• Empire Builder on the Ground in MT

  • Discussion related to Amtrak also known as the National Railroad Passenger Corp.
Discussion related to Amtrak also known as the National Railroad Passenger Corp.

Moderators: GirlOnTheTrain, mtuandrew, Tadman

  by photobug56
 
TurningOfTheWheel wrote: Sun Oct 03, 2021 12:12 am
photobug56 wrote: Fri Oct 01, 2021 11:46 pm What is truck hunting, and what can cause it?
The Wiki article on hunting oscillation has a useful animation to see what's going on. I can't explain the phenomenon very well, but as I understand it, at high enough speeds, slippage can occur and the two wheels on each axle can start spinning at different speeds. When this happens, there is an oscillation induced in the vertical axis—from a bird's-eye view, the axle will appear to turn back and forth. It's called a "hunting oscillation" because the wheels are "hunting" for some equilibrium where they are either both spinning at the same rate or agree on the direction they should be headed given the difference in their rotational speeds.

https://en.wikipedia.org/wiki/Hunting_oscillation
I've read of 'modern' trucks / wheel sets where each axle can 'steer' separately from the other. Though I don't know if it's heavily used. And from what I've seen and what you are saying, the wheels on a given axle are solidly attached to the axle so that the 2 wheels and axle normally spin as one. I'm wondering if that's just to save money or if there is another reason.
  by R Paul Carey
 
By way of explanation, wheels are pressed on the axles and therefore two wheels on the same axle will turn at the same speed.

The tread area of the wheels (the portion making contact with the rail) is conical - not cylindrical - in its profile. In effect, the tread diameter is greater in proximity to the flange, tapering from the edge of the rim. This is to minimize rolling resistance and wear in negotiating curvature.

Curve geometry is designed to maintain a prescribed degree of "underbalance" or "cant deficiency" at the designated maximum speed, which - by design - causes the wheel set to "track" against the outside or high rail in a curve.

Think about it this way: the wheel following the outside rail in a curve has farther to travel than its mate on the low rail. The conical profiles make up the difference as the wheel set follows the outside rail in a properly maintained curve.

As to this particular derailment, I would be particularly interested to see if the investigating parties are able to rule out buckled track ("sun kink") as the probable cause, based upon the appearance of shifted track in advance of the switch.
  by STrRedWolf
 
R Paul Carey wrote: Sun Oct 03, 2021 7:40 am As to this particular derailment, I would be particularly interested to see if the investigating parties are able to rule out buckled track ("sun kink") as the probable cause, based upon the appearance of shifted track in advance of the switch.
Given previous statements by the NTSB about where the accident started, plus statements made by former NTSB investigators to NBC News and other news outlets, a sun kink located at the curve before the switch may be the case. Remember, 7/27 goes westbound and the switch in question is the east-most switch for that siding. Three cars flipped well before the switch.
  by BandA
 
Doesn't BNSF pre-stress their continuously-welded rail to prevent buckling?
  by justalurker66
 
BandA wrote: Sun Oct 03, 2021 11:48 amDoesn't BNSF pre-stress their continuously-welded rail to prevent buckling?
Sure. But air temperature went from 43° overnight to 91° on the day of the derailment (Havre, MT). Not quite as bad as the 28° to 92° swing one week prior. (Track temperature unknown.) Metal contracts in the cold and expands in the heat. The rail temperature at the time each join is welded is taken into account. The temperature in Havre is usually between 9° and 87° over the course of the year.
Havre092021.png
The NTSB stated that they were looking at the video from head end cameras on the Amtrak train as well as the freight that passed 80 minutes earlier. They may provide decent information.
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  by photobug56
 
Adding cameras to loco cabs plus black boxes may help a lot with crash investigations and in learning more on how to prevent them. Hopefully the case here.
  by Gilbert B Norman
 
Gentlemen; PAYSHANCE!!

This is not an aircraft that crashed at sea. Everything is there on the ground and was secured in short order.

The NTSB is the best crash investigative outfit in the business; they will determine the cause.

Let's give 'em time.
  by MACTRAXX
 
GBN: I will second your thoughts - Give the NTSB investigation time to find the cause of this derailment.
Some of the "rushing to judgement" that we see these days can be a product of the 24 hour media news cycle.
The NTSB will eventually issue a detailed report of the wreck with co-operation of the FRA, Amtrak and BNSF.
MACTRAXX
  by charlesriverbranch
 
OK, I'll bite: what railroad anywhere in the world requires passengers to wear seat belts?
  by Gilbert B Norman
 
Well, by that same token, Mr. Charles, where until RSIA 08 was any railroad required to have any system of Positive Train Control without regard to train speed or Class of Service?

Hey, my auto, as well as those of many others around here, has it. Some could say what took the roads so long? Why wasn't "hey, we're paying some guy $125K a year to be our PTC.

Well, Chatsworth, DuPont, Frankford Jct, Goodwell, Panhandle, kind of set that notion aside.
  by eolesen
 
When school, city and intercity busses have seat belts, we can discuss them on trains....

Well aware that some districts do indeed have seat belts added to their busses, but they are by far the minority nationwide, and compliance is horrible from what I'm told.



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  by photobug56
 
School buses and intercity buses should have them. City buses tend to have tiny seats, bench seating where seat belts (except for express busses) tend to be impractical. Intercity trains could probably do seat belts (lap) fairly easily, ignoring the expense.
  by BandA
 
There was a school bus rollover accident in maritime Canada (from the US) where there were fatalities that would have been prevented if the students were belted. That city now requires seatbelts on their school buses. (Driver who was unfamiliar with the route, who didn't speak English, multi-hour trip and was driving much too fast on an off ramp.)

I have read that three-point seatbelts would require stiffer seats that would cause more injuries in unbelted passengers. This doesn't seem to make sense to me but I am not an expert.
  by ExCon90
 
photobug56 wrote: Mon Oct 04, 2021 1:53 pm School buses and intercity buses should have them. City buses tend to have tiny seats, bench seating where seat belts (except for express busses) tend to be impractical. Intercity trains could probably do seat belts (lap) fairly easily, ignoring the expense.
It's worth noting that in retrofitting existing vehicles the seatbelts have to be anchored to the vehicle frame, not the seats. Sounds expensive, and I would think the same would be true on existing rail cars.
  by photobug56
 
BandA wrote: Mon Oct 04, 2021 5:37 pm There was a school bus rollover accident in maritime Canada (from the US) where there were fatalities that would have been prevented if the students were belted. That city now requires seatbelts on their school buses. (Driver who was unfamiliar with the route, who didn't speak English, multi-hour trip and was driving much too fast on an off ramp.)

I have read that three-point seatbelts would require stiffer seats that would cause more injuries in unbelted passengers. This doesn't seem to make sense to me but I am not an expert.
School bus seats are stiff to begin with.
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