Feb 8, 2021
You're mean ... Then again, probably right...
Na. Not mean. Just life experience I guess. I appreciate all that they do. I just wish sometimes we are not on their wavelength when it comes to explanations. But what you said about weight scaling down makes sense now.
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OK, good info! I knew there was more to it than simply dividing the weight by 160 but wasn't sure on the specific formula. So, we can finally all agree that an N scale freight car wouldn't weigh hundreds of pounds if the weight is scaled-down correctly.
Weight is not scaled by volume guys, sorry to burst your bubble. Weight is a scalar measurement not a volumetric measure. it can be represented as a point source. It includes the load, and the weight of the empty car which is still thousands of pounds. so 31 grams is way way off.
Where did you that? Material has a constant density, which weight divided by its volume. Pounds per cubic inch. So the cubic inch change is the scale factor cubed. Because we are actually are not dealing with a homogeneous object, the actual power is less than 3. A power closer to 2.5 usually accounts for the difference. That is a long way from linear.
Not sure what you mean by "homogeneous object". If you assume constant density and that all components of the object are scaled down proportionately, then it should be 160^3. What's this moose missing?
"Point source"? Weight is proportionate to volume, so don't understand what you're suggesting.
It’s because of the minimums when the object is not homogeneous. Min material thicknesses, fillet radius, etc. Just think of having a 12 in thick steel plate in 1:1 and scaling it down by a 160 scale factor. The 1/2 inch would then be .003. Unrealistically thin. As I indicated earlier, a 2.5 power results in a car weighing 6-8 ounces. Additionally since we are dealing with cars that are mostly plastic rather then steel, the weight will be about 1/6 of the steel part. Around 1 ounce. Actual cars are closer to 0.6 ounce. While not spot on, it’s in the ballpark.
Good enough for GW.
Okay, thank you for the clarification.
Moose had been assuming that the discussion was about proportionally scaling-down every component of the 1:1 object -- structural / systems components, fasteners, fillets, brackets, cup holders, etc.
Seems like you are talking about a visually scaled-down object, designed with n-scale model materials. Correct?
And yes, 2.5 power is good enough for GW! (Moose hasn't heard that phrase since Moose's B-2 days!)
If you guys compared tank cars filled with water, you might be able to get on the same page. At least wrt the weight of the load.
What a rabbit trail! Fun, "I'm late! I'm late! Said the white rabbit as he adjusted his waistcoat and ran off...."
A fun discussion. The cube formula is a good one, but so many other variables get in there. The pertinent ones for us seem to remain, weight (as much as we can get into the loco,) and balance on the traction/pickup wheels. Maintaining good weight on the drivers for pickup of power AND adhesion is a winner. Then the train moves along smartly as slowly or quickly as you like, while we sit back and grin with pleasure!!
Thanks for an entertaining discussion in good civility! Now, if we want to go down to the molecular level.....we do leave bits of the driver's traction tires on the rail every revolution................
Thankfully not everything about our N-Scale locomotives and rolling stock scales downward by the cube-law.
A real locomotive or box car etc. sitting in the sun on a hot day might reach a temperature of 110 Degrees Fahrenheit.
Now divide that 110 by 4,096,000 and . . . is there a temperature below absolute zero?
And so the rabbit trail jumps over to "scale temperatures!" Oooo boy!
If it is worth doing, it is worth overdoing.
No, because some things scale down and some don't. Any thing sitting out on a 110 degree day will experience the same temperature as the atmosphere. However how much heat it retains may differ depending on whether it is painted white and reflects the suns rays or black and absorbs the rays. Radio control aircraft fliers know that lift of a wing depends on the number of air molecules involved. But air molecules do not scale down as does a wing. So even though the model plane weighs less than the prototype it still needs an over sized wing to generate the needed lift. Scaling down the weight of a prototype car by adding the weight of the car plus the weight of the load and finding the cube root seems logical and in the example presented previously is in line with the NMRA recommendations for weighting N scale cars.
Something sitting out in the sun will get hotter than the air temperature. How much hotter depends on many factors (reflectivity at IR wavelengths, shaded surface area and airflow for cooling,) but it will be somewhat hotter. Cold surfaces do not radiate "cold", they just radiate less heat, and they absorb more heat, all else held equal.
Ever touch the polished chrome on a HOT sunny day? Ouch! And now the finger, arm or whatever touched it is cooked by metal a lot hotter than the air around it.
Well thank you so much for what you have provided! I will have to download this and do my own comparison with it. I myself enjoy the physics of actual rail traffic with pulling/stopping/starting of equipment. You have earned a great respect from me. Thanks again Moose!
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Thank you for the compliment, good sir! And it sounds like it should prove an interesting read for you...
And just for fun...
If you are interested in other FRA publications or information, see the following:
If you are interested in Code of Federal Regulations for Railroads, see Title 49, Volume 4, Chapter II of the following:
AND, no, please do not attempt to scale down any CFR or FRA documents or regulations by a factor of 1/160^3 for use on n-scale model railroads.
I normally don’t wear reading glasses, but I use my 4+ readers to inspect and work on my trains. My eyes are approaching the big 50 in a few months. My word! I don’t want to be that technical in modeling my trains!
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Somebody who really really wants to build and operate a model railroad "realistically" needs to memorize and absolutely adhere to the CFR's for railroads. Otherwise, they're not modeling a railroad correctly...
Sorry, that was an obscure dig at a recently banned member of another forum. Please, do not take this statement seriously...