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Model Scales and Proportions

Most model makers have a good sense of scale and proportion, as evidenced by the models they make. Despite that, some I have talked with don't seem acquainted with common model scales and their uses.

Modern computers and copy machines can facilitate the sizing of drawings in an infinite variation of scales. One can literally size a model to suit oneself. Nevertheless, an under­standing of scales can be helpful. Drawings and purchasable models and components are available in specific scales as list­ed in the accompanying table.

You've probably used a mileage scale on a road map. The same principle applies to ship drawings. Good, recent drawings should have a graphic scale similar to the miles/kilometers scale on a map or should state the scale used to prepare the drawing-visually in the range of 1/32" = l' to 1/4" = l' (column 3 in the table).

Catalogs or lists of models, fittings, and drawings state their scales. Some firms even supply reduced-size copies of their drawings. They can however, be difficult to read or deci­pher as the lettering and lines grow thinner with each reduc­tion; it's wise to retain readable copies.

Office supply stores and department stores sell triangular or flat architectural or civil engineering rules for measuring and preparing scale drawings. The triangular architect rules include the seven scales noted in the table, plus 3/4", I", 1-1/2", and 2" or 3" = 1', depending on the age of the rule. The flat scales usually have eight scales: 1/8", 1/4", 1/2", I", 3/8", 3/4", 1-1/2", and 3" = 1'. Civil engineering rules are in multiples of 10: 10, 20, 30, 40, 50, and 60 divisions to the inch. Mechanical engineer's scales also exist and are used for drawings that are 1/8, 1/4, and 1/2.

Column 1 of the table lists the ratio of the model or draw­ing to the actual item. It's best to consider this as a fraction, e.g. 1:2400 = 1/2400, the model or drawing thus being reduced 1/2400th of the original. Scale feet per inch is obtained by dividing the denominator or second number of the ratio by 12. However, several of the model railroad scales are metric-­based and do not equate to reasonable fractions of an inch.

Some models are so crowded with details that an error of scale in locating or sizing an item can quickly cause problems. There are also limitations as to physically making some items to scale as they become too difficult to withstand handling. So, fidelity to scale is not always practical, although a general adherence to scale makes a model more accurate.

Some people have a special regard for models that are made "from scratch"-not utilizing any purchased fittings. If a model is built to an unusual scale-not listed in the table-you can reasonably conclude the model was truly scratch-built.

Our cousins outside the USA and UK will likely find the following table amusing as the metric system greatly simpli­fies their scales.

Common Model and Drawing Scales

Scale Ratio

Proportion
  Scale 

 
 One Scale Foot
 
Model to-
 
  Feet in

 
 Fraction of Decimal- Milligrams
Actual Size RR* One Inch AIE**   An Inch
Inch
Meters
1:2400   
 
   200
 
     1/200
  0.0050
  0.127
1:1250 
   
   104.2
 
     -
  0.0096
  0.244
1:1200
 
   100
 
     1/100
  0.0100
  0.254
1:768
 
   64
 
     1/64
  0.0156
  0.396
1:600
 
   50
 
     1/50
  0.0200
  0.508
1:384
 
   32
 
     1/32
  0.0313
  0.795
1:256
 
   21.3
 
     3/64
  0.0469
  1.191
1:220
  Z
   18.3
 
     -
  0.0546
  1.380
1:192
 
   16
    A
     1/16
  0.0625
  1.588
1:160
  N
   13.3
 
     -
  0.0752
  1.910
1:128
 
   10.7
    A
     3/32
  0.0938
  2.383
1:120
  TT
   10
    E
     1/10
  0.1000
  2.540
1:96
 
   8
    A
     1/8
  0.125
  3.175
1:87.1
  HO
   7.26
 
      -
  0.1377
  3.500
1:76.2
  00
   6.35
 
      -
  0.1575
  4.000
1:64
  S
   5.33
    A
      3/16
  0.1880
  4.775
1:48
  0
   4
    A
      1/4
  0.2500
  6.350
1:32
 
   2.67
    A
      3/8
  0.3750
  9.525
1:24
 
   2
    A
      1/2
0.5000
12.700

 *RR=Model Railroad Scale   **A/EA=Architect's, E=Civil Engineer's Scale 

Originally published in 70 Ships in Scale * Volume XI, Number 5