Fall (almost), the weather cools down, we can open the windows, and hear the trains at the crossing about 8 blocks from my front door.
Last night, as I was sitting on my front porch swing listening to a train(sounds like a country song!). There was an empty grainer or ethanol train headed south. I could hear the shimmy-shimmy sound. A couple of day ago, I was waiting at that crossing as an empty ethanol train rolled by. Every now and then, a batch of cars would start to shimmy and vibrate. This sound would radiate forward and backward a few cars from where it started. Then after 5 or 10 seconds, the sound would stop. There was no rhyme or reason as to where or when it started. The sound was what I imagine a 100 ton slinky would sound like cartwheeling down some really big steps.
Any ideas about what may cause the shimmy-shimmy sound?
Might it be some function of track alignment, or a settling of the road bed?
Years back there was a serious problem with jointed rails and the"then new" cylindrical aluminum hopper cars, that would rock and roll right off the tracks at train speeds of around (or less than) 30 mph (?).
I thought about that, but there is none of the clanking and banging that usually accompanies slack action. This phenomenon seems to be limited to just a handful of cars. Would the fact the the route is on a barely perceptible incline, and has a slight curve be of any consequence?
Sam- trains i question are either empty steel grain hopper or empty steel ethanol tank cars. The rock trains don’t make the sound, but they’re loaded with rock when they go through this section of track.
The center bowl of a truck bolster fits into a center plate on the body bolster, the liner is a anti-friction material that keeps this high pressure joint lubricated, allowing the truck to turn under the car… It can be made from a nylon material or compressed graphite.
I’ve heard this sound from empty tank cars being switched in the local yard. Seems to be a harmonic vibration that happens when the cars are being pulled hard. Sometimes you can even see them shake ever so slightly.
We recently had a visit from the rail grinder. I’ve noticed where it’s been you can hear the wheels “sing.” I don’t notice it so much with the cab windows closed, but a couple of times this last week I’ve left them open while running and could really hear it. When I first heard it, I wondered what was up. Then I remembered seeing the grinder tied up (and also hearing the MOW pilot assigned to it on the radio) at various places the last couple of trips.
My suspicion about tank cars making that sound is that it’s due to the safety appliances (end handrails and such) being connected in a less-than solid manner in which the railings themselves can vibrate against the stanchions that hold them to the tank or platform. This doesn’t explain why loaded trains don’t seem to sound off as much (to me), though.
They make quite an interesting noise when they come into contact with cars in the bowl tracks, too…
You know, I’ve noticed that too when trains (mostly mixed freights with strings of tank cars mixed in) cross through the center of Troy, AL. The crossing I’m thinking of is practically right on top of two switches and as the tank cars go through the frog area, the tank cars (mostly empties that I’ve noticed doing it), always seem to make a kinda hollow vibrating sound. Haven’t ever noticed the cars themselves shaking pe rse, but I’ve definitely heard the noise.
Empty tank cars are usually open to the air. The open vent acts like the mouth of an stopped organ pipe (Bourdon, Gedakt, Stopped Flute, Stopped Diapason, Quintaton). The air inside acts like the air in a stopped organ pipe. Full tank: Vent closed, very little air inside. The greater the air volume, the lower fundamental frequency of the whhoom. (With a stopped pipe, fundamental is usually much stronger than harmonics, and the octave is missing but the fifth above is present. and so forth with evey other harmonic missing.) Loose stantions are not required to rattle the tank; ordinary vibration from rail joints, the bridge effect of rail deflection not continuously supported but spot supported on ties, etc.
A stopped organ pipe is one with only the mouth open to the atmousphere, with the top covered. Open pipes are Diapasons, Principles, Viola, Dulciana, etc, and have all harmonics.
All of these are flue pipes. There are also reed pipes.
Air is suppled at the foot of the pipe. The “action” controls the air from the bellows and blower to the foot of the pipe, and there are several kinds of “actions.”
I think Jeff called it. I have noticed that ‘singing’ on freshly grounded rail and cars like emty tanks and covered hoppers tend to resonate and amplify that sound more significantly then others.[2c]
The grit size of the grinders is fairly large and does not result in a mirror like surface to the rail. It is more like the pretty pattern on some jewelry that is the result of what is termed an “engine turning”.
This can produce the humming sound as the wheels pass over the rough surface