Western Railroad Discussion > Tehachapi derail pictures from Broome Rd

Trying out my 500 MM lens

Not sure what kind of vehicle is in the car,,looks like trucks.

Ct97

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In the first photo, at least for the modelers amoung us, I believe we have found a prototype for the Intermountain Autorack side panels.

Jay

Nice work in getting those aftermath shots!

I wonder if loaded autoracks tend to derail more easily than other freight cars due to the likely possibility they may have a high center of gravity. Some derailments occur at slow speed in tight curves particularly in freight trains with high centers of gravity.

One person explains it this way: "The main reason for this phenomenon is unloading in the outer wheel, which goes to a critical situation because of the larger superelevation that creates an inward acceleration, resulting in an unloading. Because of the action of outer wheel as the steering force, this can lead to the climbing of wheel according to the Nadal formula, which expresses the relation between the lateral forces on the wheel and the vertical downforce of the wheel on the rail."

Another person explains the Nadal fomula: "The Nadal formula is an equation in railway design that relates the downward force exerted by a train's wheels upon the rail, with the lateral force of the wheel's flange against the face of the rail. This relationship is significant in railway design, as a wheel-climb derailment may occur if the lateral and vertical forces are not properly considered.....Typically, the axle load for a railway vehicle should be such that the lateral forces of the wheel against the rail should not exceed 50% of the vertical down-force of the vehicle on the rail. Put another way, there should be twice as much downward force holding the wheel to the rail, as there is lateral force which will tend to cause the wheel to climb in turns. This ratio is accomplished by matching the wheelset with the appropriate rail profile to achieve the lateral force/vertical force ratio desired. If the lateral force/vertical force ratio gets too high, the wheel flange will be pressing against the rail face, and during a turn this will cause the wheel to climb the face of the rail, potentially derailing the railcar."

Then we could go into the Wagner formula, which also takes into account the hunting oscillation of the wheelset and the movement of the wheel flange contact point against the rail, which the Nadal formula does not. I'll let those curious about this explore the subject further on their own.

With such a small collision impact of the lead engine this might add some light as to why there was such a large derailment at low speed in this incident. My thoughts about it anyway.

Fred Harrison
Central Point, OR
CORPpower/JSS/EORS

garr Wrote:
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> In the first photo, at least for the modelers
> amoung us, I believe we have found a prototype for
> the Intermountain Autorack side panels.
>
> Jay


LOL! That was hilarious!