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| Re: Technical Discussion About Axle Journal Bearings (694179) | |||
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Re: Technical Discussion About Axle Journal Bearings |
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Posted by JournalSquare-K-Car on Tue Oct 14 20:12:46 2008, in response to Re: Technical Discussion About Axle Journal Bearings, posted by SilverFox on Tue Oct 14 19:22:25 2008. Umm, there is a flaw in your view. You say that it is better to load the axle closer to the center line...that is kind of flawed, since if you literally laoded the axle at the center, that would put the maximum amunt of torque on it. The most IDEAL place to put the load(from the axle's perspective) is right OVER the wheel itself, so that there will be NO torque upon the axle.Now from lets say you hit a bump on one side of the track on an outboard truck, since the truck is suspended further away from the pivot point, there will be more motion induced on the truck, potentially causing more strain, but suspension can nullify this. An inboard truck will have less pivotal motion since it is suspended closer to the pivot point. Also, in the same situation, an inboard truck will have both bearings raised up if one wheel is raised, while on an ouboard truck, one bearing will go down, while the other goes up, due to the position of the bearings in respect to the wheels, or "pivot/force points." I am also thinking that hollow axles are possible on outboard trucks as well. The bending force, or torque on the axle is caused by the distance from the bearing to the wheel, not whether it is inside, or outside. Maybe inboard trucks allow for the bearings to be closer to the wheel, in which case, they will reduce the bending force on the axle. And the manhattan bridge view of yours is flawed as well. The reason it has issues is that it was initially poorly built. If it were suspended in the center, it would still twist. Like with the axles, the key is to have support over the place of maximum load. or, have the maximum load in between the suspension points, in the case of the bridge. That is why the williamsburg bridge has no issues with twisting; since the trains are in the middle, insted of on the extreme outsides. Plus, the bridge wasn't rigid enough in the first place. But anyways, the torque is still forced upon the manny-b when trains pass over it. Same goes for the Ben franklin bridge, except it seems to have a more rigid design, with less rail traffic, and lighter trains in the first place. Another think to note is that the ben franklin bridge has two cables, instead of four. Maybe those two cables are heavier duty ones than the manny-b's four. |
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