I'm not too familiar with truck designs other than good-old journal box in pedestal types. I never gave much thought to the role of longitudinal clearances having an effect on hunting threshhold speeds. I believe that EMD and GE always gave maximums - at which point you'd replace pedestal liners on a locomotive truck - but not minumums. There may be some relationship, but I don't know what it might be.
Two big drivers of hunting threshold speed are the bolster center length and wheel taper. The greater the bolster centers are the better, and the closer to cylindrical, the better. What happens when a wheel wears is that the effective taper gets greater, so the hunting threshold speed comes down.
Where is Bogie Engr when we need him! Maybe he only sails the seas of the Locomotive forum...?
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
The journal boxes slide up and down in the pedestals. There are normally "ears" of some sort that constrain the box laterally in the pedestal. The pedestal normally has some sort of wear plate on it, but there is only a small amount of slop laterally. The spring that fits on between the journal box top and the truck frame provides very little lateral suspension. The secondary suspension (bolster to truck frame) provides nearly all the lateral suspension.
If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
Paul Milenkovic KCSfan walter prr Side to side Soumds like you were in a car that was "hunting". If this lasted throughout the trip at higher speeds this was almost certainly the case. Mark Worn wheels can do that. And worn rail heads. So can worn trucks. It seems that Superliner I's had this European-style truck that used automotive-style radius arms to keep the axles aligned. The Superliner II's and Horizons have a more conventional style of truck where the axles move in slots of the truck frame. Does some kind of device go in that slot to apply centering force to the axles? Amfleets, according to Don Oltmann, connect the axle bearings to the truck frame with slabs of synthetic rubber. For some reason, Amtrak likes the conventional style of swing hanger truck that uses -- are they called pedestals? -- slots in the truck frames to guide the axles and springs and drop equalizers (like the AAR Type B locomotive truck). But I think I have heard more rough riding stories from Superliners (do they all now have those "conventional" trucks?) than about Amfleet.
KCSfan walter prr Side to side Soumds like you were in a car that was "hunting". If this lasted throughout the trip at higher speeds this was almost certainly the case. Mark
walter prr Side to side
Side to side
Soumds like you were in a car that was "hunting". If this lasted throughout the trip at higher speeds this was almost certainly the case.
Mark
Worn wheels can do that. And worn rail heads.
So can worn trucks. It seems that Superliner I's had this European-style truck that used automotive-style radius arms to keep the axles aligned. The Superliner II's and Horizons have a more conventional style of truck where the axles move in slots of the truck frame. Does some kind of device go in that slot to apply centering force to the axles? Amfleets, according to Don Oltmann, connect the axle bearings to the truck frame with slabs of synthetic rubber.
For some reason, Amtrak likes the conventional style of swing hanger truck that uses -- are they called pedestals? -- slots in the truck frames to guide the axles and springs and drop equalizers (like the AAR Type B locomotive truck). But I think I have heard more rough riding stories from Superliners (do they all now have those "conventional" trucks?) than about Amfleet.
walter prr That sounds right. It was consistent throughout the trip at higher speeds.
That sounds right. It was consistent throughout the trip at higher speeds.
The other thing to consider is you'd notice side to side motion more on the upper level than the lower. If you consider the bolster as a rocker point, you'll feel much more motion on the upper level than the lower for the same amount of "rock."
I vote truck hunting due to worn wheels! It can give you kind of a rhythmic sloshing back and forth feel. The secondary suspension (bolster to truck frame) will dampen the real nasty flanging action going on. (freight cars are not so lucky). It'll occur most on long tangent, high speed streches and should calm down for a minute or so (or more) after going over a switch or thru a curve.
When people file such reports on rough riding, perhaps it may be interesting to report if the problems are with isolated cars or throughout the consist. If the problem is wheel and truck maintenance, one would expect some cars to ride rougher than others.
By "jerky," do you mean front to back, or side to side?
Took my second Auto Train trip recently. My first was about a year and a half ago. Found the latest trip to be very jerky. The first trip seemed much smoother. Was on the lower level of the Superliner coach the first time and on the upper level the second time. Is the difference in the quality of the ride due to seat location, track deterioration or all of the above?
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