Re: (erielack) Portage Viaduct speed limits

["Paul Brezicki" <doctorpb_@_bellsouth.net>]

Your friend's comment on the 15mph speed limit is not quite correct. Let me 
give some background on the covered hopper incident. The 1960's saw 
increasing numbers of longer, heavier freight cars, including 50-54' covered 
hoppers. At the same time, track conditions on much of the rail network in 
the Northeast and Midwest began to deteriorate due to deferred maintenance. 
Poorly maintained jointed rail tends to get battered down at the rail 
joints, a tendency exacerbated by heavier cars. This is apparent in many 
photos taken on EL and others, particularly wedge shots taken with a 
telephoto lens. The wheelbase of 50-54' cars is close to the 39' joint 
spacing of stick rail. If the joints on the left- and right-hand rails 
happen to be evenly staggered, it tends to produce a rocking motion as the 
car travels over the track, and both trucks hit the low joints at the same 
time on one side, then the other. This is further exacerbated by the 
relatively high center of gravity of loaded CH's, and due to motion 
harmonics of the cars and truck springs, is most pronounced at 15-24 mph. 
This caused many so-called "rock-off" derailments. For this reason, 
engineers of trains with this type of equipment were advised to accelerate 
and decelerate as quickly as possible through this speed range, ie spend as 
little time there as possible.

Getting back to the EL example, the 40' wheelbase of the 20000-series 
cylindrical CH's was very close to the 39' length of stick rail sections. 
After one such car rocked off the bridge, the following was added to TT 
special instruction 1901, which deals with observation of trains: "If 
rocking action of cars becomes excessive, stop must be made and train 
restarted." Also, "If for any reason a freight train cannot maintain speed 
above 24mph, immediate action must be taken to reduce speed to not exceeding 
15mph." (I'm quoting DeYoung's caption here.) So the 15mph speed limit 
applied only to trains that contained 50-54' CH's. Admittedly, this would 
apply to most trains on the Buffalo division, and since 25-30 mph is such a 
small window, it's possible that they just set it to 15mph for these trains. 
Perhaps someone with a post-1964 ETT can advise.

Paul B

From: "Schuyler Larrabee" <schuyler.larrabee_@_verizon.net>
Subject: (erielack) Portage Viaduct speed limits

Quoting a knowledgeable friend:

"It was 15 [mph] in the 60's when the cylindrical covered hopper rock itself 
into the gorge. I am
not sure when it went to ten, but it probably was the 80's. I'd have to go 
through a bunch of
timetables that I don't have to find out, and I'm not THAT interested. 
Industry rumor has it that NS
is going to derate it to 263,000 lb. per car from the current 273 because 
they cannot put a speed
restriction of less than ten on a bridge."
 


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