NetNews Usenet Archive 1993 #3/NN_1993_3.iso/spool/rec/railroad/10831

Internet Message Format | 1993-01-22 | 3.4 KB

From: [e-mail] (Jobst Brandt)
Date: Fri, 22 Jan 1993 01:51:01 GMT
Subject: Re: European track
Message-ID: <[e-mail]>
Organization: Hewlett-Packard Laboratories, Palo Alto, CA
Path: sparky!uunet!usc!sdd.hp.com!hpscit.sc.hp.com!hplextra!hplred!jbrandt
Newsgroups: rec.railroad
References: <[e-mail]>
Lines: 58

Andrew Waugh writes:

> To answer the original question, however, it was definitely U.S.
> railroad practice (at least until the introduction of CWR) to
> provide expansion gaps at the end of each rail length and to allow
> rails to expand and contract as necessary.

The use of clearance between rails resulted from a misunderstanding
of rail buckling in hot weather.  In fact it occurred on any average
day as well except that the symptoms pointed toward thermal
expansion.  You will notice that all new rail laid these days is
longitudinally anchored at as many as every other crosstie in some
cases.  The cause of rail buckling in the days after anglebars with
spike holes ended (long ago) rails moved relatively freely under the
rolling action of trains similarly to cookie dough under a rolling
pin if you roll only one way.  Rail piles up at the next switch
because these cannot move.  Buckling invariably occurs at such a
rail feature.

> There is actually a subtle difference between angle bars and
> splice bars.  Splice bars are flat steel bars which lie against
> the web of the rail.  Angle bars, a latter development, are
> similar to splice bars but the bottom angles out and sits on the
> foot of the rail.  This makes the joint more rigid. In Victoria,
> we use 'fishplate' for both types.

Neither kind of angle bar makes a strong joint as is evident from
the depression of rails at rail joints.  The rail profile is a fairly
efficient I-beam and since the bending stiffness of a such a beam is
roughly proportional to the cube of its height, angle bars that have
a height of about half the rail are about eight times more flexible
than the rail.  The stress at this junction is severe and highly
concentrated.  I am amazed that any mainline is still operated with
this kind of rail today.  The local "high iron" of this type looks
like so many arched rails with hinges at their ends.  This is a
common sight in telephoto shots down the track.

> According to the PWI book, during a typical yearly routine for a
> track gang, they would spend about 3 weeks greasing the
> fishplates.  In addition to greasing the fishplates and bolts, the
> gang would check the ends of the rails for cracks, burns, etc.
> They would also adjust the expansion gaps if necessary.

This must be from the days of undocumented foreign labor when such
useless activities were the norm.  The far greater problem was in in
some cases still is maintaining track circuits with rail bonds.
The best solution to this was the old method with two rigid wire
inserted through the neutral axis of the rail web beyond the ends of
the angle bar with a 3/4 coil for elasticity and threaded behind the
angle bar.  These seldom failed but were inordinately expensive.
Modern signaling avoids track circuits anyway.

Welded rail, today is generally joined at a central welding site and
brought to the installation site for in place welding that is
still done by the Thermit or Boutet method although mobile
resistance butt welding machines are the preferred method.

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