Can you scale down weight?

[frobisher]

No. You can scale mass but weight no because you can't scale time in any simple manner that can be represented on a model railway.

Not really. Time doesn't/shouldn't scale within the Newtonian model, however because we can't produce a scale gravity to get meaningful scale behaviour within our normal 1g gravitational field, you need to apply a scale factor to passing time to get equivalent results, which then has a whole bunch of knock-ons not least of which is to scale speed.

 

Technically speaking, if everything else is correctly scaled, then the scale weight of a 50tonne object is in fact 50tonne. We use mass and weight equivalently in normal life because we don't in general experience varying gravitational fields and rely upon the 1:1 relationship between the force reading on a set of scales and the mass of the object placed on them.

[meil]

Not really. Time doesn't/shouldn't scale within the Newtonian model, however because we can't produce a scale gravity to get meaningful scale behaviour within our normal 1g gravitational field, you need to apply a scale factor to passing time to get equivalent results, which then has a whole bunch of knock-ons not least of which is to scale speed.Technically speaking, if everything else is correctly scaled, then the scale weight of a 50tonne object is in fact 50tonne. We use mass and weight equivalently in normal life because we don't in general experience varying gravitational fields and rely upon the 1:1 relationship between the force reading on a set of scales and the mass of the object placed on them.

Yes in normal use mass and weight are confused in peoples mind but unfortunately weight affects the dynamic response and therefore you cannot ignor the difference when dynamic systems are being modelled. To our 1:76 scale world gravity appears to be some 8 times stronger than it is in our real world.

[leopardml2341]

That explains why one can never find the bits that go 'ping' from the modelling table - they are being pulled towards earth with a force 8 times greater

[Grovenor]

 

 

To our 1:76 scale world gravity appears to be some 8 times stronger than it is in our real world.

And how do you arrive at that nice simple number?

Regards

[mikesndbs]

That explains why one can never find the bits that go 'ping' from the modelling table - they are being pulled towards earth with a force 8 times greater

 

That is so very true, I have always said there was extra gravity now I know its true lol

[mikesndbs]

Let me re pose this question.

 

If I have a 1 ton solid lead block, how much would a 1/76 scale solid lead block weigh?

 

Thanks

[BlackRat]

You could always use spent uranium as extra weight to your wagons, as a bonus the layout room wouldn't need lighting either.

[Revolution Ben]

 

Hi there,

 

Our Revolution Trains crowd-funded TEA tanker in N is being manufactured to NMRA standards for weight. These are half an oz plus 0.15oz for every inch in length.

 

The wagon is 132mm long, and converting all that to metric gives a weight of 34g and when I checked the recently delivered test samples this was their weight.

 

Now the prorotype is a 100tonne gross weight, and British N scale is 1:148. When divided by the cube of the scale, we have 100,000,000 / 3,341,792 ~ 31g.

 

This isn't too far off, but I suspect is more of a happy coincidence as I doubt when creating their standards the NMRA was trying to replicate scale weight, rather give a weight that would ensure decent running!

 

cheers

 

Ben A.

[57xx]

You could always use spent uranium as extra weight to your wagons, as a bonus the layout room wouldn't need lighting either.

 

I have heard of teams in US Pro Stock drag racing using depleted uranium to add ballast to their bikes to bring them up to the minimum class weight. Not something I'd want to be machining to fit!

[Reorte]

Let me re pose this question.

 

If I have a 1 ton solid lead block, how much would a 1/76 scale solid lead block weigh?

So if the question is: Take one cube that weighs a ton, how much does one with an edge 1/76th as long weight? The answer is less than a tenth of an ounce (35840 ounce in a ton / (76*76*76) ).

 

The material doesn't matter although a ton of styrofoam is obviously a lot bigger than a ton of lead. The considerations about the scale effects of gravity and so on only matter if you want scaled down behaviour, i.e. things fall at a scaled rate, but then you're into all sorts of complexities as material behaviour is completely different too.

[Blacque Jacque]

Let me re pose this question.

 

If I have a 1 ton solid lead block, how much would a 1/76 scale solid lead block weigh?

 

Thanks

2.27 g

Although you said ton, my calculation was based on metric tonnes, so olde English would be a little different

 

Edit typed Kg through force of habit

[Chimer]

Let me re pose this question.

 

If I have a 1 ton solid lead block, how much would a 1/76 scale solid lead block weigh?

 

Thanks

 

I refer the hon gentleman to the answer I gave earlier ...... 

 

If you produce a 1:76 model of something made out of a single uniform material (e.g. a wooden sleeper) in the same material, the weight/mass (forget the difference and not worried) will be 1/(76*76*76) of the original weight/mass.  But as far as I am aware, nobody has ever built a model of a loco using the same material as the original for every component - probably because it wouldn't go 

 

And in this simple case at least, time and gravity, and any necessity/inability to scale them, are irrelevant.

[mikesndbs]

I refer the hon gentleman to the answer I gave earlier ...... 

 

 

And in this simple case at least, time and gravity, and any necessity/inability to scale them, are irrelevant.

 

 

Explain this calculation a bit for me please 1/(76*76*76) of the original weight/mass. is that 1 divided by 438976? and what is the result in fraction of ton or ounces? 

 

Thanks

[Blacque Jacque]

Yes it is 1/438976.

 

1/76tth scale represents a single dimension, since our models are 3 dimensional, we must apply that division to each of the dimensions, hence 1/438976.

 

To use your lead example (in metric again, sorry);

 

Lead has a density of 11.342g/cm³

1 metric tonne of lead (1000Kg or 1 million grammes) = 88167cm³ or a cube of 44.5cm on each side.

Scaling that cube to 1/76th gives a cube of 0.585cm (or 5.85mm) per side (44.5 / 76)

That cube's volume is therefore 0.2 cm³ (or 0.585 * 0.585 * 0.585)

Multiply the volume by the density to get the weight:

0.2 * 11.342 = 2.27g

[34theletterbetweenB&D]

 
 

Explain this calculation a bit for me please 1/(76*76*76) of the original weight/mass. is that 1 divided by 438976? and what is the result in fraction of ton or ounces? 

 

Division by the cube of the scale ratio, gives the scaled down weight/mass. Using 76.2 as the scale ratio for OO

 

Metric system, reckon 2.3g per ton

 

Imperial measure, reckon 1 ounce = 12.5 tons

 

[dhjgreen]

Yes it is 1/438976.

 

1/76tth scale represents a single dimension, since our models are 3 dimensional, we must apply that division to each of the dimensions, hence 1/438976.

 

To use your lead example (in metric again, sorry);

 

Lead has a density of 11.342g/cm³

1 metric tonne of lead (1000Kg or 1 million grammes) = 88167cm³ or a cube of 44.5cm on each side.

Scaling that cube to 1/76th gives a cube of 0.585cm (or 5.85mm) per side (44.5 / 76)

That cube's volume is therefore 0.2 cm³ (or 0.585 * 0.585 * 0.585)

Multiply the volume by the density to get the weight:

0.2 * 11.342 = 2.27g

*pedant mode on*

K=Kelvin (absolute degrees) or kilo, as in Bytes (just checked your profile)

k=kilo for other units

*pedant mode off*

[tersono]

Not really. Time doesn't/shouldn't scale within the Newtonian model, however because we can't produce a scale gravity to get meaningful scale behaviour within our normal 1g gravitational field, you need to apply a scale factor to passing time to get equivalent results, which then has a whole bunch of knock-ons not least of which is to scale speed.

 

Time is an illusion. Lunchtime doubly so.

[sharris]

I often wonder why the P4 leccy people don't use an accurately scaled down voltage.

As for scale weight, the first thing to fix is a change in gravity in the railway room.

Bernard

 

The third rail chaps would be ok at about 8 volts, but the 328 volts for overhead wires would certainly discourage finger poking at exhibitions!

[runs as required]

In building design, despite computers, it is still good practice to actually physically design by trial and error - building 'sketch models' almost as quickly as you think - typically using timber and card (that one can easily warp/bend) to a useful scale size - say 1:50.

Because of the general 'scalability' of structural principles, particularly if you are using timber of a density (rather than balsa) similar to structural timber, one can readily comprehend what will be the structural behaviour of an equivalent 'real' builidng.

The advantage is that you can still keep and express the 'materiality' of the building compared to one entirely generated in a computer.

 

Its a 3,000 - 5,000 year old art in China with the various traditional timber 'orders' -  and in the Middle Ages when they were outdoing one another daring to to go higher and wider they built models to simulate complex masonry rib vaulting and 'hammerbeam' roofs.

 

Supreme in his understanding of such 'scalability' on our forum is Ron Heggs. Have a look and enjoy his 1:76 scale (00gauge) models here:

http://www.rmweb.co.uk/community/index.php?/gallery/member/10633-Ron%20Heggs/

 

dh

[Reorte]

Time is an illusion. Lunchtime doubly so.

You ought to send that in to the Readers' Digest. They've got a page for people like you.

[tersono]

You ought to send that in to the Readers' Digest. They've got a page for people like you.

 

LOL!

 

More than likely.

[meil]

And how do you arrive at that nice simple number?

Regards

It's the square root of the scale. OK 8 is the square root of 64 which is S scale.

 

For 4mm it's 8.7

[Pacific231G]

You ought to send that in to the Readers' Digest. They've got a page for people like you.

It must be Thursday. I never could get thehang of Thursdays.

 

The whole thing about scaling is that it changes the behaviour of an object. Some things scale linearly such as the length of an object, some scale as a square, others as a cubic function and some to even higher powers*. This means that a small scale model behaves very differently from its full size equivalent; it's also why elephants have proptionally thicker legs than sheep, large birds have proportionally bigger wings compared with their bodies than small ones (as do aeroplanes) and there's no danger of ever meeting a thirty foot spider.

 

Model railway vehicles never behave exactly like their full size counterparts and things like the swaying of  a model coach as it passes over a set of points or the motion of loose coupled wagons will always be unrealistically fast simply because you're not scaling time and the accelaration due to gravity is a constant. 

You can see this effect very clearly in this clip

https://www.youtube.com/watch?v=RlbfRtWUyeU

If you want to use model railways in a film then you need to use a fairly large scale but here you can scale time by running the trains at a fraction of their scale speed but with with a slowed down camera. 

I think this may be what Hitchcock did with some of the shots in the 1938 version of  "The Lady Vanishes". This makes a lot of use of beautifully made models.

http://3.bp.blogspot.com/-t3UI80vqtj0/VSQr0TCOmPI/AAAAAAAAByQ/upEDSBUwIqE/s1600/LadyVanishes1.png

 

The complete terminus and village in the opening shot which doesn't include any railway movement does look like a model, possibly in O scale, especially when a car is pulled through the street (the terminus wouldn't be a bad model railway) Some of the closer shots look to be about gauge one.  

http://hopeliesat24framespersecond.files.wordpress.com/2012/05/large_the_lady_vanishes_blu-ray_1x1.jpg

 

 

*the damage done by wheels on a road is proportional to the fourth power of the weight on them so If you double the axle loading of a truck the damage it does to the road is about 16 times as great and a "modest" 15% increase in axle weight will double the damage.   

[meil]

Yes it is 1/438976.

 

1/76tth scale represents a single dimension, since our models are 3 dimensional, we must apply that division to each of the dimensions, hence 1/438976.

 

To use your lead example (in metric again, sorry);

 

Lead has a density of 11.342g/cm³

1 metric tonne of lead (1000Kg or 1 million grammes) = 88167cm³ or a cube of 44.5cm on each side.

Scaling that cube to 1/76th gives a cube of 0.585cm (or 5.85mm) per side (44.5 / 76)

That cube's volume is therefore 0.2 cm³ (or 0.585 * 0.585 * 0.585)

Multiply the volume by the density to get the weight:

0.2 * 11.342 = 2.27g

Unfortunately you are confusing mass and weight.

 

Volume x density gives you mass. Weight is mass x g. So your block a lead would have a mass of 2.27g here and anywhere else in the universe but it would only have a weight of 0.0223N here on earth. On the moon it would weigh only 0038N but still have a mass of 2.27g.

[John_Miles]

A simple way of looking at this is by asking why your model train doesn't need the sort of stopping distance that a real train does. Also when it falls off the track, why doesn't it smash itself and the scenery to pieces. The answer is that in our models we scale length so that models look right. We don't scale mass so we don't have the correct momentum in our trains so they don't require huge stopping distances. If you scale mass, say at 4mm to the foot, then your locos should weigh something around a ton. That would test your baseboard and there is no material dense enough to achieve this mass. Any form of scaling is always a compromise. With any form of scaling you can scale part of the problem but not all of it.