HO scale weight?

[Robert Gift]

What should my Tyco 4-6-2 weigh if its weight were to scale?
How about various rail cars?

Are they now heavier than what the pieces should weigh in scale?

Thank you,

 

[Tuna]

Good question. I'm interested also.

My local hobby shop suggested that cars should weight about 1 oz. per 10 feet of actual car length. i.e.: 80' Pullman = 8 oz. Pullman. I've been doing that with my cars and it seems to work okay.

As for locomotives, I didn't ask so I don't have a clue. Guess I'll have to weight all my locomotives and see how they compare.

 

[CP9302]

Models weigh FAR less than scale. Think about it, at 87lbs at 1:1 would be 1lbs at HO scale.

NMRA practice for HO is 1 oz per car plus 1/2 oz per inch of length. An 89' car should weigh about 7 oz.

 

[FunValleyLine]

Dont know if this helps but it is what I have been going by with my HO layout and have had many less derailments and problems.

http://www.nmra.org/standards/rp-20_1.html

 

[Selector]

This is just rough figuring, but the real Pacific class engines would have weighed, say, 150 tons, not allowing for their many variations, light and heavy.

150 X2000 lbs per ton = 300,000 lbs. HO scale is 1/87 in linear scale, but the weight is cubed in scale (length times width, times also the height), so we need the cubed root of 300,000 lbs. That comes to about 66 lbs.

(66 X 66 = 4356. 4356 X 66 = ~300,00)

I almost bought an HO engine on ebay once that had depleted uranium for weight. It weighed 17 lbs....still a long way to go. (I'm kidding, of course...but you get the point).

The typical HO steamer these days weighs something like a pound and one or more ounces, depending on the type and construction materials. You can appreciate with such a wide separation between what they should weigh in scale and what they actually do weigh that they can only pull a few cars at a time.

 

[Maljunulo]

Take the prototype weight and divide by 87 three times not once.

One to 87 is the linear relationship of the dimensions. The volume and weights need to be multiplied (or divided) three times. If you do this you come out with some halfway reasonable numbers. For example, a NMRA standard 40' boxcar calculates out to about 70 tons. This is not an altogether ridiculous figure, although the "rivet counters" may disagree.

If not, then take the prototype weight, divide by 87 three times, then weight your model to conform. Then not even the most obsessive could fault you.

Cheers!

 

[20rdj04]

weight of car

Thank you for pointing out that weight or mass is cubed not linear. The first time that I tried figuring the weight (Gross/87), I came up with 10 TONS. But dividing by 87.1 cubed is a more manageable 2 pounds, 11 oz. Real world CEBX 800 weight = 1,779,260 pounds.

Again, Thank you.

 

[railfan]

It's pretty amazing how my little single intermountain N scale FP7 can pull 32 railcars of all types, around the track no problem. It's pretty heavy for it's size. It's heavier than a larger atlas SD70MAC with six wheel trucks. These railcars all have plastic wheels. The metal wheels on my bachman container loaded flatcars roll with much less effort.

Mike

 

[cv_acr]

Models weigh FAR less than scale. Think about it, at 87lbs at 1:1 would be 1lbs at HO scale.

No it would not. You're reducing the model in all three dimensions. 87 pounds 1:1 would be 0.0001321 pounds in HO scale.

 

[cv_acr]

This is just rough figuring, but the real Pacific class engines would have weighed, say, 150 tons, not allowing for their many variations, light and heavy.

150 X2000 lbs per ton = 300,000 lbs. HO scale is 1/87 in linear scale, but the weight is cubed in scale (length times width, times also the height), so we need the cubed root of 300,000 lbs. That comes to about 66 lbs.

(66 X 66 = 4356. 4356 X 66 = ~300,00)

I almost bought an HO engine on ebay once that had depleted uranium for weight. It weighed 17 lbs....still a long way to go. (I'm kidding, of course...but you get the point).

The typical HO steamer these days weighs something like a pound and one or more ounces, depending on the type and construction materials. You can appreciate with such a wide separation between what they should weigh in scale and what they actually do weigh that they can only pull a few cars at a time.

That's not correct either. Taking a cube root of the weight doesn't give you any sort of meaningful number. To scale it down you need the scale ratio. Divide 300,000 lbs by the cube of 87 and you get a scale weight of 0.456 lbs.

 

[Selector]

Even that is not correct, CV. What you really need are the mass volume, which comes from linear dimensions, plus the weight per unit of volume for all linear dimensions of all items borne by the rails. From that you can calculate the weight of the locomotive, and then you can do the cubing to estimate if the real item and model are close.

 

[cv_acr]

Selector: it's close enough, you don't need to overcomplicate things. People are simply wanting to know how a prototype weight would translate directly to scale, where the prototype weight is already known or can be researched (through published figures). If you simply assume the same materials and reduce every possible dimension by 87, then the scale weight is a ratio of 1/(87*87*87) of the original.

Consider a perfect cube of a material of uniform density that gets scaled down in all dimensions by 1/87. It will be precisely 1/(87*87*87) of the volume and mass of the original.

Now of course our models are different materials and different dimensions (As close to scale as we try to get there will be significant differences in thicknesses of many parts) so you can just use the scaled down mass of the prototype as a rough comparison.

The method of simply cube rooting the original weight/mass certainly didn't do anything useful because that didn't even use any sort of scale factor.

 

[bennyboots]

I like when this question comes up every once and a while.

 

[tootnkumin]

Working all that out would give me a very heavy head, in 1/1 scale as well.

 

[FCL2117]

Even that is not correct, CV. What you really need are the mass volume, which comes from linear dimensions, plus the weight per unit of volume for all linear dimensions of all items borne by the rails. From that you can calculate the weight of the locomotive, and then you can do the cubing to estimate if the real item and model are close.

The weight per unit volume wouldn't change, though. Steel doesn't magically change its density just because you're working in a smaller scale.

 

[LoudMusic]

I'm going to ignore the craziness of the thread and attempt to answer the original questions And yes I'm aware the thread starter hasn't been here in years.

What should my Tyco 4-6-2 weigh if its weight were to scale?
How about various rail cars?

Are they now heavier than what the pieces should weigh in scale?

Thank you,

Could you be more specific about the 4-6-2 in question?
http://en.wikipedia.org/wiki/4-6-2

Use their prototype weight in pounds and divide by 87.1 three times, then multiply by 16 to convert to ounces.

No, they're probably much lighter than they would be in accurate scale.

You're welcome.

 

[Selector]

The weight per unit volume wouldn't change, though. Steel doesn't magically change its density just because you're working in a smaller scale.

Agreed, and that is why you have to scale it down with the ratio of 1/87 keeping the density, or else your materials change and the scaling becomes meaningless for the purpose of determining if a scale version has the weight to size ratio as the 1:1 version.

You have to know the materials you are comparing. If the model is made of the same components in scale and with the matching materials (or materials of the same density), you can calculate the scale's weight using the scaled dimensions. Our models rarely use the same materials/densities, so that must be accounted for. If either model, faithful replica or semi-faithful model, comes out to 1/87th the weight of the real locomotive, then we could assume they are matched that way as well.

 

[FCL2117]

You have to know the materials you are comparing. If the model is made of the same components in scale and with the matching materials (or materials of the same density), you can calculate the scale's weight using the scaled dimensions.

I may have misunderstood, but I thought the whole point was to determine what the model 'should' weigh, if it was a perfectly scaled version in all respects. In which case, it doesn't matter what materials the model is made of, it 'should' weigh the original weight /87.1^3 (for HO scale).

 

[LoudMusic]

Going back to the ORIGINAL QUESTION ...

What should my Tyco 4-6-2 weigh if its weight were to scale?

Weight / (87.1^3)

 

[railfan]

There are obviously still a few souls who can do math. Perhaps the world will be saved yet. I'm going to take my first intermediate algebra midterm this evening. Please send me some good energy.

Mike