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From: Dan_Bower%RPI-MTS.Mailnet@MIT-MULTICS.ARPA
Newsgroups: net.railroad
Subject: Ties
Message-ID: <1653@brl-tgr.ARPA>
Date: Mon, 23-Sep-85 11:00:06 EDT
Article-I.D.: brl-tgr.1653
Posted: Mon Sep 23 11:00:06 1985
Date-Received: Wed, 25-Sep-85 10:54:56 EDT
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Concrete ties have a number of advantages.  They mass 3 to 4 times that of
a wood tie, giving the track far greater inertia.  This makes it harder
for a train to knock it out of alignment.  With the quality of concrete
used today, life estimates range from 40 to 50 years.  (This compares to
30 years for a wood tie.  Both figures are for ideal conditions.  Poor
drainage, extremely heavy traffic, etc. can cut the life of any tie in
half or less.)
Also, because of the way a concrete tie deteriorates (it's either broken
or it ain't) you can use a wider spacing between them than with wood ties.
With wood, you expect a gradual deterioration and compensate by putting in
more than is needed if they performed like new for their entire lives.
19 1/2" to 22" is typical on mainlines for wood ties.  With concrete,
30" is common, as a 30" inch spacing is adequate for support and gauge, IF
all the ties are up to snuff.

There are some disadvantages with concrete ties.  One, you can't mix them
with wood.  Because of concrete's greater rigidity, the concrete ties in
mixed track would quickly end up supporting all the load of the train.
If you want to use concrete, you have to replace all the ties all at once.
Concrete is a lot harder to handle.  Two guys can't just grab one and walk
away with it like they can with wood.  Concrete ties make for more ridgid
track, giving a noiser, rougher ride than wood ties.  (There are special
cushion pads to go between the rail and tie, at an extra cost, of course.)
Finally, going with concrete requires a very large capital expendature.
As you may know, new capital is scarce on most railroads these days.

Also, most concrete ties are not adjustable for gauge.  On curves, rail
will wear allowing a widened gauge.  With wood ties, you pull the spikes,
plug the holes, move the rail into gauge and spike it back down.  With
concrete, you only have the choice of transposing the rail or swapping it
with the low side of the curve.  Both alternatives require immediate
rail grinding to undo the high side wear and low side deformation.

Re: rail life
It depends on where the rail is, what steel it's made of, and what runs on
it.  On lightly used branch lines, rail lasts (practically) forever.
On heavy mains, rail on tangents may last as long as 35 to 45 years if
the track is kept in good surface.  On curves, the faster the trains go
the more they will abrade the high side rail.  They heavier they are,
the more they deform the low side.  In the worst cases, rail gets worn
faster than the traffic can work harden the surface, and it wears out in
3 or 4 years.  If the rail was heat treated or of a special alloy, you
might get 50% to 100% more life out of it.  There are also some asymetrical
grinding tricks that can prolong rail life on moderate curves.  These
involve grinding the high rail so that the wheel is in contact close to
the flange (where the radius of the wheel is greatest) and grinding the
low rail so the wheel rides on the outside of the tread.  This has a
slight self steering effect which can double rail life on curves up to
2 to 3 degrees.  Curve lubrication has been used for some time.  This
does reduce abrasive wear, but it reduces traction and has been observed
to increase deformation.  (The problem with reducing traction is that if
the engine slips, the engineer drops sand.  The grease holds the sand
to the rail, greatly increasing abrasive wear.  Some railroads with
double track lines only put curve greasers on the track where traffic is
mostly downgrade.)