From: S_KOEHLER@iravcl.ira.uka.de (|S| Tobias Koehler)
Newsgroups: rec.railroad
Subject: Re: ? about engine sets
Date: 25 Jan 1993 15:24:02 GMT
Organization: University of Karlsruhe (FRG) - Informatik Rechnerabt.
Distribution: world
NNTP-Posting-Host: irav1.ira.uka.de
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In <1993Jan23.141936.22629@netcom.com> tssmith@netcom.com writes:

> In article <1jp1qtINN4as@grapevine.EBay.Sun.COM> maral@repare.EBay.Sun.COM writes:
> > My son asked me a question the other day and I couldn't answer him
> > so I thought I would tap the knowledge of all you experts.  The
> > question is why do trains utilize various engine types when pulling
> > a string of cars and why do some point forwards and some backwards?
> > I kind of would like to know myself.  A 10 year old and 36 year old kid
> > appreciates your response.
> 
> Sounds like you're a newcomer here.  Welcome, and I'll try to keep
> the answers simple.  There are three things going on:
> 
I live in Central Europe. Here the things are quite different ....

> First, as you noted, most freight (and some passenger) trains are
> pulled by more than one engine.  Out west, it's not uncommon to see
> five or more engines at the head of a train, and sometimes several
> more pushing at the end, or pushing and pulling in the middle.  All the
> locos (units) are usually controlled from the front cab.
 
Here in Europe, double traction is regarded uneconomic.
In Germany only some heavy freight trains are pulled by two electric locomo-
tives. On Diesel lines you can often see two locomotives pulling freight or
passenger trains. Sometimes, when locomotives have to be transported from
one place to another, there are two locos on the train, but only the one in
front is pulling, and the other is switched off (pantograph down).
On mountain lines in Switzerland one can often see one 620 (6 axles) pulling
a freight train together with one 430 (4 axles). Very heavy trains have one
620 in front and another in the middle.

> Second, locomotives, unlike automobiles, run just as well in reverse
> as in forward.  This is true of steam and electric locomotives as
> well as diesels.  The thing that determines the natural direction of

No. Steam locomotives (except tender locomotives) usually could run faster
forward than backward. There had to be drivers in all the locomotives at
that time.

> travel is the location of the engineer's cab.  Most diesel
> locomotives have the cab up front.  Some older electric locomotives
> had a central cab, and these could run "naturally" in either
> direction.
 
Here most locomotives have two cabs, one at each end. Shunting and branch
line engines often have a central cab. So all these locomotive can run freely
in both directions. Electric locomotives are often built perfectly symmetric.
Only some special locomotives, like the ones used in the urban railway
(S-Bahn) in Zuerich, or the special locomotives permanently coupled to high
speed trains like the TGV or ICE (here we have double traction as well), have
one cab.
In Great Britain some types of locomotives have one streamlined and one
flat end, both with a cab. They are faster when they run into the streamlined
direction.

> The third thing is that when a locomotive, or a set of locomotives,
> gets to the end of the run, or to some "division point" in the run, it
> then usually goes back the other way on a different train.  So if you
> have, say, two diesels coupled back end to back end, it's very simple
> to uncouple them from the train they were pulling, switch them onto a
> parallel track, and couple them to a new train.  Now the back becomes
> the front, and the new crew uses the former back cab.  But if you had
> to turn the engines around, you'd need a lot of extra track (a loop
> or a "Y"), requiring more real estate and more complicated switching
> operations.

Are there still turning plates used in America for turning Diesel locomotives?
Here in Europe most of them are not in service any more.
 
> Another example of railroads' saving time and space are the so-called
> "push-pull" commuter trains.  These have a single diesel locomotive
> at the front of the train, usually facing out of the main city
> station, and a cab built into the end of the last car of the train. 
> When the train gets to the end of its "outbound" run, the engineer
> can just go back to the cab in the last car, and run the train back
> into the city by controlling the locomotive remotely from there.  The
> locomotive is now running in reverse, pushing the train.

This principle is also used at the Swedish X2000, the British IC250 and the
future German ICE2 half-trains. And it is very common for commuter trains
in whole Europe.
 
> As far as different types of locomotives on a train, this is less
> common.  (Don't be misled by the color or marking of the
> locomotives.  It's common now for railroads to use "pooled" power, so
> you might see, say, a bright yellow Union Pacific unit in the middle
> of some blue Conrail units, pulling a train somewhere east of
> Chicago--not UP territory.)  But a railroad can mix locomotives with
> some freedom, when needed.

Is there an american standard for the cables that transmit the signals from
the front cab to the other locomotive(s)? This is one of the problems that
we have when unifying the East and West German railway. Two incompatible 
standards have been developed when the country was separated.
There are even more standards in the other countries ....

regards

-=- tobi -=-
Newsgroups: rec.railroad