What scale is 4mm as a ratio?

[Blandford1969]

Hello this is a completely daft question for which my apologies. I am trying to get something 3d printed and have been asked what scale 4mm is. Is is 1:72 or 1:76.

 

Once again apologies for a daft question.

 

Best wishes

Duncan

Edited December 23, 2022 by Blandford1969
clarity

[Bucoops]

1:76.2 :)

[ITG]

To a minor degree, the exact answer is affected by how many decimal places you wish to calculate to, but even allowing for that, I’d say mathematically it can never be 1:72. 
Most assumptions start with aligning 305mm to 12 inches, ie a foot. Divide 4mm into 305mm and you get 76.25mm and thus the nearest correct answer to the question asked is 1:76.

 

[Steamport Southport]

OO as used for model railways is 1:76

 

1:72 is used for military, aviation and other plastic kit modelling.

 

 

Jason

[Steamport Southport]

1 minute ago, ITG said:

To a minor degree, the exact answer is affected by how many decimal places you wish to calculate to, but even allowing for that, I’d say mathematically it can never be 1:72. 
Most assumptions start with aligning 305mm to 12 inches, ie a foot. Divide 4mm into 305mm and you get 76.25mm and thus the nearest correct answer to the question asked is 1:76.

 

 

Problem is you are mixing Imperial and Metric, that's why it doesn't work.

 

OO as used in model railways is an Imperial measurement. Correctly it is 5/32 of an inch.

 

 

Jason

[Dungrange]

13 minutes ago, ITG said:

To a minor degree, the exact answer is affected by how many decimal places you wish to calculate to, but even allowing for that, I’d say mathematically it can never be 1:72. 
Most assumptions start with aligning 305mm to 12 inches, ie a foot. Divide 4mm into 305mm and you get 76.25mm and thus the nearest correct answer to the question asked is 1:76.

 

Except that a foot (12 inches) is 304.8 mm, since one inch is exactly 25.4 mm.  Divide 304.8 mm by 4 mm and you get 76.2 (note no units).  This therefore means that expressed as a ratio, 4mm: 1ft is 1:76.2, which is what @Bucoops has highlighted.  Some manufacturers state 1:76.2 on their packaging, others just quote 1:76, whilst some just say 00.

 

12 minutes ago, Steamport Southport said:

OO as used in model railways is an Imperial measurement. Correctly it is 5/32 of an inch.

 

Really?  Maybe back in the middle of the last century before we switched to metric, but I don't think that's the case with the models that are currently produced.  I assume that you are saying that 00 is 5/32 of an inch to the foot rather than 4mm to the foot, which would give a ratio of 1:76.8.  Not radically different, but not the accepted standard nowadays.

[cctransuk]

Pedant alert !!!

 

Many of us should be at our modelling benches, instead of looking for miniscule inaccuracies in the posts here!

 

CJI.

[Quarryscapes]

7 minutes ago, cctransuk said:

Pedant alert !!!

 

Many of us should be at our modelling benches, instead of looking for miniscule inaccuracies in the posts here!

 

CJI.

 

Some of us should even be at work 🤐 😇

[Steamport Southport]

42 minutes ago, Dungrange said:

 

Except that a foot (12 inches) is 304.8 mm, since one inch is exactly 25.4 mm.  Divide 304.8 mm by 4 mm and you get 76.2 (note no units).  This therefore means that expressed as a ratio, 4mm: 1ft is 1:76.2, which is what @Bucoops has highlighted.  Some manufacturers state 1:76.2 on their packaging, others just quote 1:76, whilst some just say 00.

 

 

Really?  Maybe back in the middle of the last century before we switched to metric, but I don't think that's the case with the models that are currently produced.  I assume that you are saying that 00 is 5/32 of an inch to the foot rather than 4mm to the foot, which would give a ratio of 1:76.8.  Not radically different, but not the accepted standard nowadays.

 

See? If you ditch the Metric system you could do away with all those pointless decimal points.

 

The French have a lot to answer for.....

 

[RJS1977]

In any case, 4mm:ft (1mm represents 3 inches) is a convenient way of carrying out the conversion from prototype dimensions to scale (measure in imperial, build in metric!). Dividing by 76.2 or multiplying by 5/32 are more complicated mathematical operations less suited to mental arithmetic...

[Peter Kazmierczak]

I make some of my larger buildings to 3.5mm scale, rather than 4mm. And as for the track gauge...

[kevinlms]

1 hour ago, Dungrange said:

 

.  Some manufacturers state 1:76.2 on their packaging, others just quote 1:76, whilst some just say 00.

 

 

 

With others saying it is OO/HO!

[Dungrange]

52 minutes ago, Steamport Southport said:

See? If you ditch the Metric system you could do away with all those pointless decimal points.

 

The French have a lot to answer for.....

 

No - I don't see!

 

4mm: 1ft is a scale of 1:76.2

5/32": 1ft is a scale of 1:76.8

 

Both have one decimal place - trying to express everything in out of date imperial units solves nothing.  However, as @RJS1977 highlights, 

 

53 minutes ago, RJS1977 said:

4mm:ft (1mm represents 3 inches) is a convenient way of carrying out the conversion from prototype dimensions to scale (measure in imperial, build in metric!).

 

What could be simpler?  It's certainly much simpler than faffing about with 32nds of an inch.

 

The problem is of course that whilst old General Arrangement (GA) drawings will be in feet and inches, the modern equivalent for the current railway fleet will all be in mm rather than inches, so dividing by 76.2 is the most appropriate way of creating a scale model.

[Dungrange]

3 hours ago, kevinlms said:

With others saying it is OO/HO!

 

That's okay if you're trying to sell a tree or ballast, but not really appropriate if trying to sell a scale model.  It could be construed as 4 mm scale, 3.5 mm scale or anything in between!

Edited December 23, 2022 by Dungrange

[Ron Ron Ron]

1 hour ago, Steamport Southport said:

 

See? If you ditch the Metric system you could do away with all those pointless decimal points.

 

The French have a lot to answer for.....

 

 

Ah Ha !!!

You've been outed !

Behind that pseudonym, I reckon you're  Jacob Rees-Mogg .....and I claim my £10 prize !

 

 

 

.

[Michael Hodgson]

49 minutes ago, Dungrange said:

 

That's okay if your trying to sell a tree or ballast, but not really appropriate if trying to sell a scale model.  It could be construed as 4 mm scale, 3.5 mm scale or anything in between!

Trix was 3.8 mm/ft or 1:80

[The Johnster]

For the OP’s purposes, a ratio of 1:76 will result in the printed result being the right size, but it depends to some extent on what the item is.  Buildings, figures, animals, trees, boats, etc. can be allowed a little leeway.  I’ve also used the 3.5mm scale dodge with buildings, notably Walther’s Cornerstone ‘Diamond Coal’ Tippler at my colliery on the current layout, Cwmdimbath.  Looks the part, though the walkways and steps are perhaps a little undernourished, or perhaps I only think that because I’m aware of the discrepancy...  The doorways are the same size as those on RTP and kit 00 buildings 

[TangoOscarMike]

4 hours ago, Steamport Southport said:

 

See? If you ditch the Metric system you could do away with all those pointless decimal points.

 

The French have a lot to answer for.....

 

 

Please don't. I daresay your intention is to be jocular, but jocular casual xenophobia creates an environment in which real casual xenophobia is acceptable, which in turn encourages serious xenophobia.

 

And serious xenophobia is part of the mess that we're all in now.

 

[Il Grifone]

I think we can blame Meccano Ltd. A strictly imperial company, they initially decided on 5/32" to the foot* (Dinky Toy buses are to this scale) but changed early on to 4mm. (no models were harmed by this process!). Some of the dimensions (check out the N2 tank) suggest initial thoughts on H0, but nothing official apparently exists to support this theory.

 

Talking of scale and Trix is rather pointless. their scale was rather approximate at the best of times, though it is obviously smaller than 4mm (at least usually - the buffer spacing is actually slightly larger than 00!).

 

At least in 4mm scale, 3" is conveniently one millimetre.

 

My opinion is that the invention of the metric system immediately rendered the imperial system obsolete and we should be grateful to the French for it. Look up the German inch!

[kevinlms]

8 hours ago, Dungrange said:

 

That's okay if you're trying to sell a tree or ballast, but not really appropriate if trying to sell a scale model.  It could be construed as 4 mm scale, 3.5 mm scale or anything in between!

Perhaps you've never seen an original Airfix wagon kit box!

 

https://www.ebay.com.au/itm/363959579440?hash=item54bdae7330:g:XtEAAOSw7HNh-vZz

[The Johnster]

Back in the day, Airfix were simply following the behaviour of some of the RTR manufacturers, notably Triang, in describing their kits as ‘00/H0’, by which they meant that it could be used on the same 16mm gauge track whatever scale it was to, or was a building or lineside accessory suitable for use with trains running on such track.  IIRC Merit, Bilteezi, and Superquick did this as well despite their output being to 4mm/foot scale.  Trix, ISTR, described their products as ‘00’, which they were, but used a hybrid 3.8mm/foot scale which was arguably more ‘correct’ for use with 16mm gauge track than the standard 00.  

 

00/H0 as a ‘scale’ is a nonsense, of course, you can model in 4mm/foot (and live with the 00 compromise if you don’t want to bother with EM  or S4, which most of us don’t), or in 3.5mm to the foot, but will run into problems if you try to do both on the same layout at the same time.  
 

It was at one time considered of value in marketing RTR and especially train sets to people who might be confused about what 00 and H0 actually were and be dissuaded from buying stuff that would actually run on the same track for fear that it wouldn’t; most of my childhood chums happily mixed Triang TC with 00 on their layouts; so long as the couplings were compatible a train was a train when you were a kid, wasn’t it?  Those of us that were developing enthusiast tendencies out of our trainspotting  and plastic kits looked down our noses a bit at this because we were ‘proper’ modellers (an imprecise term if ever there was one), and of course some of us still do!

[kevinlms]

What is interesting is with the likes of the Tri-ang Transcontinental range, who made some models of overseas prototypes, but to their standard 4mm 'scale'. Later, perhaps decades later, the same models were made by others, but to the correct 3.5mm (HO) scale. Putting them side by side, the Tri-ang version was huge - not even thinking about the bogies.

An example being the Victorian Railways diesel.

 

http://www.hornbyguide.com/article_details.asp?articleid=4

 

 

[Il Grifone]

16 hours ago, kevinlms said:

What is interesting is with the likes of the Tri-ang Transcontinental range, who made some models of overseas prototypes, but to their standard 4mm 'scale'. Later, perhaps decades later, the same models were made by others, but to the correct 3.5mm (HO) scale. Putting them side by side, the Tri-ang version was huge - not even thinking about the bogies.

An example being the Victorian Railways diesel.

 

http://www.hornbyguide.com/article_details.asp?articleid=4

 

 

 

The TC range was  very inconsistent in scale. The passenger cars are H0 scale though short in length (Tri-ang were/are not alone in this aberration - only partly excused by the necessity to traverse sharp curves. Some of the freight cars are H0 and some 00 - all have (crude) 00 bogies. The locomotives are 'fit the box' scale.

'Scale' is at best approximate....

Trix did a rather better job with their U.S. range (within the limits of pre-war tinplate of course).

 

Apologies for grammatical/spelling errors. Whiskers has climbed on my lap and is 'kneading' my arm. He has very sharp claws!

Edited December 24, 2022 by Il Grifone

[JeffP]

10 hours ago, Il Grifone said:

imetre.

 

My opinion is that the invention of the metric system immediately rendered the imperial system obsolete and we should be grateful to the French for it. Look up the German inch

My French friend once tried to tell me this, until I asked him what size the wheels on his car were.

And those on his mountain bike

[Il Grifone]

11 hours ago, JeffP said:

My French friend once tried to tell me this, until I asked him what size the wheels on his car were.

And those on his mountain bike

 

The inch is defined as 25.4mm.

 

The litre and gram are defined in metres or decimal fractions thereof. Therefore there is no need to memorise complicated and irrational tables.

 

Edited December 24, 2022 by Il Grifone