Superliner Stability

[SD70Dude]

Lithonia Operator

What is CEM?

Collision/Crash Energy Management

[Lithonia Operator]

What is CEM?

[PJS1]

Overmod,

I understand top heavy vehicles are more prone to roll over in a crash. 

 

The purpose of my question(s) was to gain some insights into what controls, if any, the designers of the Superliners baked into the cars to reduce the probability of rollovers or, if they happen, the controls designed to mitigate the impact.

 

Your insights, which appear to be based on sound engineering principles, are very helpful.  I appreciate them.  

[charlie hebdo]

Overmod

charlie hebdo will agitate for better CEM in the passenger areas,

Jargon, Jargon.  And purple prose. 

[Overmod]

Oh, for heaven's sake, of course they are more prone to roll over in a derailment, and equally of course to do so very quickly if they derail sufficiently to put wheels over the edge of the ballast prism.

If you look at the overturning moment arm at the bolster, and compare it with the roll center, you can easily see the instability just for slight lateral tilt, let alone accelerated roll.  To me the problem is exacerbated by the design of the Waggon Union low-unsprung-mass trucks, but both they and the GSC trucks just don't have serious roll control for more than small perturbations.

I have not studied the extent to which Superliners 'going over' will torque the coupling to accelerate tipover.  It shouldn't be difficult to calculate.  I thought years ago that 'high-level' cars ought to have rotary couplers to prevent that sort of cause of accelerated overturning.

There really isn't much that can be done to make the situation 'safer'.  As with the generations of lightweight car that went before, something can be done about the windows breaking out and projecting people far enough to be dragged or 'rolled over on'.  The issue then becomes what happens if those windows then have to be removed or 'opened' to get people out...

You could have some kind of 'landing gear' that projects out to slow down the roll.  Or large air bags that deploy sequentially to help hold the car upright or at least cushion the rollover.  The reason these are Not Particularly Good Ideas is that all sorts of fun ensues if they deploy unintentionally.

You might get somewhere by adopting the Pendulum Car style of 'tower' up to the floor of the upper level, which essentially 'hangs' all the lower floor structure to generate restoring force, or the Cripe-style pendulum suspension from the roof (with the portal in the frame moving relatively slightly on the upper level, where that most matters) -- reinforcing the car structure accordingly.  If you combined this with the sort of exaggerated OSH construction in the last orders of New Haven cars, you'd get maximum effective bolster plank width; and you could fire a pyrotechnic charge and foam into the air bags on the car to give some active force early in a tipover, although again I think the cure would be worse than the disease.

charlie hebdo will agitate for better CEM in the passenger areas, and I'll pre-emptively agree with him that that's the best, most easily implemented, and perhaps overall the most effective method of preventing injuries when, not if, the things tip over.

[BEAUSABRE]

I'm sure there is AAR, FRA or both standards on CG and propensity to rolle CFR :: 49 CFR Part 238 -- Passenger Equipment Safety Standards

[Enzoamps]

I don't know, but it would seem the important thing is center of gravity rather than how tall they are.  And I don't know that about either.

[PJS1]

What is the likelihood of Superliner cars rolling over in a derailment compared to single level cars? 

 

Do the Superliner cars have any features that reduce the probability of a rollover?