# Converting real life weight to HO scale weight



## OceanRailroader (Jul 26, 2016)

Converting real life weight to HO scale weight.

I'm wondering is it possible to calculate how much someone would weigh in HO scale weight. Such as if I had a goldfish or a bird is it possible to see how much it would weigh if it was a 60 foot long HO scale Goldfish or bird. Or would it be possible to convert how much a person would weigh in HO scale?


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## JerryH (Nov 18, 2012)

HO is 1/87 scale. If you used that ratio for size and weight, a 40 ton loco would weigh 920 pounds in HO scale. A 200 lb man would be 2.3 pounds. That is pretty much impossible even using lead. Then think of the weight a layout would have to support!


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## Old_Hobo (Feb 20, 2014)

OceanRailroader said:


> Converting real life weight to HO scale weight.
> 
> I'm wondering is it possible to calculate how much someone would weigh in HO scale weight


Possible to calculate, but impossible to replicate....and why would you want to anyway......?


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## thedoc (Oct 15, 2015)

JerryH said:


> HO is 1/87 scale. If you used that ratio for size and weight, a 40 ton loco would weigh 920 pounds in HO scale. A 200 lb man would be 2.3 pounds. That is pretty much impossible even using lead. Then think of the weight a layout would have to support!


Unfortunately this is a common but incorrect idea among HO scale modelers. It is true that 1/87 is the ratio for the scale but that only accounts for one dimension, and most objects exist in 3 dimensions. So the real proportion would be to multiply 87 x 87 x 87 which equals 658,503 as the divider, and a 200 lb person would weigh about .0003 lbs, or about .0049 oz. A 40 ton locomotive would weigh about .12 lbs or just under 2 oz. 

Of course this doesn't account for scaling down the atomic structure but then you need to reduce the atoms in both size and weight, and then you are getting into quantum physics, but I think the results would be about the same.


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## thedoc (Oct 15, 2015)

Old_Hobo said:


> *Possible to calculate, but impossible to replicate.*...and why would you want to anyway......?


Yes, in HO scale, the weight would be much too light to be practical.


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## Shdwdrgn (Dec 23, 2014)

thedoc said:


> Unfortunately this is a common but incorrect idea among HO scale modelers. It is true that 1/87 is the ratio for the scale but that only accounts for one dimension, and most objects exist in 3 dimensions.


THANK YOU! I see this error almost every time someone discusses scaling an object's weight (not just in model railroading), and so much of the discussion just goes along with that original assumption. Sure it's easy to see how the original mistake was made, but I'm appalled at times as to how long a conversation will go on before anyone points out the problem.


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## Old_Hobo (Feb 20, 2014)

thedoc said:


> Yes, in HO scale, the weight would be much too light to be practical.


My point exactly!


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## mesenteria (Oct 29, 2015)

Scale can have only two dimensions on a sheet of paper, but the scaled object has three dimensions...length, width, and height. So, if you wish to scale a three dimensional real-world object, you have to scale three ways. Hence theDoc's calculation using 1/87 three times.

It's also why there can't be human giants of the Jack and the Beanstock variety because such a beast couldn't support itself, even with a scaled skeleton. Bones of the human kind wouldn't be able to withstand the forces on it from all the other flesh and connective tissue. The giant's head, alone, would weigh several tons, about as much as a large elephant. So, scaling down the 170 ton 4-8-4 steamer three ways, dividing each dimension by 87, would yield a scale locomotive weighing about as much as a fig. And worth as much on the rails.


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## OceanRailroader (Jul 26, 2016)

I'm also trying to figure out how much would someone weigh in O scale or HO scale if they started off at 165 pounds and grew to were everything around them was HO scale. My question is would to calculate some's weight would it be possible to take their existing weight and times it by 87 times 3. Or times 87 times 3 and take what that equals and divide it by the living thing's weight a 165? 

I'm currently working on a storylines relating to someone becoming a giant and along with several giant creatures. The idea is based off of the idea of Lilliput that Gulliver was a doctor in 1700's Lilliput who saw something happen to someone and he recorded what happened. But after he recorded what happened it was very grim to the point that the King told him to publish a different more cheerful story to make sure people could forget what really happened. But hundreds of years later a guy tricks his brother and his brother's girlfriend to go look for the lost dead giant of Lilliput thinking their is some type of reward or cash prize or movie rights. And naturally the thing that made the first giant is looking for a new host.

The main thing that causes these events and the events in the storyline that takes place in modern times is a thing called self reproducing nano tubes. Nano tubes are some of the strongest structures on earth. Depending on the nano tubes they could allow things like buildings and people to hold up extreme weight.

How this relates to giants is the nano tubes are living and need a host to reproduce themselves. When the nano tubes get into a host's body they merge with the host's cells and use them to take in marital and make copies of themselves. The trouble with the nano tubes is they don't stop multiplying very fast in till the host dies by can't feeding itself anymore. Another thing is the host of the nano tubes becomes almost invincible due to the nano tubes changing around the host's body into a super strong living form. Such as it changes around the body's properties to benefit it.


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## Old_Hobo (Feb 20, 2014)

If you're doing O scale, as mentioned, remember to use a 48 factor, not 87....


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## Shdwdrgn (Dec 23, 2014)

OceanRailroader -- it's an exponent, not a multiplication. It would be 87^3 or 87x87x87 (658503). So take 165 pounds divided by 658503 to get that person's weight in HO (0.000025 pound or 0.004oz). In O scale the factor would be 110592, so their weight would be 0.0015 pound or 0.024oz.


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## JerryH (Nov 18, 2012)

Oops! Forgot about the volume being the critical conversion.


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## traction fan (Oct 5, 2014)

*Why?*



thedoc said:


> Unfortunately this is a common but incorrect idea among HO scale modelers. It is true that 1/87 is the ratio for the scale but that only accounts for one dimension, and most objects exist in 3 dimensions. So the real proportion would be to multiply 87 x 87 x 87 which equals 658,503 as the divider, and a 200 lb person would weigh about .0003 lbs, or about .0049 oz. A 40 ton locomotive would weigh about .12 lbs or just under 2 oz.
> 
> Of course this doesn't account for scaling down the atomic structure but then you need to reduce the atoms in both size and weight, and then you are getting into quantum physics, but I think the results would be about the same.


thedoc;

I don't understand your reasoning here. I'm not saying your wrong, just that i don't get why one would need to do any such math. A 5lb. bag of potatoes and a 5lb. lead weight don't have the same height, length and width; but they still have the same weight. Likewise, A 10lb. sack weighs twice as much, but I don't know that it has exactly twice the physical size. The sacks and lead weight all exist in three dimensions but no one needs to multiply their length, width and height to divide the weight of any of those things. Ten pounds divided by two will be 5lbs. every time. why would 70 tons divided by 87 use a completely different formula?

Traction Fan


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## JerryH (Nov 18, 2012)

Try this. A full size block is 87 inches wide as well as long as well as tall. It has 87 x 87 x 87 cubic inches or 658503 total cubic inches. At 1/87 HO scale it would be only 1 cubic inch. Thus the scaled down unit would weigh 1/658503 of the full size object.


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## Mark VerMurlen (Aug 15, 2015)

thedoc said:


> Unfortunately this is a common but incorrect idea among HO scale modelers. It is true that 1/87 is the ratio for the scale but that only accounts for one dimension, and most objects exist in 3 dimensions. So the real proportion would be to multiply 87 x 87 x 87 which equals 658,503 as the divider, and a 200 lb person would weigh about .0003 lbs, or about .0049 oz. A 40 ton locomotive would weigh about .12 lbs or just under 2 oz.
> 
> Of course this doesn't account for scaling down the atomic structure but then you need to reduce the atoms in both size and weight, and then you are getting into quantum physics, but I think the results would be about the same.


These ratios just don't seem right to me. The outcomes don't feel like they pass the common sense test. I understand the rationale of the 87 x 87 x 87 number, but that's making an assumption that the material density doesn't change with scale, which while true in our modeling, I don't think gives appropriate results. I don't have a better suggestion, so I'm sorry I can't move this discussion forward. I just don't think we've found the right answer yet. Maybe it's a question that really doesn't make sense to ask given that gravity and material science don't really scale at all.

Mark


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## bluenavigator (Aug 30, 2015)

I think that I get it as the image of the cube being that size and scale it down by 1/87 scale. So that mean if the GP40, which would weighs 245,000 lbs. In 1/87 scale, it would been weight around nearly 11 oz? Got it down to 10.93 ounces by calculation.


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## thedoc (Oct 15, 2015)

bluenavigator said:


> I think that I get it as the image of the cube being that size and scale it down by 1/87 scale. So that mean if the GP40, which would weighs 245,000 lbs. In 1/87 scale, it would been weight around nearly 11 oz? Got it down to 10.93 ounces by calculation.



That would be correct but not practical. As has been stated the physics doesn't scale down. As an example many structures built to scale and then scaled up would either collapse or be over built. The physical strength of materials doesn't scale down, and the weight, while it does scale down, doesn't have the same effect, and needs to be increased to have a similar effect.


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## thedoc (Oct 15, 2015)

traction fan said:


> thedoc;
> 
> I don't understand your reasoning here. I'm not saying your wrong, just that i don't get why one would need to do any such math. A 5lb. bag of potatoes and a 5lb. lead weight don't have the same height, length and width; but they still have the same weight. Likewise, A 10lb. sack weighs twice as much, but I don't know that it has exactly twice the physical size. The sacks and lead weight all exist in three dimensions but no one needs to multiply their length, width and height to divide the weight of any of those things. Ten pounds divided by two will be 5lbs. every time. why would 70 tons divided by 87 use a completely different formula?
> 
> Traction Fan


Assuming that the potatoes are all the same density, the 10 lbs would be twice the volume of the 5 lbs but not necessarily twice as high. All 3 dimensions would be increased, the height, the width, and the depth, but not to twice the dimension, just enough to double the volume. If you were to double the size in all dimensions the resulting weight would be 8 times as much. So if the scale were 1/2 the weight would be divided by 8, which is why an object that is 1/87th of full size would be 1/648503th the weight. But as has been stated elsewhere the physics doesn't scale down, so the strength of materials is much greater (which is why HO scaler's can get away with poorly engineered structures that don't collapse), and the weight doesn't act the same. GG-1's and diesel locomotives don't need flywheels on their electric motors, but HO scale locomotives really benefit from them.


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## JNXT 7707 (May 5, 2013)

Which also explains why, if you were a giant, you couldn't pick up a car undamaged like you would a Matchbox car - you'd end up mangling it instead.


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## mesenteria (Oct 29, 2015)

traction fan said:


> thedoc;
> 
> I don't understand your reasoning here. I'm not saying your wrong, just that i don't get why one would need to do any such math. ...Traction Fan


You MUST do the math with three divisions for the same reason that if you only performed two of them you'd end up with a very thin and short locomotive that was still 13 feet tall. Or, a short locomotive that was scaled for height, but still 50 feet long. Or, a thin locomotive that was still 50 feet long and 13 feet high. Every object in space has three dimensions: height, width, and length. If you want to scale any one item, you must scale it in those three dimensions. Scaling is not the same as changing the material properties of the item, or of its molecular structure. You are merely making a scale model of the item.

To illustrate, let us take the thickness of the boiler. It's rolled homogeneous steel of a given quality that is an inch thick to withstand, say, 250 psi. Forgetting about the boiler's length or its diameter, and just taking that boiler plate thickness, you end up with an HO locomotive with a boiler wall 1/87" thick. If made of the same steel, the whole thing properly scaled would weigh something like one tenth of an ounce...ish (I'm making a SWAG). We haven't changed the materials, only their scale. Even filled with real water, and not the heavy metals we use for our toy frames so they will actually pull something, a scaled locomotive would only weigh something like half a pound. A glass tumbler filled with the same quantity of water would outweigh our scale locomotive by quite a margin.


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## thedoc (Oct 15, 2015)

mesenteria said:


> To illustrate, let us take the thickness of the boiler. It's rolled homogeneous steel of a given quality that is an inch thick to withstand, say, 250 psi.


This is the other question that I have not given any though to, but how would you scale the pressure of the boiler? Dividing by 87 cubed would leave you with something quite useless, and the full 250 lbs. would be too dangerous along with being much too high a pressure. It all comes back to the idea that physics doesn't scale down the same as physical dimensions. 250 divided by 87 gives just under 3 lbs. Just out of curiosity, what pressure do the scale model live steam engines run on?


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## CTValleyRR (Jul 26, 2014)

thedoc's last sentence there is the key. If you're talking about PURELY a reduction in dimensions, and the corresponding removal of matter, then yes, the appropriate conversion factor would be 1/87^3 (for HO scale). As applied to a pile of crushed rock, or a sack of potatoes, that would be correct. If you COMPRESS the matter, the mass (notice I didn't say weight) wouldn't change, but matter behaves differently when actually compressed (now you're into astrophysics). If you could somehow reduce an item to 1/87th of it's original size while not affecting it's physical properties or, using the term loosely, operating characteristics, would it weigh 1/660,776th as much? Probably not.

I think the "correct" answer here, as with all other fantasy situations, is the suspension of disbelief. It's a purely hypothetical though exercise, so use whatever answer you find satisfactory for your purposes.


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## Old_Hobo (Feb 20, 2014)

My grade school science teacher taught it this way.....

"What weighs more, a ton of bricks or a ton of feathers?"

Most kids said a ton of bricks.....but, as the weight was a ton for both, they were wrong.....

However, a ton of feathers would fill a very large room, whereas a ton of bricks would fit on a pallet......

So, weight/mass does not neatly coincide with scale/size....


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## thedoc (Oct 15, 2015)

Old_Hobo said:


> My grade school science teacher taught it this way.....
> 
> "What weighs more, a ton of bricks or a ton of feathers?"
> 
> ...


Usually when you scale something down, you use the same material both times. Using different materials is a useless exercise. When you use the same material in both cases, the weight/mass does coincide with scale and size. 

Your science teacher was using a trick question to catch those who couldn't think clearly. If the teacher used it as an example to teach how to think clearly, then it was useful, if the teacher did not, then it was an exercise in futility.


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## Shdwdrgn (Dec 23, 2014)

thedoc said:


> This is the other question that I have not given any though to, but how would you scale the pressure of the boiler? Dividing by 87 cubed would leave you with something quite useless, and the full 250 lbs. would be too dangerous along with being much too high a pressure. It all comes back to the idea that physics doesn't scale down the same as physical dimensions. 250 divided by 87 gives just under 3 lbs. Just out of curiosity, what pressure do the scale model live steam engines run on?


The scaled down pressure is only useless because you haven't scaled *everything*. For instance, consider the friction from resistance -- the effects on a scaled object are huge. The surface of an actual rail is smooth to us, but the surface of a scale track probably looks like going through a gravel pit. The same with air pressure -- your model is still going through the same density of air which may seem like molasses to a scale model.

Put your scale steam engine on a mirror polish track, inside of a vacuum chamber with 87^3 less air pressure, and suddenly that 'useless' steam pressure becomes quite a strong force. It's all relative to the environment you are working within.


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## mesenteria (Oct 29, 2015)

thedoc said:


> This is the other question that I have not given any though to, but how would you scale the pressure of the boiler? Dividing by 87 cubed would leave you with something quite useless, and the full 250 lbs. would be too dangerous along with being much too high a pressure. It all comes back to the idea that physics doesn't scale down the same as physical dimensions. 250 divided by 87 gives just under 3 lbs. Just out of curiosity, what pressure do the scale model live steam engines run on?


The 250 psi is needed to move both the locomotive and tender, but also as much as 2000 trailing tons of loaded freight cars. Our paltry model's foil-thin boiler might withstand 6-10 psi, and considering how light the entire model is, that should be more than enough at the tiny cylinder to move the locomotive. 

I don't honestly know the answer to your question about the boiler pressure in O guage or HO scale live steam, but if those boiler vessels could contain more than about 40 psi I would be surprised. Whatever it is, it is lots, more than is needed to get the entire train under way.


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## thedoc (Oct 15, 2015)

mesenteria said:


> I don't honestly know the answer to your question about the boiler pressure in O guage or HO scale live steam, but if those boiler vessels could contain more than about 40 psi I would be surprised. Whatever it is, it is lots, more than is needed to get the entire train under way.


I was thinking of the larger scales of live steam engines such as 7.5" and 15" gauge, and I know there are people who operate them, I was curious what pressure they used, I don't know off-hand.


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## bluenavigator (Aug 30, 2015)

thedoc said:


> Your science teacher was using a trick question to catch those who couldn't think clearly. If the teacher used it as an example to teach how to think clearly, then it was useful, if the teacher did not, then it was an exercise in futility.


:laugh: Good one!


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