QUOTE: Originally posted by jcbeard I was just wondering about the scale weight of a piece of railroad equipment. I know that there are the weights recommended by the NMRA for a certain length of boxcar, or tank car etc. But is that the true scale weight? Or would, for instance, in HO scale a prototypical 87 ton railroad car, weigh 1 ton since HO scale is 1:87 scale J C Beard
Is it REAL? or Just 1:29 scale?
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QUOTE: Originally posted by Marty Cozad David Heres a question. A 100 ton hopper, is that gross weight or load weight? And what would a 1:29 scale model be ? Thanks I really don't know
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QUOTE: Originally posted by jcbeard The reason that I asked this question is, It just seems like the size to weight ratio of a model train is different than that of a prototypical train. If my model train hits something and comes to a dead stop quickly, chances my train will probably not come off of the tracks, or very little. But if a prototypical train came to a dead stop from hitting something there would be a large pile of derailed locomotives and railroad cars. J C Beard
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QUOTE: Originally posted by edkowal .....So your model is 10,000 times lighter than the prototype, proportionally. This is the reason that it doesn't behave in the same way as the prototype. When civil and mechanical engineers study models in wind tunnels or water tanks, they have to mathematically correct for such differences, or else their results will be useless. This is true because you can't scale the materials that you use to construct your model. That is, you are using full size metal and wood, with real world densities, to construct your models. The only way that you could get an HO scale car that would behave the way the real world car does would be to magically change the laws of physics for your model railroad room, in such a way that it would cancel out the changes in the volume to linear size ratio. A difficult problem to calculate, and of course impossible to achieve, since the laws of physics can't be changed. -Ed
Mark P.
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QUOTE: Originally posted by tatans "Scale" weight, very interesting question, just why is there a recommended weight for a car? with all the trouble people seem to have pulling a long string of cars(engine slippage) is this weight the actual "scale" weight of the prototype? would it not be practical to make the car as light as possible so the engine can pull more cars? adding weight defeats the efficiency of the locomotive and the slightest incline will stall an engine, the key would be to have a highly efficient motor, a LOT of weight in the loco and pull a long string of very light cars, would this solve the problem? forget "scale" for efficiency, [u]real locomotive are not the lightest equipment around, any comments??
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QUOTE: Originally posted by Brunton You're on the right track ([:D]) Ed, but it's more complex than that. The Kinetic Energy of the model is substantially less than that of the corresponding prototype... ...So, in a collision between a train and a brick wall, the kinetic energy of an exact-scale HO model is reduced from the prototype's kinetic energy by 87.1 (scale ratio) to the fifth power, or by roughly 5 billion times! Meanwhile,stress in materials is calculated as force / cross-sectional area... ...Since stress does not scale, exact-scale HO parts made of the same material as the prototype are over seven thousand times stronger than the prototype. (It's somewhat more than that even, since the smaller a cross-section gets, the closer the material gets to its theoretical strength limit). That probably got kinda deep for some folks, but the upshot is that even exactly-scaled parts are much stronger, proportionally, in the model than in real life. I hope I didn't make a mistake in all that! [:o)]
QUOTE: Originally posted by edkowal Mark: I wanted to do a minimum of number crunching, and not too many examples, because most folks eyes just glaze over when you begin to throw numbers and equations around. Also, I was just too lazy to do the head-scratching necessary to come up with more than one example [:D]. Things like kinetic energy, power generated by motors, dynamics in general, or other quantities that depend on area, volume or other complex relationships don't scale in a linear fashion. That's why I said that you'd have to change the laws of physics to get our models to behave like the prototype does in the full size world. While these posts may have gotten too theoretical for most, the original posting was actually a fairly theoretical question, so it would be hard to give a good answer without it. -Ed
Carey
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