Many years ago when going back and forth to college pre 911 I would hop a train to the next yard 150 miles away to moms house. I noticed that at a certain speed the boxcar would shake violenty. Grain Cars with a lower center of gravity almost never did this. Could this be due to the vacume effect of the wind shaking the boxcar? I heard that on a Volkswagon they were harder to drive if only one side window was open.
CandOforprogress2 Many years ago when going back and forth to college pre 911 I would hop a train to the next yard 150 miles away to moms house. I noticed that at a certain speed the boxcar would shake violenty. Grain Cars with a lower center of gravity almost never did this. Could this be due to the vacume effect of the wind shaking the boxcar? I heard that on a Volkswagon they were harder to drive if only one side window was open.
Truck hunting is a symptom of wheel and track conditions. Potentially, it can become very violent and even derail the train. Air resistance or windy weather do not produce truck hunting nor the shaking symptoms of truck hunting. But in track/wheel conditions that can induce truck hunting, an empty car is more prone to truck hunting than a loaded car.
I rode quite a few freights back in the day while going to college -- mid-60's on both the NP and GN in Montana, Idaho, and Washington. Back then, box cars with sliding doors were common, and cars with open doors were also common, either one door or both. I prefered both doors open for the scenery, but found absolutly zero difference in the riding qualities in the cars due to doors. I did have one really strange trip tho out of Interbay Yard in Seattle bound for Whitefish, MT.
It was late summer-early fall, and the train was loaded with migrant workers -- now called illegals -- bound for Whenachee, WA to harvest the apple crop. Each empty car had at least 8-10 men in it, which made me uncomfortable since I was in college and had an expensive camera with me. I found an empty box car with no one in it, but I found it strange that one of the doors was laying on the floor, rather than where it should be. Anyway, I got in.
It was about 10PM when we left and I was tired, so I layed down on the floor and wrapped myself in my blanket, mummy style. I had a VERY bad night! You've probably heard of harmonic rocking on grain cars, well this car had a harmonic bounce on the jointed rail. It would be perfectly smooth for a while, then start to bounce. I little at first, but gradually getting worse and worse until I was being lifted off the floor, so much so that I couldn't keep the balnket tucked under me. Then it would slowly settle down to a smooth roll, then start all over again. There probably was a harmonic balance between the rail joints, the length of the car, the speed of the train, and the springing action that went into and out of phase at regular intervals. It was the worst ride I ever had. BHW, everyone bailed at Whenachee and I picked another car -- great ride after that.
Talkin' about the Volkswagen Beetle? It was my first car, and no, no difference in driving with one window open, or both windows open.
One window open, "1-55 Air Conditioning." Two windows open, "2-55 Air Conditioning."
By the way, with only forced-air heating in the Bug if you wanted to stay warm in the winter you had to keep moving! Why they never put a $5 fan in the system I never could figure out.
GN_FanIt was about 10PM when we left and I was tired, so I layed down on the floor and wrapped myself in my blanket, mummy style. I had a VERY bad night! You've probably heard of harmonic rocking on grain cars, well this car had a harmonic bounce on the jointed rail. It would be perfectly smooth for a while, then start to bounce. I little at first, but gradually getting worse and worse until I was being lifted off the floor, so much so that I couldn't keep the balnket tucked under me. Then it would slowly settle down to a smooth roll, then start all over again. There probably was a harmonic balance between the rail joints, the length of the car, the speed of the train, and the springing action that went into and out of phase at regular intervals. It was the worst ride I ever had. BHW, everyone bailed at Whenachee and I picked another car -- great ride after that.
That sounds similar to harmonic rocking, but is a perfect description of truck hunting, especially if you were traveling over 50 mph.
Both conditions have a harmonic nature to them. Harmonic rocking feels like the car will rock so hard and far that it will tip over. Truck hunting feels like the car is oscillating or shaking side to side so hard that a wheel flange will climb the rail high enough to derail the car. Truck hunting has the harmonics of the rapid side to side oscillating. Even if a wheel does not climb over the rail, sometimes the oscillation is violent enough that each side shift will have wheel flanges climbing the rail to the point where the wheel tread lifts off of the rail head. It can also cause the center bearing to lift off of the bowl and then slam back down. These oscillations can occur several times per second.
What you describe particularly sounds like truck hunting in this sense: Truck hunting typically has a second harmonic pattern in which the truck hunting settles down to a perfect ride for maybe 30 seconds. Then it begins a slight oscillation that quickly builds up to the full violence of the maximum oscillation for maybe 30 seconds. It repeats that cycle over and over.
Truck hunting is a nasty condition that can have a car running hundreds or even thousands of miles just on the verge of derailing at high speed and causing a massive pileup. Riding on a car with hunting trucks is physically uncomfortable, but also terrifying.
CandOforprogress2Could this be due to the vacuum effect of the wind shaking the boxcar? I heard that [Volkswagens] were harder to drive if only one side window was open.
This is more interesting than the discussion indicates so far.
An open boxcar door should, indeed, be prone to create the kind of standing vortex oscillation that makes the heavy 'drumming' or buffet in some vehicles with an open window. (Usually this is not severe enough in automobiles to cause more than acoustic discomfort, but it can be pronounced enough to shake glasses out of focus). This would be magnified by a quartering wind which is now trapped in the 'inside angle' of the closed car as well as having impact on the forward corner of the outside as in the kind of resistance we have been discussing for container trains. I can easily see the result of these forces acting in both roll and yaw on the truck bowls, side-bearings and center pins. (The vortex acts with increasing 'lever arm' in roll the higher up in the carbody it makes contact)
How this would 'couple' into hunting of the trucks due to track forces would be an interesting study (hunting is a resonant combination of yaw and roll) further complicated by lateral pressure causing the truck to ride up on the far-side coned treads, perhaps into actual periodic flange contact, and this would be metastable at best with either 'normal' or worn coned tread profiles. The trucks have their own yaw period, associated with wheelbase (or more properly the distance from center pivot to tread) and it might even be possible to have interactions akin to those in a compound pendulum with carbody motion even with longitudinal 'damping' through buff and draft force -- I suspect lateral motion of the car as well as small-degree yaw would be possibly accommodated by the permissible swing in the draft gear tolerated for coupling misalignment as well as some play in knuckle engagement.
Some of the discussion hinges on exactly what "shake violently" means -- is it the up-and-down or harmonic-rock motion, or is it physical yaw of the carbody? Is the 'shaking' more pronounced when, or shortly after, strong wind hits the car?
The boxcar shaking would always wake me up at 200am on the streach of Conrail Lake Erie line outside of Erie PA. The violents shaking would move me and my sleeping bag across the metal floor like electronic football. It would also start and stop for no reason at certain speeds. I assume this could be "Harmonic Rock"? I see what you are saying about the larger open door. Now when I rode grain cars that are loaded with a lower center of gravity this would almost never happen. When they had some hunting it was more like a side to side lulabuy and was tolarble.
CandOforprogress2 The boxcar shaking would always wake me up at 200am on the streach of Conrail Lake Erie line outside of Erie PA. The violents shaking would move me and my sleeping bag across the metal floor like electronic football. It would also start and stop for no reason at certain speeds. I assume this could be "Harmonic Rock"? I see what you are saying about the larger open door. Now when I rode grain cars that are loaded with a lower center of gravity this would almost never happen. When they had some hunting it was more like a side to side lulabuy and was tolarble.
I believe when the facts are shown - a loaded grain covered hopper has a higher center of gravity than does an empty box car. The load of the grain car puts more force on the center plate bowl of the truck and thus acts as a brake against truck hunting.
Never too old to have a happy childhood!
BaltACD CandOforprogress2 The boxcar shaking would always wake me up at 200am on the streach of Conrail Lake Erie line outside of Erie PA. The violents shaking would move me and my sleeping bag across the metal floor like electronic football. It would also start and stop for no reason at certain speeds. I assume this could be "Harmonic Rock"? I see what you are saying about the larger open door. Now when I rode grain cars that are loaded with a lower center of gravity this would almost never happen. When they had some hunting it was more like a side to side lulabuy and was tolarble. I believe when the facts are shown - a loaded grain covered hopper has a higher center of gravity than does an empty box car. The load of the grain car puts more force on the center plate bowl of the truck and thus acts as a brake against truck hunting.
Johnny
CandOforprogress2It would also start and stop for no reason at certain speeds. I assume this could be "Harmonic Rock"?
It is not harmonic rocking. It is truck hunting. Truck hunting has its own harmonics, however, and one of them is starting and stopping for no apparent reason as you descibe in your experience. Truck hunting is a problem with the way the wheels track on the rail head. Normally, the wheel taper is supposed to center the wheels on the rail head when running straight. With truck hunting, the wheels don't center themselves when it is occuring.
Instead, they track sideways back and forth on the rail head, slamming thier flanges against the side of the rail head. Instead of finding the normal equalibrium of straight line tracking, the wheels constantly "hunt" for it as they osclliate side to side.
Truck hunting is caused by worn wheels, but it is also influenced by other factors which can be related to track. But if the truck hunting conditions exist, empty cars are more susceptible to it than loaded cars.
This also happened riding beat up scrap gondolas. I felt like i was a tonka toy being tossed around in a open shoe box
CandOforprogress2 This also happened riding beat up scrap gondolas. I felt like i was a tonka toy being tossed around in a open shoe box
CSSHEGEWISCH CandOforprogress2 This also happened riding beat up scrap gondolas. I felt like i was a tonka toy being tossed around in a open shoe box Perhaps you should consider paying for a bus or train ticket.
Should I report the car # to the yard office?
CandOforprogress2 Should I report the car # to the yard office?
Did that once. Went into Cleveland Collinwood yard office after a rough ride on a cold November night. There was some old Hippy Dispatcher behind the desk. Gave him the car number and I got a hot cup of coffee and a donut for my troubles. I think they pulled the car at Willard at the next yard. That was back when it was still Conrail and Conrail was run by old men from Steam Days and there hippie kids. The dispatch office was a busy station with Jitneys going everywhere and union stickers everywere. Now trying to find a human being in a yard is hard. Went thru New Castle PA in Jan2017. not a soul in the crew room. Just a couple of vending machines.
We have had threads on truck hunting here in the past. Truck hunting is often confused with harmonic rocking because both involve “side-to-side” movement. But the two phenomena are entirely different actions with different causes.
Harmonic rocking is caused by track conditions, and those conditions and their locations are well known by railroad companies, so harmonic rocking is predictable and fixable. Truck hunting is primarily caused by car truck conditions, although track conditions can also add influence.
The truck conditions that cause hunting are worn components interacting in a variety of ways. Routine inspections of trucks might not catch issues that happen to induce truck hunting, so this suggests the need for wayside truck hunting detectors.
I don’t know if such technology is in place today, but here is an earlier proposal on such a wayside detection system:
http://onlinepubs.trb.org/onlinepubs/archive/studies/idea/finalreports/safety/S-06_Final_Report.pdf
Apparently, a linier array of sensors checks the side-to-side position of the wheelsets in relation to the rail alignment. There is an interesting drawing of the wheelset action involved in truck hunting on page 5. Truck hunting does cause derailments, and a table showing the number of such derailments per year is included on page 3.
Here is an excellent video clearly depicting truck hunting:
https://www.youtube.com/watch?v=3i-ViwHubeE
Notice the trucks are twisting on their center bearings as they hunt side to side. This is the actual truck hunting oscillating action. That action then jostles the car bodies side to side.
But notice that the car bodies are not really rocking much as they do with harmonic rocking which can rock them so far that they roll over. With rocking, derailments occur when the cars finally do roll over. With truck hunting derailments occur when an oscillating truck cause so much pressure between a flange and the side of the rail head that it causes a wheel flange to climb over the rail head.
CandOforprogress2Did that once. Went into Cleveland Collinwood yard office after a rough ride on a cold November night. There was some old Hippy Dispatcher behind the desk. Gave him the car number and I got a hot cup of coffee and a donut for my troubles. I think they pulled the car at Willard at the next yard. That was back when it was still Conrail and Conrail was run by old men from Steam Days and there hippie kids. The dispatch office was a busy station with Jitneys going everywhere and union stickers everywere. Now trying to find a human being in a yard is hard. Went thru New Castle PA in Jan2017. not a soul in the crew room. Just a couple of vending machines.
If 'your car' got set out a Willard after being reported at Collingwood, it was during the CSX times - not ConRail.
New Castle was closed as a 'operating yard' prior to my retirement in December 2016. With EHH running the show suspect all yards to be closed and all sidings to be pulled up - that is where it is documented that trains/cars get delayed.
https://www.youtube.com/watch?v=be31Ub3QXbE
Pity the poor hobo in the CN car. yes the door is open
New Castle is still a CC. and there are some cars set off there. New Castle is home to Schnable heavy haul railcars and New Castle Ry which serves the steel mill and transloads PVC
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