"Albia Police Chief Jay Andrews says the derailment could have been caused by the railroad tracks slightly separating."
http://gazetteonline.com/local-news/statewide-news/2010/07/30/tracks-cited-as-possible-factor-in-southern-iowa-train-crash
Assuming Chief Andrews means rails moving too far apart from the prescribed gauge, what would cause this? Would recent heavy rains be a factor?
Not sure of the exact cause, but last week there was a minor derailment on the B&P line, where a single wheel fell between the tracks, seemingly due to bad ties not holding the rails together. That derailment was on Friday, July 23, the PSSR, unknown location, one railcar, the S wheel, of the N truck, on the E side of the train fell in.
Just as likely there was a broken rail, perhaps with a piece missing instead of a simple fracture. In winter a fracture often causes the rails to pull apart, but in summer a gap will usually tend to close up. With a broken rail, though, a lot depends on how well the spikes are holding and if the rail is properly stressed and anchored. Track geometry, especially if the rail is on the outside of a curve, can also play a role.
John
Victrola1 [snip] Assuming Chief Andrews means rails moving too far apart from the prescribed gauge, what would cause this? Would recent heavy rains be a factor?
Bad tie condition = rotten wood ties is the most common cause . Either they can't hold the spikes that keep the rails to gauge in place well enough to keep them from moving horizontally outward, and/ or the spikes are so loose that when the tie 'pumps' = moves up and down under a train, the spikes gradually work their way out of the tie. Sometime along in that process the spikes cease to provide adequate restraint for the rails, and the gauge widens . . . If the ties are concrete and/ or some other kind of steel-based rail-tie fastener is being used, then it's likely something just flat-out broke loose. With those materials, rot/ deterioration is usually not a factor, though sometimes concrete ties will degrade/ abrade/ wear under the rail seat enough to again allow too much rail movement, and hence wide gauge.
Heavy rain by itself will not cause wide gauge over a short time span - ties don't rot that quickly, and the rail-tie fastening systems are otherwise pretty much immune to rain/ moisture. However, if the subgrade was really weakened such that the track deflection/ motion under load became extreme - like more than an inch or two - then again it's possible that ties would come loose and remain stuck down in the mud, and so the rails would be loose and could flex wider under train loads. And/ or, the track could be out of cross-level and warped so much in the mud that the railcar wheels push out on 1 rail a lot harder, and either climb over that rail sideways, or the rail drops down from the wheels faster than they can follow and the car literally 'runs off the track', which is more likely in sharper curves. Theoretically the 'H-shaped bolster and truck sideframes suspension for the railcar wheels is flexible enough that they can stay in constant contact with the rail - but at the extremes, that doesn't always hold true . . .
- Paul North.
Victrola1 http://gazetteonline.com/local-news/statewide-news/2010/07/30/tracks-cited-as-possible-factor-in-southern-iowa-train-crash
Why this made the local paper in the north end of the state I have no idea.
RRKenVictrola1 http://gazetteonline.com/local-news/statewide-news/2010/07/30/tracks-cited-as-possible-factor-in-southern-iowa-train-crash Why this made the local paper in the north end of the state I have no idea.
Gazetteonline is the website for the Cedar Rapids Gazette, Ken. We're east-central.
Brian (IA) http://blhanel.rrpicturearchives.net.
Paul_D_North_Jr Victrola1 [snip] Assuming Chief Andrews means rails moving too far apart from the prescribed gauge, what would cause this? Would recent heavy rains be a factor? Bad tie condition = rotten wood ties is the most common cause . Either they can't hold the spikes that keep the rails to gauge in place well enough to keep them from moving horizontally outward, and/ or the spikes are so loose that when the tie 'pumps' = moves up and down under a train, the spikes gradually work their way out of the tie. Sometime along in that process the spikes cease to provide adequate restraint for the rails, and the gauge widens . . . If the ties are concrete and/ or some other kind of steel-based rail-tie fastener is being used, then it's likely something just flat-out broke loose. With those materials, rot/ deterioration is usually not a factor, though sometimes concrete ties will degrade/ abrade/ wear under the rail seat enough to again allow too much rail movement, and hence wide gauge. Heavy rain by itself will not cause wide gauge over a short time span - ties don't rot that quickly, and the rail-tie fastening systems are otherwise pretty much immune to rain/ moisture. However, if the subgrade was really weakened such that the track deflection/ motion under load became extreme - like more than an inch or two - then again it's possible that ties would come loose and remain stuck down in the mud, and so the rails would be loose and could flex wider under train loads. And/ or, the track could be out of cross-level and warped so much in the mud that the railcar wheels push out on 1 rail a lot harder, and either climb over that rail sideways, or the rail drops down from the wheels faster than they can follow and the car literally 'runs off the track', which is more likely in sharper curves. Theoretically the 'H-shaped bolster and truck sideframes suspension for the railcar wheels is flexible enough that they can stay in constant contact with the rail - but at the extremes, that doesn't always hold true . . . - Paul North.
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