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Protofour or P4 is a set of standards for
model railways allowing construction of models to a scale of 4 mm to 1 foot (1:76.2),
the predominant scale of model railways of the British prototype. For historical reasons almost all manufacturers of British prototype models use
00 gauge
OO gauge or OO scale (also, 00 gauge and 00 scale) is the most popular standard-gauge model railway standard in the United Kingdom, outside of which it is virtually unknown. OO gauge is one of several 4 mm-scale standards (4 mm to 1 foot, ...
(1:76.2 models running on gauge track). There are several
finescale standard
Finescale standards or Fine Standards are model railway standards that aim to be close to the prototype dimensions. Reduction in toylike, overscale flanges, pointwork, etc. In Britain it is particularly used because small British prototypes meant ...
s which have been developed to enable more accurate models than
00, and P4 is the most accurate in common use.
The P4 standards specify a scale model track gauge of for
standard gauge
A standard-gauge railway is a railway with a track gauge of . The standard gauge is also called Stephenson gauge (after George Stephenson), International gauge, UIC gauge, uniform gauge, normal gauge and European gauge in Europe, and SGR in E ...
railways. Joe Brook Smith was the first to propose use of an exact scale track gauge in July 1964, when also the term “Protofour” was invented by Malcolm Cross.
The standards were later published in Model Railway News by the Model Railway Study Group in August 1966.
Just as in the prototype railway, on a model the
wheel-rail interface is the fundamental aspect of reliable operation. So as well as a track gauge, P4 also specifies the wheel profile and track parameters to use, which are largely a scaled-down version of real-life standards with some allowances for practical manufacturing tolerances.
P4 standards have been extended to several other prototypes. Broader than standard gauges have been modelled using P4 standards, including
Brunel's gauge, modelled with track
and Irish P4, the
Irish broad gauge modelled in P4 in 4 mm scale with gauge track.
/ref> Several successful models of narrow gauge prototypes with a correspondingly accurate track gauges have also been produced to P4 standards.
P4 standards are promoted worldwide by the Scalefour Society, which is based in the United Kingdom. The EM Gauge Society also provides support for modelling to P4 standards: many P4 modellers belong to both societies. The standards document is hosted by the Scalefour Society
S4 Standard
The S4 Standard is maintained as part of the P4 standards.
See also
* OO gauge
* EM gauge
* Finescale Standards
* Rail transport modelling scales
External links
Scalefour Society, supporting modelling to P4 standards
EM Gauge Society, supporting modelling to both EM and P4 standards
CLAG - a group of finescale modellers based around London, England interested in building visually accurate working scale models in 4 mm scale gauge
References
{{Scale models
4 mm scale
Model railroad scales
Scale model scales