How fast does a train have to go to derail itself on a turn?

Question

How fast does a train have to go to derail itself on a turn?

Answer 1

There is no unsafe speed for a train provided that conditions are right.  Some trains have gone 300 MPH and had no problems.  Amtrak's Acela Express runs 150 MPH on a daily basis.

Answer 2

It depends on the angle of the curve or turn.It cant be mentioned!(according to my view)

Answer 3

Above answers are right, think about it this way, if someone asked how fast a car would have to be going to slide off the road  there is no correct answer.

I've derailed at 10 MPH, not by the train turning over but the rail rolling over beneath the train.

There are literally thousands of variables.

Answer 4

There are too many variables to really answer that. It would be affected by track curvature,track elevation and condition,train tonnage,even excess lateral in the locomotive trucks.The train gods play a big part in your luck too.I have seen trains go around a 40 mph curve at 70 and make it! Mind you I wasn't at the controls at the time but i did get to go along for the ride.I wouldn't have wanted to try it at 72 mph. I do know that much! The pucker factor was good enough at 70.We bounced our way around the corner with our breath held.When we released that breath it was to rip a chunk out of the azz of the boy running it.

Answer 5

"LOV" is usually the culprit that causes derailments in curvature.  No misspelling and not that kind of love.  Here "LOV" stands for "Lateral Over Vertical" forces, or, L/V.

It is the ratio between the vertical, or downward force and the lateral, or sideways force, sometimes called centrifugal force, as a train traverses that curve.

As long as the vertical force is greater than the lateral force, the equipment will stay atop the rail.  But, as soon as the "L"ateral forces become .9 of of "V"ertical force, the equipment will climb the rail towards the outside of the curve, "jack-knifing", or be pulled off the track on the inside of a curve, in a phenomenon called "string-lining."

The latter is what caused the infamous derailment at Cantara Loop in 1991, killing every living thing in the Sacramento River for 30 miles.

So, the speed at which a train can negotiate a curve before derailing varies, as Andy points out, depending on the degree of curvature.  There is also luck, and as any hogger will tell ya, I"d rather be lucky than good any day...  but speed isn't the only thing that can generate excessive forces.

Keep in mind, the forces levels in a moving train are not "steady state," but rather are dynamic.  One such example is when slack action runs through the train.  There is a minimum of a foot or two of slack between each car, much more with sliding draft gear.  So, in a 100 car train, the front of the train can move, or stop, 100 feet before the rear end sees any change.

If controlled, these energy "spikes" run through the train normally, and within the parameters of what the roadbed and equipment are designed to handle.  But, if in uncontrolled fashion they run through the train (such as happens in an emergency application of the brakes), if an excessive spike happens within a curve, the equipment momentarily exceeds the L/V ratio and will climb the rail, regardless of speed.

As a matter of fact, and in a perfect example of how speed is sometimes not a factor at all, if you wish, click on my smiling face and go to my profile page.  Once there, access my 360 profile.  Once there, click on View Blog.  Then, at the top of the page click on the little yellow letters that say "List View."  Once there, click on the post of 04-06-08.  You can also get there using the calendar displayed.  There you will see the details where a train derailed, due to L/V, in a curve, just as your question asks, while the train was STANDING STILL!!  It is an interesting read...