Mudchicken, in the UK crash investgators are looking at loose bolts in the switch as a possible cause of Friday’s passenger train derailment. If true this would be the same problem as caused the more serious derailment and collision at Potter’s Bar a few years ago. Are US switches constructed similarly to those in the UK, with slack adjustment using threaded rodding and nuts?
(earlier answer got lost in a server burp, never to be seen again?)
If it’s the basket rod (alias #1 rod) attached to a switch machine, not much difference between here and Great Britain.
If it’s bolts in the heel block at the heel of the switch points (hinge point), then it might be different. Use of solid cast blocks at the heel of switch is rare anymore in this country, except in yards and backtracks. New turnouts come with hook -plates that do away with the use of bolted heel blocks, although the hook plate can accomodate old style switch points with angle bars (angle bars not to be adjusted)…
England is playing catch-up with American railway practices. Britain uses more people and less machinery. Like the news media in most places, reporters tend to get lost in details.
****From the description lifted off the othere thread:
(1) Derailment happened at a manual hand-thrown electric locked switch
(2) The small bolt that holds one of the #1 rod (switch stand to switch points) connections to a transit clip (slang: elephant ears, connects rod to machined/milled switch point) on a switch point failed.(In the US, those small bolts have a cotter pin through them to stop the nut from unthreading) If that bolt comes out and there is no secondary #3, 4, 5 rod and transit clip set, that switch point is free to move and slide around on the switch plate. If that switch was in a curve (a no-no in this country, but they still are around and every track designer/roadmaster’s nightmare, then all bets are off)
Further information regarding the derailment:
Investigators at the scene of a fatal high-speed rail crash in northwestern England discovered that parts were missing from a set of points where the train derailed, the Rail Accident Investigations Branch said Monday.
…
In their report Monday, investigators said that solid bars which hold the points in position were missing.
“The left hand switch rail was free to move across close to the left hand stock rail whilst the right hand switch rail remained, correctly, against the right hand stock rail,” the report said.
“The train wheels were thus set on a course where the gauge was narrowing as the train moved forward. The train wheels, (which are rigidly mounted on an axle a fixed distance apart), could not follow the narrowing route and climbed over both switch rails, and then ran in a derailed state,” the report added.
From here
http://news.bbc.co.uk/1/shared/bsp/hi/pdfs/26_02_07_grayrigg.pdf There is a download of the interim accident report here - - and a good diagram in this news item - http://news.bbc.co.uk/1/hi/uk/6398057.stm
All four stretcher bars between the switch blades were missing, fractured or unbolted.
The big question is how the switch got into that state when it was apparently inspected and passed as fit for use only a few weeks before ?
Tony
Either terribly stupid/criminal negligence maintenance or criminal activity. Something does not add up.
If the “spacer bars” (#1, #3,#4, #5 Rods - numbered for whatever crib between the ties they sit in, going away from the tip of the switch points) were left out for ANY reason, the switch point against the bent stock rail is clamped shut and the other switch point is removed or fixed in the open position until the switch can be made whole again. In the US, most railroads annually magnaflux or otherwise inspect for microcracks the #1 rod/ basket rod looking for failures in main track switches. The design of the connecting rods is such that you do not have to remove all the other rods to replace the defective rod. Being main track, these spacer bars would also have to be insulated which could bring up a really dumb scenario like a signal maintainer trying to eliminate a track light removing switch rods looking for the cause [bad insulation in a connecting rod] of an unwanted electrical shunt in a track circuit in the absense of a track gang.
Sad, whatever the story is.
My thoughts too - it’s awfully reminiscent of the accident at Potters Bar (near London) in 2002 caused by a badly maintained - or intentionally damaged - facing switch.
Tony
I’ve been trying to make sense of it, too. From the RAIB interim report, it seems possible that one of the spreaders may have been intact (although quite possibly fractured) when the engine hit it – although it would appear that the others were either broken or just plain not screwed together. Which is nearly incredible. I am much more inclined to the ‘terribly stupid’ side, though, sad as it may seem. It is quite hasty to draw conclusions, but it would appear that whoever was supposed to look at the switch (assuming that, in fact, he or she did – which is in question) either didn’t know what to look for, or didn’t appreciate what he or she saw. Training issue, perhaps. It will be interesting (?!) to read the full report; RAIB is pretty quick, all things considered, with those things. If it should turn out to be a faulty inspection problem, it won’t be the first on Network Rail, as a casual scan of the past RAIB reports will show.
A few weeks is a LONG time to go between track inspections. On a U.S. track with trains travelling 90mph (Class 6) it would be inspected twice weekly. Operation of the switch must be inspected and tested at least monthly. 49 CFR 213.
8NS
As far as I know, general track inspections do take place at least weekly - a ‘few weeks’ was the time since the last detailed examination of the switch (according to the reports/comments I’ve seen since the accident).
Tony