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[quote]QUOTE: <i>Originally posted by cacole</i> <br /><br />Steerable trucks are on some of the newer high-horsepower diesel road engines to help guide them around curves and prevent derailments. With a 6,000 horsepower engine pulling a heavy load uphill, the front wheels in both trucks tend to be lifted off of the rail due to the torque being exerted by the traction motors, and this can cause a derailment on curves. <br /> <br /> <br />[/quote] <br /> <br />I don't think you are correct there... I could be wrong... BUT what I think you are saying is that the traction motors are around the axle and the torque would have the same effect as producing a wheelie on a motorbike... but on a modern loco you have six of them doing it all at once not a single wheel... the power to weight ratio of a loco is also massively diferent from a bike. the leading axle of the leading truck doesn't try to wheelie... nor does the back axle. <br /> <br />What a loco <i>will </i>try to do is keep going in the same direction that it is already going in.. which is always straight on. It is taking the least line of resistance. A curved rail adds a load pushing the loco from it's existing course to another. This is a result of physics doing what physics does. <br /> <br />Steam locos had leading single or two axle trucks to help ease the leading end into curves. I suspect/believe that steerable traucks are doing the same thing. <br /> <br />I think that the word steerable is a bit misleading... the truck doesn't steer in the sense that the front wheels of an auto steer. As far as I know what happens is that when the leading axle is pushed sideways by the rail as a loco moves from the straight to a curve a linkage in the truck flexes the line of wheels from the straight on straight track to a curve which will relate to the curve of the track. This will smooth the ride, reduce wear and assist in the power being put through the wheels to the rail. <br /> <br />The other side of this is that curves are entered through easements... i.e. the curve starts gently. <br /> <br />Slugs are a way of getting all of the power that a single prime mover can put out through the wheels onto the rail... with the result that the train moves. particularly in yards with big slow moving strings of cars making a lot of starts from dead ther is a lot of potential for wheel slip.... so the power is put down through more wheels... it's like four wheel drive in a SUV. <br /> <br />Again,\looking another way. Some very big trains are got rolling with the aid of helpers. these may then cut off on the fly. The train engines are sufficient to keep the train rolling. <br /> <br />A further step of this is that once rolling an engineer will attempt not to stop until he reaches the end of his journey. At imes he might be moving so slowly that you can't see the wheels turning but he will not come to a stand unless he has to.
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