Is there a calculator to convert actual weight to your desired scale. for example if a locomotive weighs 190 tons how many grams would that be in HO or N scale?
If the weight of our models scaled down directly, we’d all be in deep distress, as most benchwork wouldn’t be able to support it.
If the weight scaled down directly, a 190 ton (380000 lbs) locomotive would weigh 4368 lbs in HO, 1:87 and 2375 lbs in N, 1:160.
Divide the weight of the prototype by the scale and those are the numbers that result.
No…
you have to consider all 3 dimentions, not just a division of the Weight by the scale. Doesnt work like that.
This topic has been covered many times here on the forums.
David B
A:
Scale weight = prototype weight * (scale ratio)^3
Ex. 190 ton loco:
380000 x (1/87)^3 = .58 lb
So a 70-ton freight car would weigh about 3.4 ounces.
Weight is a 3 dimensional value so you would have to cube the scale, for N scale it would be a factor of 1/4,096,000 (160X160X160).
190 tons x 2000 lbs/ton X 16 oz/lb = 6,080,000 oz
6,080,000/4,096,000 = 1.48 oz
For HO 87 x 87 x 87 = 658,503
6,080,000/658,503 = 9.2 oz
This of course assumes that the density of the material doesn’t change with the scale.
The general conclusion is that its all academic and fun to argue about but really doesn’t have practical application. 
Dave H.
If we could just get wheels and rail that behave exactly the way the full sized stuff does at the greatly reduced loads we’d have it. Well, then there’s the suspension too…
Scale gravity, anyone?
Seriously, this horse has been beaten several turns around the racetrack before.
Chuck (modeling Central Japan in September, 1964)
I do understand where you’re coming from, but there is a sense in which I disagree. I have a photo of some workers rerailing a covered hopper at a chemical plant. These types of derails are not all that uncommon on the prototype. Our object as modelers where wheels, rail and suspension is concerned, is to have our models not act like the prototype in that respect.
Ray
Ok, all you smart guys, what if we model in 1:29th scale? Can we just X3 of your HO figures?
Or is there a figure to use 1:29th in?
thanks, your humble follower.
Most of my 100 ton hoppers are 4 pds and modern passenger cars are10.5 pds.
Physical dimensions scale linearly…that is why a scale Pacific looks like a miniature of the real thing.
Weight is three dimensional, and as stated, is heavily dependant on the density of the material. A 3" cube of balsa wood might weight…3 oz? Dunno. A 3" cube of neutrons would fall rapidly through the soil and try to find the centre of the earth…accelerating much of the way.
So, just for an idea of what happens to a 150 ton Pacific’s weight, you need the cube-root of the weight. That works out to 66 lbs. I guess 1/87th of that result would be an acceptable value for the model, or about 0.8 lbs. Fortunately, my BLI metal K4s is more like 1.2 lbs.
Does that make any sense?
No, and 24389 should be the divisor. (29 cubed)
100 tons is 7.3 pounds. The equation is however an approximation that assumes that there is less material in proportion to the cube of the scale and that molecular distances scale too (which they do not). It’s all fun but moot.
I have to thank you guys for getting this straight for me. A firm self slap in the forehead helped too.
Scale as well as weight is a reduction in three directions. Again with the slap in the forehead and much simplification I was able to figure it out in my head.
A 1:2 scale model isn’t 1/2 of the orginal, but 1/4. Half the length, half the width and half the height.
At 62 I’m still learning, thanks.
Actually, it would be 1/8 (2 cubed). Draw a square and divide it in half vertically, then horizontally. You have quarters. But since you’re talking thickness, too, you also have another layer of 4 segments, giving a total of 8 segments. A 2 inch cube is 8 cubic inches.
[#oops] Absolutely correct, I’m still thinking in two dimensions.