What is the actual "six foot" spacing between double track lines, and
is it measured between the inner faces of each track i.e. at the wheel
flange point, or the outer edge of each track?
I'm sure I had a proper drawing of this somewhere, but can't put my
hands on it at the mo... :-(
I have an idea that in such as N scale, this is increased a bit - if
so, by how much?
Actually, track spacing is measured centre to centre; see excerpt from
For model railways, the spacing has to be wide enough to prevent passing
trains from sideswiping each other. Space the tracks for the longest
rolling stock. In N it should be 1" or more centre to centre. You can
make a gauge for rail-to-rail spacing by laying down a couple of pieces
of track to the desired spacing, and cutting slots in a piece of 2mm
plastic to accommodate the inner rails. You may as well make one for
straight track and one (or more) for curved track. You can make four
gauges on piece of plastic, after all.
If you want prototypical accuracy, keep in mind that track spacing
varies by prototype, era, type of line, traffic, etc. IOW, if it looks
right, it is right.
Excerpt from Wiki article:
The distance between the track centres makes a difference in cost and
performance of a double track line. The track centres can be as narrow
and as cheap as possible, but maintenance must be done on the side.
Signals for bi-directional working cannot be mounted between the tracks
so must be mounted on the 'wrong' side of the line or on expensive
signal bridges. Very narrow track centres are also undesirable for high
speeds, as pressure waves knock each other as high speed trains pass.
Narrow track centres might be 4 m or less. Narrow track centres may have
to be widened on sharp curves to allow for long rail vehicles following
the arc of the curve, and this increases a surveyor's workload. Widening
a track centre to 5 m or so suits high speed trains passing each other,
and eliminates the need to widen the centres on sharp curves. Increasing
width of track centres of 6 m or more makes it much easier to mount
signals and overhead wiring structures.
Very wide centres at major bridges can have military value. It also
makes it harder for rogue ships and barges knocking out both bridges in
the same accident.
But not when referring to "the 6 foot" which is measured rail to rail.
Whether it's inner or outer face of the rail is largely immaterial, an
inch or two in seventy-two.
The "6 foot" varied so shouldn't be taken as an absolute.
How much you need to increrase the spacing of model track (any gauge
or scale) depends on how tight your curves are.
The two relevant dimensions are "the four foot way" and the "six foot way".
The first is the gauge, which shows how wooley both those terms are.
Add the two together as they stand and you'd get a ten foot center to
dimension between tracks, which would barely be workable. I'm sure the
originated back in the early years of railways when locomotives and rolling
stock were smaller and track spacing would have widened since.
The minimum spacing would allow two trains to pass with a man standing
between the tracks.
Of course once prototype double track has been laid and bridges, platforms,
crossovers etc laid it would take an awful lot of work and materials to
relay them at a wider spacing,. With that in mind, the spacing on any given
piece of track is probably as laid in pre-grouping era. 12 or 13 feet would
probably be about right. Tracks laid for modern high speed trains would be
several feet wider.
On model curves the rolling stock swings at the outer corners and inside
center so tracks need wider spacing. The sharper the curves and the longer
the rolling stock, the further the swing will be so the wider the track
Generally steam locomotive models will extend further outside the curve
than Diseasals etc.
Nodel track spacing is a practical compromise that can't be avoided.
Narrowed gauge and increased spacing will always look wrong!
No - the six foot is exactly that. Standard double track spacing on
straights is 11' 2" : 4' 8.5" plus twice the rail thickness (nominal
2.75") plus six feet. Source: Ministry of Transport Requirements -
1950 edition. The only historic routes where there has been any
substantial increase on this are ex-broad gauge, where the spacing
between platforms opens out by an extra 4' 7".
You are right that modern high speed lines have a wider spacing.
Many thanks to all for their very helpful comments. It seems that
there's scope (and sometimes necessity!) for a measure (!) of
modeller's licence, especially on tight bends, but it's also nice to
know what the 'official' dimensions are.
As a matter of interest were things different on the GWR with the reduction
of guage from broad to standard. Did they use any of the extra space between
tracks or on one or both sides. Did they reduce the total width immediately
or over time ?
Then theres the Great Central, wasnt that different as it was built to
continental loading guage ?
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