The last three auto rack trains that I saw near Temple had a distinct banging coming from the last two or three cars. It appeared to isolated on in these cars. What might it be?
Was it rythmic (flat spots), or random (possibly slack)?
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
tree68 Was it rythmic (flat spots), or random (possibly slack)?
I don't believe it was flat spots; it sounded like a banging inside the car, which could be caused by slack action.
Two of the trains were coming out of the fueling station just south of Temple; one of them was arriving.
I've heard that on the Deshler cam, when racks are on the transfers (wyes). You'll also sometimes get banging if the track is uneven (it doesn't take much) as the coupler faces adjust.
Auto racks are one of the ones that I see doing this the most:
As the tail end of the train nears there is less stress on the drawbars.
Often one drawbar will be slightly higher than the other and there will be a bang as the higher one drops down in line with the lower one as the train goes over a little bump or dip in the tracks.
10000 feet and no dynamics? Today is going to be a good day ...
traisessive1 Auto racks are one of the ones that I see doing this the most: As the tail end of the train nears there is less stress on the drawbars. Often one drawbar will be slightly higher than the other and there will be a bang as the higher one drops down in line with the lower one as the train goes over a little bump or dip in the tracks.
Correct-a-mundo! It could also happen in front of a DPU that's doing its job properly.I happened to be in a position yesterday and today to see this happen often (a grade crossing is a good place for small changes in track level). Slack will also be more apt to run in and out at the tail end of a train, just because forces are so much less. Visual lesson...try to pull a string across the floor at a steady speed, and watch the end of the string hold back, then hurry to catch up. Same thing's going on there.Having said all that, the neatest thing I saw today was an auto-rack train picking up speed from a dead stop, and the slack-banging did not happen (I was waiting for it!)!
Carl
Railroader Emeritus (practiced railroading for 46 years--and in 2010 I finally got it right!)
CAACSCOCOM--I don't want to behave improperly, so I just won't behave at all. (SM)
In rare cases a high/low situation can result in a train separation, as one drawbar lifts right up out of the other.
Tightlock or shelf couplers can prevent this, but can also make coupling difficult in a high/low situation. One industry I used to switch would always leave their loads on flat track right at the top of a steep hill, and the combination of the incline angle and the empty car sitting higher on its springs often meant that making a joint was impossible.
I would try to reach in with a car that had normal couplers, but sometimes we had to resort to lifting the low drawbar and sticking a rock underneath it to prop it up. It was quite satisfying to see the rock disintegrate as the joint finally made.
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