Scale Weight

tatans · September 17, 2005, 5:36pm

What a great bunch of informative responses to this scale weight forum, I must agree with all replies, these questions and responses are exactly what makes this site work, informative, intelligent along with a few laughs, and let us not take ourselves too seriously,-----keep trainin’

Pruitt · September 18, 2005, 7:30am

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

Ed -

It’s been many years since I’ve done these sorts of calculations, and it took me well over an hour to compose the posting and calculate some of the data. Even so, when I was finished I almost cancelled the post, for the same reason you took pains to simplify your explanation. Then I thought “What the heck!” and posted it anyway. There might be some technically-minded folks out there who’s eyes won’t glaze over!

Cheers!

cjcrescent · September 18, 2005, 10:09am

I have to agree with Larry about the RP20. People seem to forget, its NOT a standard. Standards in the NMRA begin with a “S”. Recommended Practices begin with a “RP”.

Many people seem to think that this is law and must be followed. It doesn’t. I know several modelers that add no weight at all to their cars as they want the engineers on the trains to have to think about the problems that can be associated with a couple of real light cars, (empties), coupled between heavy,(loaded) cars or ones located at the head end of a heavy train.

I believe that John Allen also practiced this. (Andy S would know). I think I read somewhere that when he built a new car he didn’t add any extra weight to it at all to bring it up to RP20.