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S-4.1 Wheels, Proto & Fine Scales

S-4.1 Wheels, Proto & Fine Scales

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The Proto:xx dimensions have traditionally been documented with Min and Max values instead of limits. This practice has been continued for S-3.1 and S-4.1.

Original S-4.1 approved 2004 had editing errors based on imporper display of hidden precision values and in the calculation of metric conversion values.

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S-4.1 PROTO Wheels

 

 K B N T D

 
Name of Scale Wheel Check Gage Back to Back Wheel Width Flange Width Flange Depth
Wheel Gage
(Note 5)

 

 

 

 

 Min Max Min Max Min Max Min Max Min Max Min Max

 

 

 

 

 

 

 

 

 

 

 

 
Proto:20.3 Inch 2.654 2.681 2.597 2.627 0.271 0.282 0.057 0.067 0.050 0.062 2.711 2.761
mm 67.41 68.10 65.96 66.73 6.88 7.16 1.45 1.70 1.27 1.57 68.86 70.13

 

 

 

 

 

 

 

 

 

 

 

 

 

 
Proto:20.3n3 Inch 1.645 1.672 1.588 1.618 0.271 0.282 0.057 0.067 0.050 0.062 1.702 1.752
mm 41.78 42.47 40.34 41.10 6.88 7.16 1.45 1.70 1.27 1.57 43.23 44.50

 

 

 

 

 

 

 

 

 

 

 

 

 

 
Proto:32 Inch 1.685 1.702 1.649 1.668 0.172 0.180 0.036 0.042 0.032 0.039 1.721 1.752
mm 42.80 43.23 41.88 42.37 4.37 4.57 0.91 1.07 0.81 0.99 43.71 44.50

 

 

 

 

 

 

 

 

 

 

 

 

 

 
Proto:32n3 Inch 1.045 1.062 1.009 1.027 0.172 0.180 0.036 0.042 0.032 0.039 1.081 1.111
mm 26.54 26.97 25.63 26.09 4.37 4.57 0.91 1.07 0.81 0.99 27.46 28.22

 

 

 

 

 

 

 

 

 

 

 

 

 

 
Proto:48 Inch 1.124 1.134 1.100 1.112 0.115 0.120 0.024 0.028 0.022 0.026 1.148 1.168
mm 28.55 28.80 27.94 28.24 2.92 3.05 0.61 0.71 0.56 0.66 29.16 29.67

 

 

 

 

 

 

 

 

 

 

 

 

 

 
Proto:48n3 Inch 0.697 0.707 0.673 0.685 0.115 0.120 0.024 0.028 0.022 0.026 0.721 0.741
mm 17.70 17.96 17.09 17.40 2.92 3.05 0.61 0.71 0.56 0.66 18.31 18.82

 

 

 

 

 

 

 

 

 

 

 

 

 

 
Proto:64 Inch 0.842 0.850 0.825 0.834 0.087 0.092 0.017 0.019 0.018 0.020 0.859 0.872
mm 21.39 21.59 20.96 21.18 2.21 2.34 0.43 0.48 0.46 0.51 21.82 22.15

 

 

 

 

 

 

 

 

 

 

 

 

 

 
Proto:64n3 Inch 0.522 0.529 0.505 0.514 0.087 0.092 0.017 0.019 0.018 0.020 0.539 0.552
mm 13.26 13.44 12.83 13.05 2.21 2.34 0.43 0.49 0.46 0.51 13.69 14.02

 

 

 

 

 

 

 

 

 

 

 

 

 

 
Proto:87 Inch 0.621 0.624 0.607 0.613 0.064 0.069 0.012 0.014 0.013 0.014 0.631 0.641
mm 15.77 15.85 15.42 15.57 1.63 1.75 0.30 0.36 0.33 0.36 16.03 16.28

 

 

 

 

 

 

 

 

 

 

 

 

 

 
Proto:87n3 Inch 0.383 0.388 0.371 0.378 0.064 0.069 0.012 0.014 0.013 0.014 0.395 0.406
mm 9.73 9.86 9.42 9.60 1.63 1.75 0.30 0.36 0.33 0.36 10.03 10.31

 

Fine Scale Options

 

 

Name of Scale

 K B N T D

 
Wheel Check Gage Back to Back Wheel Width Flange Width Flange Depth Wheel Gage
(Note 5)

 

 

 

 

 Max Min Min Max Max Max

 

 

 

 

 

 
Fine:HO Inch 0.613 0.581 0.086 0.025 0.023 0.638
mm 15.6 14.8 2.2 0.6 0.6 16.2

 

 

 

 

 

 

 

 
Fine:HOn3 Inch 0.377 0.345 0.086 0.025 0.023 0.402
mm 9.6 8.8 2.2 0.6 0.6 10.2

 

 

 

 

 

 

 

 
Fine:TT Inch 0.441 0.415 0.071 0.020 0.022 0.461
mm 11.2 10.5 1.8 0.5 0.6 11.7

 

 

 

 

 

 

 

 
Fine:TTn3 Inch 0.270 0.244 0.071 0.020 0.022 0.290
mm 6.9 6.2 1.8 0.5 0.6 7.4

 

 

 

 

 

 

 

 
Fine:N Inch 0.336 0.323 0.051 0.013 0.017 0.349
mm 8.5 8.2 1.3 0.3 0.4 8.9

 

 

 

 

 

 

 

 
Fine:Nn3 Inch 0.228 0.215 0.051 0.013 0.017 0.241
mm 5.8 5.5 1.3 0.3 0.4 0.3

NOTES:

  1. See Tech-Note TN-1.1.2 (Proto and Fine) for a more detail on the Proto Scale dimensions and issues related to building in Proto and Fine Scale.
  2. Options of Proto:Scale wheel profiles are provided in the Tech Note.
  3. Tread Taper is 1:20 for all profiles.
  4. Tread Taper and Filet Radius are not optional -- but are required for Proto:Scales.
  5. Wheel Gage is from facing flange gage point to facing flange gage point (K+T).