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CHARTS & TABLES
FOR ALMOST EVERYTHING
...IN ALL POPULAR SCALES

SCALE DIMENSIONS  -  SCALE SPEED
CAR WEIGHT  -  GRADES  -  DRAWINGS


Ever gotten confused converting prototype dimensions to your scale?
Just how fast does your loco really run with the throttle wide open?
How much should that 40' HO boxcar weigh? What if it's N-scale?
Does computing a 2½% grade leave you feeling weak?
Want to convert that HO-scale drawing to an N-scale drawing?

These are common questions and issues among us model RR types. To provide you with a quick and semi-comprehensive reference, here are five tables:

  1. Table 1 converts prototype dimensions into scale dimensions for all popular scales.

  2. Table 2 shows scale speed. Nearly all of us tend to run our trains too fast. To measure yours, mark off a 2 to 6 foot length of straight, flat track, and time your train thru this "trap;" divide the trap length in inches by the time in seconds; then find the closest match in the column for your scale. For example: if you mark a 40" trap, and your N-scale train covers the distance in 9 seconds, that's 40/9 = 4.44 inches/second; from Table 2, in the N-scale column, that's exactly 40 miles/hour.

  3. Table 3 shows the NMRA-recommended weight for rolling stock. For each scale, there's an "initial weight" plus an "additional weight" for each actual inch of car length (NOT scale length, but the length you actually measure on your little ruler/scale). Properly weighted cars look better, run smoother, and derail much less often. You'll need an reasonably accurate scale to do this right; I use a 16 ounce kitchen scale (from the local kitchen shop); if you're in O-scale, you may want a 32 ounce scale -- otherwise, 16 ounce is ideal. I use both ¼ ounce stick-on lead weights (from the Train Store), and thin lead sheets (from the plumbing supply store) to get the exact weight; just remember to attach 'em well so they don't slip around. I use cyanoacrylate (CA).

  4. Table 4 gives you grade percentage; the "rise" vs. the "run" for grades from 0.5% thru 5.0%. Remember that grade is scale-independent. Also, keep in mind that a 100% grade is equal to a 45° angle. Grade is the "rise" (how much the track rises vertically) divided by the "run" (the horizontal distance over which the rise occurs); hence, if the track rises ½" in 36" (that's 3 feet, but we gotta' use the same dimensions for both numbers), the grade would be 0.5/36 = 0.01389, or 1.4% (remember to multiply the decimal grade by 100 to get the percentage grade.

  5. Table 5 shows copier settings for resizing the scale of a drawing. Using you local Office Depot copier, you can easily convert a drawing rendered in any scale to a drawing in (almost) any other scale. A step-by-step procedure is outlined for drawings requiring multiple enlargements or reductions.

There are lots of other useful charts out there on the web. I'll provide links to them as I discover new ones. If you know of a useful chart, please let me know.

Drill Bit Size Chart
Table 1. Scale Dimensions
Prototype         Scale Dimension            
Dimension Z   N   TT   HO   S   O   G    
                                   
1 " 0.0045 " 0.0063 " 0.0083 " 0.0115 " 0.0156 " 0.021 " 0.044 "
3 " 0.0136 " 0.0188 " 0.0250 " 0.0344 " 0.0469 " 0.063 " 0.133 "
6 " 0.0273 " 0.0375 " 0.0500 " 0.0689 " 0.0938 " 0.125 " 0.267 "
12 " 0.0545 " 0.0750 " 0.1000 " 0.1378 " 0.1875 " 0.250 " 0.533 "
2 '   0.1091 " 0.1500 " 0.2000 " 0.2755 " 0.3750 " 0.500 " 1.067 "
5 '   0.2727 " 0.3750 " 0.5000 " 0.6889 " 0.9375 " 1.250 " 2.667 "
10 '   0.5455 " 0.7500 " 1.0000 " 1.3777 " 1.8750 " 2.500 " 5.333 "
20 '   1.0909 " 1.5000 " 2.0000 " 2.7555 " 3.7500 " 5.000 " 10.667 "
22.5 '   1.2273 " 1.6875 " 2.2500 " 3.0999 " 4.2188 " 5.625 " 1.000 '  
48 '   2.6182 " 3.6000 " 4.8000 " 6.6131 " 9.0000 " 1.000 ' 2.133 '  
50 '   2.7273 " 3.7500 " 5.0000 " 6.8886 " 9.3750 " 1.042 ' 2.222 '  
64 '   3.4909 " 4.8000 " 6.4000 " 8.8175 " 1.0000 ' 1.333 ' 2.844 '  
87.1 '   4.7509 " 6.5325 " 8.7100 " 1.0000 ' 1.3609 ' 1.815 ' 3.871 '  
100 '   5.4545 " 7.5000 " 10.0000 " 1.1481 ' 1.5625 ' 2.083 ' 4.444 '  
120 '   6.5455 " 9.0000 " 1.0000 ' 1.3777 ' 1.8750 ' 2.500 ' 5.333 '  
160 '   8.7273 " 1.0000 ' 1.333 ' 1.8370 ' 2.5000 ' 3.333 ' 7.111 '  
200 '   10.9091 " 1.2500 ' 1.667 ' 2.2962 ' 3.1250 ' 4.167 ' 8.889 '  
220 '   1.0000 ' 1.3750 ' 1.833 ' 2.5258 ' 3.4375 ' 4.583 ' 9.778 '  
1000 '   4.5455 ' 6.2500 ' 8.333 ' 11.4811 ' 15.6250 ' 20.833 ' 44.444 '  
5280 ' (1 mi) 24.000 ' 33.000 ' 44.000 ' 60.620 ' 82.500 ' 110.00 ' 234.67 '  
                                   
Scale   1:220   1:160   1:120   1:87.1   1:64   1:48   1:22.5    
Table 2. Scale Speeds
Prototype           Scale Speed        
Speed           (inches/sec)        
(miles/hour) Z   N   TT   HO   S   O   G
                               
1     0.08   0.11   0.15   0.20   0.28   0.37   0.78
2     0.16   0.22   0.29   0.40   0.55   0.73   1.56
5     0.40   0.55   0.73   1.01   1.38   1.83   3.91
10     0.80   1.10   1.47   2.02   2.75   3.67   7.82
15     1.20   1.65   2.20   3.03   4.13   5.50   11.7
20     1.60   2.20   2.93   4.04   5.50   7.33   15.6
25     2.00   2.75   3.67   5.05   6.88   9.17   19.6
30     2.40   3.30   4.40   6.06   8.25   11.0   23.5
35     2.80   3.85   5.13   7.07   9.63   12.8   27.4
40     3.20   4.40   5.87   8.08   11.0   14.7   31.3
45     3.60   4.95   6.60   9.09   12.4   16.5   35.2
50     4.00   5.50   7.33   10.1   13.8   18.3   39.1
55     4.40   6.05   8.07   11.1   15.1   20.2   43.0
60     4.80   6.60   8.80   12.1   16.5   22.0   46.9
70     5.60   7.70   10.3   14.1   19.3   25.7   54.8
80     6.40   8.80   11.7   16.2   22.0   29.3   62.6
90     7.20   9.90   13.2   18.2   24.8   33.0   70.4
100     8.00   11.0   14.7   20.2   27.5   36.7   78.2
110     8.80   12.1   16.1   22.2   30.3   40.3   86.0
120     9.60   13.2   17.6   24.2   33.0   44.0   93.9
150     12.0   16.5   22.0   30.3   41.3   55.0   117.3
Table 3. Car Weights
  Scale   Z   N   TT   HO   S   O   G
                                 
  Initial Weight (oz) *   0.5   0.75   1.0   2.0   5.0   *
    +                            
  Add'l Weight                          
  per Inch of *   0.15   0.375   0.50   0.75   1.00   *
  car length (oz)                          
                                 
  * Note: No standard exists for Z- or G-Scale            
                                 
  EXAMPLE                          
  A 40' boxcar in HO-scale would be 5.5" long; hence, the recommended total  
  weight would be W = 1.0 + (5.5 x 0.5) = 3.75 ounces.            
Table 4. Grades
Prototype     Vertical Rise for a Horizontal Run of        
Grade 12"   24"   36"   48"   60"   72"   96"    
                                   
0.5   % 0.06 " 0.12 " 0.18 " 0.24 " 0.30 " 0.36 " 0.48 "  
1   % 0.12 " 0.24 " 0.36 " 0.48 " 0.60 " 0.72 " 0.96 "  
1.5   % 0.18 " 0.36 " 0.54 " 0.72 " 0.90 " 1.08 " 1.44 "  
2   % 0.24 " 0.48 " 0.72 " 0.96 " 1.20 " 1.44 " 1.92 "  
2.5   % 0.30 " 0.60 " 0.90 " 1.20 " 1.50 " 1.80 " 2.40 "  
3   % 0.36 " 0.72 " 1.08 " 1.44 " 1.80 " 2.16 " 2.88 "  
3.5   % 0.42 " 0.84 " 1.26 " 1.68 " 2.10 " 2.52 " 3.36 "  
4   % 0.48 " 0.96 " 1.44 " 1.92 " 2.40 " 2.88 " 3.84 "  
4.5   % 0.54 " 1.08 " 1.62 " 2.16 " 2.70 " 3.24 " 4.32 "  
5   % 0.60 " 1.20 " 1.80 " 2.40 " 3.00 " 3.60 " 4.80 "  
Note: Example shown below is for the RED entry above.            

2% grade drawing

Table 5. Scale Conversions for Drawings
  Drawing     Copier Setting to Change Scale to…          
  Scale   Z   N   TT   HO   S   O   G  
                                   
  Z     100%   138%   183%   253%   344%   458%   978%  
                                   
  N     73%   100%   133%   184%   250%   333%   711%  
                                   
  TT     55%   75%   100%   138%   188%   250%   533%  
                                   
  HO     40%   54%   73%   100%   136%   181%   387%  
                                   
  S     29%   40%   53%   73%   100%   133%   284%  
                                   
  O     22%   30%   40%   55%   75%   100%   213%  
                                   
  G     10%   14%   19%   26%   35%   47%   100%  
                                   
Note: When attempting to enlarge a drawing beyond a copier's range, you'll need to
do it in several steps. The chart below shows the two sucessive enlargements
required for copies greater than 200%. For example: to get a 333% copy,
first you make a 200% copy; then, using that 200% copy as your master,
make a 166% copy; the result will be a 333% copy of the original drawing.
Similarly, when making a copy less than 20% of the original, I suggest also
doing it in two steps. For example, if you want to make a 14% copy: first,
make a 50% copy; then, using that 50% copy as your master, make a 28%
copy; the result will be 14% copy of the original drawing.
  Drawing     Copier % Settings to Change Scale to…      
  Scale   Z   N   TT   HO   S   O   G  
                                   
  Z     100%   138%   183%   200+126   200+172   (1)   (2)  
                                   
  N     73%   100%   133%   184%   200+125   200+166   (3)  
                                   
  TT     55%   75%   100%   138%   188%   200+125   (4)  
                                   
  HO     40%   54%   73%   100%   136%   181%   200+193  
                                   
  S     29%   40%   53%   73%   100%   133%   200+142  
                                   
  O     22%   30%   40%   55%   75%   100%   200+106  
                                   
  G     50+20   50+28   50+38   26%   35%   47%   100%  
                                   
  Notes:   (1) 3-step enlargement process: 200%, then 200%, then 114%.      
      (2) 4-step enlargement process: 200%, then 200%, then 200%, then 122%
        (I really don't recommend a 4-step process…but you could try.)  
      (3) 3-step enlargement process: 200%, then 200%, then 178%.      
      (4) 3-step enlargement process: 200%, then 200%, then 133%.      
                                   

Finally...if you'd like a printout of one or more of the above tables on a sheet of paper all by itself, just click on the table you want below:

Table 1. Scale Dimensions
Table 2. Scale Speeds
Table 3. Car Weights
Table 4. Grades
Table 5. Scale Conversions for Drawings


Didn't find the info you needed? Have an insatiable thirst for knowledge? You might want to visit Rick Blanchard's Web Site. He has even more reference tables.


That's about it. If you have questions, just Email me and I'll do my best to answer them. If there are any glaring omissions from the tables, please let me know.


Thanks for visiting!

Revised 6-25-07