Kinky, man

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Posted by tree68 on Thursday, January 04, 2018 11:13 AM

VOLKER LANDWEHR

In 1944 the Army tried to derail a train by blowing out pieces of rail. The results are surprising: https://www.youtube.com/watch?v=agznZBiK_Bs
Regards, Volker

That's the one.

LarryWhistling
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Posted by Overmod on Thursday, January 04, 2018 10:28 PM

tree68
VOLKER LANDWEHR

In 1944 the Army tried to derail a train by blowing out pieces of rail. The results are surprising: https://www.youtube.com/watch?v=agznZBiK_Bs
Regards, Volker

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Posted by Paul_D_North_Jr on Friday, January 05, 2018 2:54 PM

blue streak 1
PDN  Would your micrometer have to be at the same temperature for both measurements ? Or can it be calibrated before each measurement ?

About pull aparts.  If a train runs over a pull apart or at least part of a train how much damage will happen to the wheels for various distances ?  That of course would depend on how much distance the pull apart is.  Certainly more than a low rail joint.  Wheel rail confence question ?

The micrometer should be at the same temeprature as you suggest, and the actual measurments then adjusted to a standard reference temperature.  But that's a minor source of error, and wouldn't affect the conclusion, which is that the transverse change in dimension due to Poisson's Ratio is trivial/ insignificant for most practical purposes. 

As the effect on wheels - that's best answered by a Mechancal Dept. person.  I can say that the FRA allows railroads to authorize signalmen and MOW personnel field personnel to permit very slow speed (5 - 10 MPH as I recall) moves of trains over pull-aparts so as to keep the line moving, pending a repair.  Presumably they wouldn't do that if there was a risk of wheel damage. 

An opposite case was reported in the AREMA Proceedings a couple years ago.  Something left gouges in a light rail system's new rail for about 2,000 ft. as I recall.  It took quite a bit of detective work to figure out that it was apparently caused by a very hard machining tool bit that somehow became stuck in a light rail vehicle's wheel, though that is speculation because it was never found. 

- PDN.  

"This Fascinating Railroad Business" (title of 1943 book by Robert Selph Henry of the AAR)
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Posted by Murphy Siding on Wednesday, January 10, 2018 12:30 PM

How wide can a pull-apart be and still allow the train to go over it?

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Posted by Semper Vaporo on Wednesday, January 10, 2018 1:03 PM

As long as the wheels remain aligned with the other end of the gap and there is sufficient energy to climb the infinite grade of the broken rail end, it could be miles and miles.  In practical terms, due to the variation in what is in the way along the bumpy ride over the ties and ballast, probably not very far.  Watch that video referred to above and you will see that the gap can be substantial.

Semper Vaporo

Pkgs.

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Posted by Overmod on Wednesday, January 10, 2018 1:31 PM

Murphy Siding
How wide can a pull-apart be and still allow the train to go over it?

Also depends very substantially on whether it's in a curve, if there is strong crosswind or other force tending to push a flange outward, or if the car is behind a DPU node in substantial buff (when small incremental changes in lateral force no longer self-correct as they do in draft). 

I would suspect constant-contact side bearings are your friend in keeping truck yaw minimized over what is basically the analogue of a severe staggered low joint, even in some curves.

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Posted by Paul_D_North_Jr on Wednesday, January 10, 2018 2:24 PM

Semper Vaporo
 . . . and there is sufficient energy to climb the infinite grade of the broken rail end, . . . 

Roughly 4.5 to 5 MPH [for those who want to know, by h = v^2 x 2G  where h = 8" = 0.67', solving for v in ft./sec., and then converting to MPH].  

- PDN. 

"This Fascinating Railroad Business" (title of 1943 book by Robert Selph Henry of the AAR)
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Posted by Semper Vaporo on Wednesday, January 10, 2018 3:03 PM

Paul_D_North_Jr
Semper Vaporo
 . . . and there is sufficient energy to climb the infinite grade of the broken rail end, . . . 

Roughly 4.5 to 5 MPH [for those who want to know, by h = v^2 x 2G  where h = 8" = 0.67', solving for v in ft./sec., and then converting to MPH].  

- PDN. 

Offhand, I would think that diameter of the wheel and weight of the car should be a part of the calculation.  Given the energy to pull, I think it should be possible to lift the empty or loaded car the required distance above the rail at a speed of fractions of a furlong per fortnight... assuming the wheel diameter would put the center of rotation above the height of the rail, otherwise the pull would just be trying to squish the end of the rail.

 

Semper Vaporo

Pkgs.

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Posted by erikem on Wednesday, January 10, 2018 9:44 PM

Semper Vaporo

Offhand, I would think that diameter of the wheel and weight of the car should be a part of the calculation.

Unless we're talking about very small diameter wheels with the gap greater than the wheel diameter, the wheel is going to bridge the ends of the rails. For a 4 inch gap with wheel with a 36 inch tread diameter, the wheel will only drop about 0.1". For an 8 inch gap, the wheel will only drop ~0.45".

Offhand, I'd say you were on the right track.

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