I was working on a boxcar and I broke a detail part, and I sighed and the car tipped over. This got me thinking about scale weight. If I am right, a 100 Ton car in HO scale would weigh 1.14 tons!!! Here is my math… 100/87=1.149 . Is there a step that I missed or is this correct?
well if a HO scale car weighed that much, there would be no point to the hobby except weight-lifting. in reality, the National Model Railroad Associatoin has freight car standards for the weight depending on the length. i’m unsure about the weight standards though.
BTW do you mean pounds, because that sounds a little more accurate to me.
just my thoughts…
I am saying if we took all aspects of a real car and scale it down.
oh…
No…your math is wrong. This has been covered before.
David B
Pfft, thanks for the indepth explanation there.[#dots]
Mass does not scale linearly. It scales as the cube of the values. If you have a mass 5 inches on a side (5X5X5) with a density of “1”, then its mass is 125 of those density “1’s”. You need to derive a cubed root of the 100 tons to get the real “scale.”
The 1/87 rule applies to size (feet, inches) and not to weight. That calculation would have to take onto account the density of the materials. I missed the earlier posts but it would be interesting to see the complete calculation.
Joe
Thanks that makes sence(sp?). So it would be more like this?
Wm = Wp / 41,298.5 = 200,000 lb / 41,298.5 = 4.85 oz.
No, it’s not correct. An HO model is 1/87 in all 3 dimensions, so the weight (assuming same construction materials as prototype would be 1 / (87 * 87 * 87) of the weight of its prototype. That’s 1 / 658503.
A 100 ton capacity car has a tare (i.e unloaded) weight of around 20 tons, so a fully loaded 100 ton car would weigh about 240,000 lbs (3,840,000 ounces). A model of that car would weigh 5.8 ounces assuming all else was equal.
The engine and tender weight of a UP Big Boy was 1,208,750 lbs. An HO scale model built with identical materials in scale would weigh about 1.83 lbs. However, we like to add weight to our models and lead does have a much higher density than steel.
Hope this helps.
Andre
You need to reduce all three dimensions. Weight is a function of volume and density. In the case of the 100 ton boxcar you divide (100 tons * 2000 lbs) by 87**3 (87 cubed). In this case the answer is about a third of a pound.
Let me know if you need more detail.
Enjoy
Paul
Interesting to note that the value 4.86 ounces (my result) is remarkably close to the NMRA recommended weight for a 100 ton (loaded weight) box car. OTOH, my “standard” car (24 tons loaded) would come out to only half the NMRA recommended weight for its length (1,65 oz vs 3+ oz.)
Chuck (modeling Central Japan in September, 1964)
Well, you scaled the length of the car but you didn’t scale the heighth or width; you now have a car 6¼ inches long by ten feet wide by fifteen feet tall and that might just weigh 1.14 tons. Now take 100×2000 (lbs per ton)×16 (ounces per lb)÷87.085 (scale length)÷87.085 (scale heighth)÷87.085 (scale width) and you should come up with something in the ballpark of five ounces.
I know a guy who, when he was seven, was three feet tall and 18 inches around the waist and weighed fifty lbs. When he was eighteen he stood six foot tall and was 36 inches around the waist and weighed two hundred lbs. He hasn’t gained any in heighth but his girth is now seventy two inches and he weighs - are you ready for this? - four hundred lbs. Every time something doubles something else doubles. When heighth and girth both doubled weight quadrupled.
I believe that the 100 ton weight includes the weight of the empty car. The 100 tons is based on the capacity of the trucks. So the car can carry a load of whatever the difference between the weight of the car and 100 tons is.
I agree, it is interesting. I think it shows that the NMRA weight recommendation isn’t really scaled down from the prototype. Of course our models behavior isn’t exactly scaled down either. But we are in the same ballpark.
Enjoy
Paul
The NMRA weight recommendations were developed after extensive testing for reliable operation. Scaling down the actual weight of a car didn’t really come into it. SOme cars do happen to work out to close to what the scaled down weight it, but that’s more luck than anything.
The scale ratio applies to linear dimensions. So 87 real feet is 1 foot in HO scale. Areas, liek square feet, acres, etc. need the scale ratio to also be squared, so to convert 1000 sq ft to HO you need to divide by 87 squared, not 87. Weight and volume are cubic measures, so the scale ratio must be cubed. Thus to convert 100 tons to HO scale you would divide by 87 cubed.
–Randy