Another track centers question

[NW Modeling List]

In inches, for 1.5" (1:8) scale, K = 1000

For Z scale, K is the same as in N scale, as any difference gets lost in 
rounding error.

K only varies with scale, so any (narrow) gauge of the same scale would 
have the same value of K. The reverse is true for G; it has several 
scales for one gauge. For some context, this formula was derived from 
the prototype for determining main line track centers on curves, 
allowing for smokebox overhang. Other factors affecting centers may 
apply in G gauge and narrow gauge, and for tracks other than main line 
in any scale. For example, yard track centers might vary to allow more 
room for carmen. Ladder tracks, particularly parallel ladders, need 
wider spacing, but this too is driven by smokebox overhang on curves (in 
turnouts).

Grant Carpenter
---
On 8/22/2014 9:11 AM, NW Mailing List wrote:
> What about Z and G and 1.5"?  And, as I thought about G and the fact that several different scales use G track, I wonder should HOn3 and On3 use  N and HO or HO and O formula?  Just asking.
>
> I have such a bad case of train nutisim that I have models in all of the scales mentioned except HO narrow gauge.  I seriously was hoping for a Z calculation, as I am just starting a layout in that scale.  I have to use a magnifier to work on it, but I'm giving it a shot.
>
> And, since I brought up multiple scales; I have a display I take to shows which has several N&W boxcars with half moon herald. One each in Z, N, HO, S, O, and G.  If anyone has any knowledge on whether or not there was ever one in TT I would appreciate the information.
>
> Bob Huston
>
>
> ---- NW Mailing List<nw-mailing-list at nwhs.org>  wrote:
>> Thanks Grant I do approve of your attention to detail
>>
>> regards
>> Richard
>>
>> From: NW Mailing List
>> Sent: Tuesday, August 19, 2014 6:54 PM
>> To:nw-mailing-list at nwhs.org  
>> 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
>> ---
>>      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).
>>