track centers

NW Mailing List nw-mailing-list at
Thu Aug 21 13:21:20 EDT 2014

Thanks Grant I do approve of your attention to detail


From: NW Mailing List 
Sent: Tuesday, August 19, 2014 6:54 PM
To: nw-mailing-list at 
Subject: Re: track centers

For track centers on curves:

TCc = TCt + (K / R)

should work for different scales and units of measure by scaling the term "K".

For all terms in millimeters: 

TT3 (1:101.6) scale, K = 4300 [corrected from previous post]

TT (1:120) scale, K = 3000

For all terms in inches:

N (1:160) scale, K = 3

TT (1:120) scale, K = 5

HO (1:87) scale, K = 9

S (1:64) scale, K = 17

O (1:48) scale, K = 30

A disclaimer. . .
I have only tested this empirically in HO scale. Your results may vary with scale and tolerances of wheel gauge, track gauge, track centers, and overhang.

Grant Carpenter
On 8/18/2014 1:22 AM, NW Mailing List wrote:

  Thanks Grant I am very grateful for your knowledge and help, incidentally although my British stuff is 3mm the American layout I want to do is actually the original American TT scale at 1:120 at 2.54 mm to the foot so do you know the formula for that one

  Thanks and regards

  On Aug 17, 2014, at 5:06 PM, "NW Mailing List" <nw-mailing-list at> wrote:

    Main track centers on tangent (TCt) were 13' apart, later 14' (post-war) and wider in curves. For track centers on curves (TCc) in British TT (3mm) scale, try TCc = TCt + (5000 / R), where R is the inside track radius (all terms in millimeters). 

    Grant Carpenter
    On 8/16/2014 9:32 AM, NW Mailing List wrote:

      Bit more help please chaps if anybody can oblige. What is the minimum distance between tack centers on mainline double track

      Thanks and regards

      Sent: Thursday, July 31, 2014 

      The standard tie spacing on centers was 19-1/2" for main, heavy branch, switching, and engine running tracks; 21-1/2" for light branch, switching, and engine running tracks, and heavy passing sidings and yard tracks; 23-3/4" for light passing sidings and yard tracks, and heavy industrial, shop, and storage tracks; 26-3/4" for light industrial, shop, and storage tracks; and 30-1/2" for station sidings, unimportant spurs, etc. (L-168, 1946)

      Standard ties measured 9"W x 7"H x 8-1/2'L (L apparently minimum, not nominal).

      Switch ties measured 9"W x 7"H and were cut in 6" intervals from 9' to 16'L . Headblock ties varied from about 11-1/2' to 14-1/2'L, depending on the machine.

      Bridge ties measured 10" x 10" x 10'L (or longer where needed) on 15" centers. (L-50, 1943)

      Grant Carpenter
      On 7/27/2014

        Hi folks
        Can somebody tell me the standard tie spacing on N&W  130lb rail please together with actual size of N&W rail ties. I am trying to do a small TT scale project with handlaid track and need sizes to get it right. I have ordered some drawings from the archives but I am too impatient to wait for them to arrive in the UK

        Thanks and regards

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