steam loco question

nw-mailing-list at nw-mailing-list at
Thu Jun 29 23:55:24 EDT 2006

I'll let someone else address the wreck, but the change in superelevation I
can address as an add-on to my previous contribution.

If you think about it, it's intuitively obvious (and not hard to calculate)
that a particular combination of curvature and superelevation is going to
have only one ideal speed (ignoring for the moment differing locations of the
center of gravity and roll center). Where mixed traffic at different speeds is
operated, you inevitably have compromises. In the case of the N&W in the
mountains, the coal trains would tend to slip down against the lower rail,
increasing rail and flange wear as well as train resistance. Also, a long, heavy
train stretched around a sharp, superelevated curve has more of a tendency
to "stringline", increasing the possibility of derailments.

So, once the passenger trains were gone, it made sense to lower the
superelevation to a value more consistent with the typical coal train speeds.

Dave Phelps

In a message dated 6/29/2006 11:26:22 P.M. Eastern Daylight Time,
nw-mailing-list at writes:

What might not be related is what was told me regarding the famous 13-degree
curve at Cedar, WV, by Bob Saxtan. It is that the superelevation of this
curve was lowered and the curve was tightened after the end of N&W passenger
service- what would be the reason for these modifications?
I might note something that happened on the night of January 23, 1956. The
611, running the Pocahontas westbound, wrecked there at 12:51 AM. During the
wreck, the 611 tipped over on the curve, and seemingly "jumped" over the
inside westbound rail of the curve, then grabbed one of the rails of the eastbound
track, which she pulled with her on her way onto the bank. I might ask if
any of you want to comment on how the 611 made this "jump" as she did, even
with the little room (as I have seen) between the curve tracks and the bank as I
have seen at Cedar.
Lois J. Ponton
Author of 611 wreck book "Midnight on the Pocahontas"


From: nw-mailing-list at
Reply-To: NW Mailing List <nw-mailing-list at>
To: NW Mailing List <nw-mailing-list at>
Subject: Re: steam loco question
Date: Tue, 27 Jun 2006 22:31:35 -0700 (PDT)

How was all of this effected by superelevation of the track?
I have never totally understood why they used it but it sounds like it would
enhance the effect of the conical wheels.
Jim Hall

nw-mailing-list at wrote:

I won't repeat the answers given so far, which are all correct and well
explained, but there's two more factors, as it's been explained to me over the
years (I'm an old electron pusher, so I take these things on faith): were not
most steam locomotives built with a certain amount of lateral motion allowed
the journal boxes? Even thought the frame and bearings would hold the
driving axles parallel, the ability to shift laterally slightly would also help.
Secondly, while in the ideal case the conicity of the wheel sets would
eliminate or minimize flange contact, in the real world there is flange contact.
As long as the angle of attack of the flange is small and the shape of the
flange is correct, the wheel will not climb, but rather the flange will keep
the wheel in place. The geometry of the flange and rail head result in a
measure called the "L/V" ratio, the ratio of the lateral force (which tends to
cause flange climb) to the vertical force (which keeps the wheel in place). I
have read what a desired limit of the L/V ratio is but I confess I didn't
commit it to memory.

Dave Phelps

In a message dated
6/27/2006 9:16:08 P.M. Eastern

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