Problem Fabian Russell <root@localhost.localdomain> - 2015-11-03 05:22 +0000
  Re: Train Physics Problem Odd Bodkin <bodkinodd@gmail.com> - 2015-11-03 08:38 -0600
    Re: Train Physics Problem Fabian Russell <root@localhost.localdomain> - 2015-11-03 18:19 +0000
      Re: Train Physics Problem Odd Bodkin <bodkinodd@gmail.com> - 2015-11-03 15:00 -0600
        Re: Train Physics Problem Fabian Russell <root@localhost.localdomain> - 2015-11-03 21:22 +0000
          Re: Train Physics Problem Odd Bodkin <bodkinodd@gmail.com> - 2015-11-03 16:55 -0600
            Re: Train Physics Problem Fabian Russell <root@localhost.localdomain> - 2015-11-03 23:19 +0000
        Re: Train Physics Problem Fabian Russell <root@localhost.localdomain> - 2015-11-03 21:31 +0000
          Re: Train Physics Problem Odd Bodkin <bodkinodd@gmail.com> - 2015-11-03 17:17 -0600
    Re: Train Physics Problem benj <none@gmail.com> - 2015-11-03 13:41 -0500
      Re: Train Physics Problem Fabian Russell <root@localhost.localdomain> - 2015-11-03 18:53 +0000
        Re: Train Physics Problem benj <none@gmail.com> - 2015-11-04 18:08 -0500
          Re: Train Physics Problem Fabian Russell <root@localhost.localdomain> - 2015-11-04 23:33 +0000
      Re: Train Physics Problem Odd Bodkin <bodkinodd@gmail.com> - 2015-11-03 15:10 -0600
        Re: Train Physics Problem Fabian Russell <root@localhost.localdomain> - 2015-11-03 21:48 +0000
          Re: Train Physics Problem benj <nobody@gmail.com> - 2015-11-04 02:45 -0500
  Re: Train Physics Problem "reber g=emc^2" <herbertglazier0@gmail.com> - 2015-11-03 09:19 -0800
    Re: Train Physics Problem "reber g=emc^2" <herbertglazier0@gmail.com> - 2015-11-04 15:15 -0800

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