Model Railway Forum banner
1 - 20 of 60 Posts

·
Registered
Joined
·
8 Posts
Discussion Starter · #1 ·
Hi folks, new to this forum, and new to OO scale model railways (but not new to modelling).

I have a question about OO scale conversion. I am currently putting together a simple OO Scale Calculator program that will work on a web page and on the desktop, to speed up converting actual measurements into OO scale.

I understand that OO scale is 1:76, however I have also been told that 4mm = 1 foot and 13mm = 1 metre. The problem is that these are not all to the same scale.

1 foot @ 1:76 scale = 4.01mm, so it's fair to say 4mm.

However 1 metre @ 1:76 scale = 13.15mm, which means that over longer distances, using only 13mm instead of 13.1mm or even 13.2mm the scale model will become progressively too short.

How do you deal with this? Do you think it matters? Do you use 13mm or 4mm? Or do you divide by 76?

Am I being too picky? Ordinarily I would probably use either and not worry too much about being a couple of mm out over a longer distance, but since I am now putting together a program to make calculating quicker, it suddenly seems to matter since it will give me a result to several decimal places.

What are your thoughts?

Happy to let you all have a copy when I am done (already have a prototype running based on 13.1mm to the metre).

Thanks in advance.
 

·
Chief mouser
Joined
·
11,775 Posts
I have to admit I'd never heard of 13mm = 1 metre, so obviously I have never used it.

Personally I would stick to using 4mm = 1 ft.

Regards
 
G

·
Hiya

Ignoring that 00 isnt a scale (its a gauge) the scale in question is 1:76.2 not 1:76. So in answer to your question i always use mm and divide by 76.2 thus 1 metre scales out at 13.123mm and a foot (304.8mm) scales out at dead on 4mm.

At the end of the day its just numbers so when drawing things up for print or etch I always work to 0.001mm

Cheers

Jim
 

·
Registered
Joined
·
4,497 Posts
I believe the 'Official' definition of 00 scale is that 4mm=1ft. Bear in mind too that most drawings of British prototypes (until the 1970s) are marked in feet rather than any metric measurement, I would stick with the 4mm=1ft as well.

Regards,
John Webb
 

·
Registered
Joined
·
8 Posts
Discussion Starter · #5 ·
Thanks Britho, and also Jim for the correction on 1:76.2.

I see from your comment Jim that some people would find results with plenty of decimal places helpful for drawing up more accurately.

I will adjust my formula for 1:76.2.

Based on responses from this forum and others I have pretty much decided to make it so that users can select the scale they want (e.g. 1:76.2, 4mm = 1 foot, 2mm = 1 foot (N gauge) and etc). That way it still speeds up the calculation process (the aim of the program), but gives them the answer they would have got working their way in the past.

Any other suggestions gratefully recieved. Should have a prototype running tonight, will post a link to it on this thread.

Thanks for your responses.
 

·
Registered
Joined
·
8 Posts
Discussion Starter · #6 ·
"Bear in mind too that most drawings of British prototypes (until the 1970s) are marked in feet rather than any metric measurement".

This is a very good point John. I will make sure the program allows users to input Metric or Imperial actual sizes and get the scaled down result in mm.

Thanks for that observation.
 

·
Registered
Joined
·
999 Posts
Do you think that one is needed?

I'd have thought that any modeller with a little simple arithmetic and a little spreadsheet knowledge can easily devise the required formula in a spreadsheet knowing that 4mm = 1 ft.

I spent an hour or so over Christmas scaling a photo down to 4mm scale in preparation for a loco scratchbuilding project. Knowing the prototypical dimensions of three pieces of data in the photo it wasn't hard to devise the necessary formulae in one cell and replicate it as many times as I needed.

If you're going to do it, why not make it universal and equip it for O, HO, TT, N and Z gauges as well, and why not go the whole hog and include the latest microscale gauge "T" which I believe is 450:1.

Anyway good luck.

Keith.
 

·
Registered
Joined
·
8 Posts
QUOTE (GoingUnderground @ 2 Jan 2009, 16:46) <{POST_SNAPBACK}>Do you think that one is needed?

I'd have thought that any modeller with a little simple arithmetic and a little spreadsheet knowledge can easily devise the required formula in a spreadsheet knowing that 4mm = 1 ft.

I spent an hour or so over Christmas scaling a photo down to 4mm scale in preparation for a loco scratchbuilding project. Knowing the prototypical dimensions of three pieces of data in the photo it wasn't hard to devise the necessary formulae in one cell and replicate it as many times as I needed.

If you're going to do it, why not make it universal and equip it for O, HO, TT, N and Z gauges as well, and why not go the whole hog and include the latest microscale gauge "T" which I believe is 450:1.

Anyway good luck.

Keith.

Thanks Keith, good points all round.

I suppose I originally started making it just for me, a quick app to save me using the calculator everytime (though I had not considered a spreadsheet at the time I could use the same formulas to put one of them together).

Then I thought that other people might find some benefit from it so I started making it more attractive to use, and more like a professional program, as well (ex-web and multimedia designer you see - now teaching). Christmas hols is great time to run away with personal projects I guess.

I love the idea of making it universal, definately going to do that in the next version. Should have my initial prototype online tonight, will post a link.

Thanks for the suggestions.
 

·
Registered
Joined
·
1,628 Posts
Going back to the original post, even if you use 13mm = 1m the discrepancy will only be around 1mm for every 9 metres of prototype (using the measure 1 metre = 39.37 inches, so add approximately 1 inch for every 3 metres, or 3 inches - a scale 1mm - for every 9 metres). OK, so the longest coaches on British railways are around 23m, so you will be between 2 and 3 millimetres short in the final outcome, if you don't make any corrections. For purists that would be disastrous; for me ... who cares! I'm not going to notice 2mm missing from a 23m coach, especially when it is in service on the tracks.


Add to that that we're dealing with modelling compromises anyway, such as the scale 6 foot (sorry; 2 metre!) gap between coaches or wagons, or locomotives and tenders, and we can easily explain away the slightly shorter physical length. Hell, I don't even mind the Heljan "Tubby Duff"; in fact, I like it very much. The extra width does show from some angles but overall it still looks like what it is supposed to represent, a class 47 Brush type 4!
 

·
Premium Member
Joined
·
1,303 Posts
QUOTE (SRman @ 3 Jan 2009, 09:23) <{POST_SNAPBACK}>Going back to the original post, even if you use 13mm = 1m the discrepancy will only be around 1mm for every 9 metres of prototype (using the measure 1 metre = 39.37 inches, so add approximately 1 inch for every 3 metres, or 3 inches - a scale 1mm - for every 9 metres). OK, so the longest coaches on British railways are around 23m, so you will be between 2 and 3 millimetres short in the final outcome, if you don't make any corrections. For purists that would be disastrous; for me ... who cares! I'm not going to notice 2mm missing from a 23m coach, especially when it is in service on the tracks.


Add to that that we're dealing with modelling compromises anyway, such as the scale 6 foot (sorry; 2 metre!) gap between coaches or wagons, or locomotives and tenders, and we can easily explain away the slightly shorter physical length. Hell, I don't even mind the Heljan "Tubby Duff"; in fact, I like it very much. The extra width does show from some angles but overall it still looks like what it is supposed to represent, a class 47 Brush type 4!


And I fully agree with you SRman( Jeff)
 

·
Registered
Joined
·
8 Posts
Discussion Starter · #14 ·
Well folks, thanks for all the feedback. I have now completed the prototype with a lot more features than I originally intended for the first release, but hey while I was on a roll who cares.

For now I have posted the online version here: http://www.coalvillemodels.co.uk.

When I am satisfied no major flaws exist I will compile a windows desktop version for you to download and keep forever.

You can give me feedback here or via the website.

Thanks again for all your input.
 

·
Registered
Joined
·
999 Posts
Nice interface, but it still leaves the user with having to write down all the answers.

Without a hard copy of both the input and the output, the user cannot eyeball the results for gross input or transpositional errors when they take the results and record them on whatever they're using to record the answers.

I'm afraid that I'll be sticking to a spreadsheet.

You got me thinkijng and just out of curiousity to see how long it would take I knocked one up this morning in less than an hour which covers Gauges G, 1, O, OO, HO, TT, N (UK), N (True 2mm), N (Continental & US), Z, znd T. Additional Gauges (or more correctly scales) can be added at will up to a maximim of 29 in total (that's the limit in MS Excel for the formulae that I'm using). The Gauge is selected with a radio button and I can enter the prototype data as either Imparial or Metric or any combination. Its capacity is limited only by the number of rows in a spreadsheet, but I've currently only allowed for 250 rows of data, and being a spreadsheet the results can be saved and printed out for reference whilst model building

I can also change the scaling ratios if I need to which I've initially set up as:
Gauge G 1:22.5
Gauge 1 1:32
O Gauge (7mm:1ft) 1:43.54
OO Gauge (4mm:1ft 1:76.2
HO Gauge (3.5mm:1ft) 1:87.09
TT Gauge (3mm:1ft) 1:101.6
N (UK) Gauge 1:148
N (True 2mm:1Ft) Gauge 1: 152.4
N (Continental & US) Gauge 1:160
Z Gauge 1:220
T Gauge 1:450

All a bit OTT as I'm an OO man myself, but I was curious as to how long it would take me. If anyone wants a copy, let me know and I'll send it to you for free. It is macro free in case you're worried about macro viruses, but does use radio buttons to select the "Gauge". I do need to clear it down after use.

Sorry if I've ruined your marketing strategy, MidlandModeller, but I'm sure others will find your calculator useful for one-offs.

Keith.
 

·
Registered
Joined
·
8 Posts
Discussion Starter · #16 ·
No need to apologise Keith, (I don't have a marketing strategy as such, nothing to market except the free calculator anyway, but I guess that's a good enough reason to try.)

your spreadsheet sounds fantastic. In fact, can I have a copy? I will PM you with my details.

I like the idea of being able to save and print out the results, I may have a look at that as an option for a future update. Good thinking.

Meanwhile, I aim to have the desktop version available next week after some testing.

Thanks again for your input.
 

·
Registered
Joined
·
228 Posts
QUOTE (midlandmodeller @ 2 Jan 2009, 12:35) <{POST_SNAPBACK}>How do you deal with this? Do you think it matters? Do you use 13mm or 4mm? Or do you divide by 76?

Am I being too picky? Ordinarily I would probably use either and not worry too much about being a couple of mm out over a longer distance, but since I am now putting together a program to make calculating quicker, it suddenly seems to matter since it will give me a result to several decimal places.

Hi midlandmodeller. Thanks for offering your work for free.

I agree with SRman's point -- the odd mm on a rake of 00 coaches won't be noticed, especially considering how well we cope with a gauge in 00 that's 7" out of whack! However, I think something like this would be dead useful working in P4 or EM, where extra attention to detail is worthwhile.

Cheers,

Tom
 

·
Registered
Joined
·
8 Posts
Discussion Starter · #18 ·
Once again thanks for your input on my scale calculator project. The desktop version is now available as a free download from:

http://www.coalvillemodels.co.uk

Any problems, let me know, otherwise I hope you find it useful.

I am currently working on a version that allows you to save the results of your calculations for future reference. Very close now, but not enough free time so it will be a couple of weeks. For now I hope you enjoy using the current version on the link above.

Thanks again.
 

·
Premium Member
Joined
·
6,323 Posts
QUOTE (midlandmodeller @ 7 Jan 2009, 22:58) <{POST_SNAPBACK}>Once again thanks for your input on my scale calculator project. The desktop version is now available as a free download from:

http://www.coalvillemodels.co.uk

Any problems, let me know, otherwise I hope you find it useful.

I am currently working on a version that allows you to save the results of your calculations for future reference. Very close now, but not enough free time so it will be a couple of weeks. For now I hope you enjoy using the current version on the link above.

Thanks again.

An interesting old thread....wonder how he got on.......................
 
1 - 20 of 60 Posts
Top