At this current time we are running 75% Micro Train rolling stock on Barleycorn Junction 1999. The M/T cars seem heavier out of the box but I seem to recall they are suppost to be close to the scale weight ? I never found out if this is a true claim ? I guess I would like to know how many tons I'm pulling with a given locomotive ? I can usually pull 13-14 rolling stock ( M/T ) with an Atlas SD60m ( 250' ) up & down long 2* grade without noticing slight struggle except maybe in a smaller radius area ? Anybody know what I'm talking about or do I need to move on ? I wonder sometimes.......... Frog On !
Any weight measured must be scaled up the same way volume would be scaled up since the weight would be due to three dimensional objects, not lines with no thickness or mass. So... 1 gram in N scale would be 160 x 160 x 160 x 1 gram in 1:1 scale, or 4,096,000 grams 4,096,000 grams is 4,096 kilograms (I love metric conversions - we should all go metric) 4096 kg is 9030 lbs. So, for each gram you measure on your scale you're talking about 9030 lbs of scale weight. A 100T (200,000 lb) car scaled down to scale would be just over 22g. Someone is likely going to step in and say my scale up by 160x160x160 instead of just 160 is wrong, but that's not correct.
I'm so glad some people finally understand this. It used to be like pulling teeth to explain it. Next, lets stop saying that N scale is half the size of HO when in fact it's 1/8th the size and layouts don't take half the room, they take 1/4th. Those aren't exact of course since 1/160 is 54% of 1/87 and not 50%, but you get the idea. Jason
I wsa thinking the same thing. Volume increases cubically Using a rough estimate of 400K lbs for the locomotive, using the 160 x 160 x 160 conversion works out to 44.39 grams. [(400,000/2.2) / (160 x 160 x 160) x 1000] Thank you! Area is a quadradic function, not a linear one.
so, for all intents and purposes, 1gm = 4 metric tons. Makes some of those WS people really heavy! A GP40 weighs about 120 tons, but 70 grams would be 280, so we see that even though Adam is correct in his cubed ratio, the weights do not scale appropriately (nor would I expect them to) since material densities would come into play (note my comment on WS people)
Volume and mass are two different things and a ratio is just that, a ratio. I am not sure I agree with the 160X160X160 that is proposed, but it is really a moot point since I don't plan on installing scale house on my layout....LOL!
The 160^3 is exactly correct for scaling, the point of my post is that only works for the same material. Mass = density x volume. For a given material, density is constant, so the mass scales with the volume. But, how many real world cars out there are made of molded styrene, or have plastic trucks, or...? How many locos have a massive block of metal filling them? They don't.
OK, while I'm probably one of the most tractive-effort-beats-everything-else guys, here's why it simply doesn't scale well. 1) Who is buried in Grants Tomb? The equivalent of that is that a 44-tonner actually weighs 44 tons, a 70-tonner weighs 70 tons. Where did they get that from? Many freight cars of the era were 140,000 lb; i.e. 70-tons, so if you could get the loaded freight car over the track you could get the locomotive. There's a lot of bridges out there that max out at 70-tons too, old trestles and pin-connected trusses. 2) Typical GP? Doesn't matter if it is an SW9, a GP9, or a GP40, you can be pretty darn close by figuring 125 tons. If you want the real number, Jerry Brittons PRR site has a ton of railroad clearance diagrams that list wheelbases and actual weights for a lot of PRR-era steam and diesels. Many times the additional wheels on an SD simply reduce the axle loading, not necessarily mean the locomotive is a whole lot heavier, or can even pull more...necessarily. 3) The typical modern freight car limit is 263,000 lbs. on the axles; i.e. 131.5 tons, 100 tons lading + tare of the car. Wait a minute.... the car is heavier than a locomotive??? Yup, it sure is....loaded. What about '286?' That means 286,000 lbs, 143 tons. Make the car lighter = more load. 4) Adhesion sure doesn't scale... because steel-on-steel gets you 25%, add in sand and wheel slip control and you can do a lot better.... Meanwhile I've measured ACTUAL coefficient of friction on every one of my locomotives (documenting my slippery wheel theories) and a GOOD N scale locomotive will do 12-15%, the slippery wheel ones will drop below 10%, and extra axles may actually decrease tractive effort. 5) Tractive effort (TE) on locomotives is measured in pounds; medium steam runs 25-35,000 lbs at the coupler, pay attention to those TE figures. And don't confuse HP with anything, that's a factor of TE at speed, not TE. That's why you 125-ton 3000 hp GP40 kicks a 125-ton SW8. 6) Locomotive ratings are usually in tons for a division, taking grades into effect, directionally. 7) Completely convinced that this doesn't translate, I built a dynamometer car with a spring scale in it and started measuring train resistance, drag, tractive effort, etc., and developed my own system, paying no attention at all to anything else involving math or physics. In my era you're looking at 100-ton cars; 263,000 max loading, so if an Atlas GP7 can handle 8 cars uphill on a 2.5% grade it's good for 800 "tons." The problem rapidly becomes that my Kato GP38 outpulls darn near anything, the model and horsepower have nothing to do with reality or scale. So in the end, you're pretty much right back where you started - stuck at the bottom of the hill irritated with slippery wheels and light DCC frames. I do admit however to having great fun switching a REAL 25-tonner at our local museum and appreciating the physics there; i.e. tiny locomotives and 100-ton cars = CRAP!!! STOP!!! WHOA!!!!
Originally Posted by randgust I do admit however to having great fun switching a REAL 25-tonner at our local museum and appreciating the physics there; i.e. tiny locomotives and 100-ton cars = CRAP!!! STOP!!! WHOA!!!! Got to love the Physics in all this; especially Newtons Law!!! I have also done just a small amount of "real" switching...And CRAP...STOP....and WHOA, are some of the more gentile words that can be used...:startled:....Mike
And lost in all this is the NMRA recommended practice that a N scale car should weigh .5 ounces +.15 ounces for every inch in length. So a 40 foot car [3 inches long] should weigh .95 ounces and a 50 foot car should weigh 1.0625 ounces. I'll let you guys do the math to scale that up to 1:1 tons.
1 oz = 1/16 lbs 1/16*160 = 10 10*160*160 = 256,000 lbs = 128 Tons So, the NMRA is trying to scale the weights reasonably correctly.
NMRA is not recommending the weights based on scaling the prototype weight. They are basing it on performance. http://www.nmra.org/standards/sandrp/rp-20_1.html
And what's lost in that is that standard is 22 years old. In the day of metal wheel, body mount couplers and lower riding cars, the NMRA numbers are completely outdated. What may be even bigger is the absence of Rapido couplers which often had very rigid springs which could pull cars off the track if they weren't weighted on the heavy side. Jason
If you want to have real fun, scale the models UP and things get interesting. All you need is a scale ruler. 1) Axle weight limits are meaningless, we don't break or bend rails when we go over them, so locomotives can be weighted to max. Imagine if a real GP40 was packed full of lead.... Let's say 5 feet wide, 10 feet tall, and 40 feet long of lead, that's 2000 CUBIC FEET of solid lead and that's just the carbody. Figure 708 lb/cu. ft. for lead, that's effectively 708 tons, or well, 5.5 times more than the prototype weighs at 125 tons. Your mileage may vary, but you get the idea. (wow, so that's why we have code 80 rail). And I can't remember the last time I collapsed a bridge except when I sat the case of beer on it. 2) Now take our miserable coefficients of friction for nickel silver to determine TE on the prototype: 708 tons * 15% = 106 tons or 212,000 lbs of TE. Still, wow. The GE ES44AC can do 188,000 lbs starting TE and pretty much peaks out, it weighs 208 tons. Wow....so... the models are HEAVIER than the prototype by scads? Figure out the carbody dimensions and calculate the lead volume in that puppy, probably hit 1000 tons. 3) So a real locomotive that is that much lighter can pull heavier cars than itself and way more cars? Wow.... yeah, that sucks. We're stuck with heavier locomotives, lighter cars, slick rails...and still can't duplicate it in miniature? Wait, I'm getting confused, I don't understand, none of this makes any sense at all.... Exactly.
"Metal wheels, body mount couplers and lower riding cars" are overkill. Too many Ntrak layouts running 100+ car trains for that to be the reason to abolish the standard. Of course Ntrak doesn't run on 9.75" curves either. Maybe using broad curves of 24 inch minimum is a better answer. Even that is a tight curve according to prototype standards. Horseshoe Curve on the NS [old PRR] is a tight mainline curve. It has curves of about 46 inches when scaled down.
If my calculations are correct, Tehachapi Loop would also scale to 46 inch radius if one assumes a perfect circle or its length.
