P4 gauge
Encyclopedia
P4 or Protofour is a set of standards (of which the article name "P4 gauge" is a misnomer as the standards concern much more than simply the gauge of the track) for model railways allowing a more accurate 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 the inaccurate 00 gauge (1:76.2 models running on under-scale gauge track). P4 represents the most significant development of a movement that started in the 1950s to model accurately to the 4mm to 1 foot scale.
The P4 standards specify a scale model track gauge of for standard gauge
railways. The late Joe Brook Smith was the first to 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, and Irish P4, the Irish broad gauge
modelled in P4 in 4mm scale with gauge track. 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 can be downloaded from http://scalefour.org/downloads/P4-standards.pdf and also viewed at http://www.clag.org.uk/p4standards.html
The P4 standards include options with reduced tolerances and an increased back-to-back measurement that are an exact scaling down of prototype dimensions, and which are referred to as S4 standards. These are chosen by railway modellers who wish to avoid the minor compromises designed into P4 standards.
The P4 standards specify a scale model track gauge of for standard gauge
Standard gauge
The standard gauge is a widely-used track gauge . Approximately 60% of the world's existing railway lines are built to this gauge...
railways. The late Joe Brook Smith was the first to 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, and Irish P4, the Irish broad gauge
Irish gauge
Irish gauge railways use a track gauge of . It is used in* Ireland * Australia where it is also known as Victorian Broad Gauge* Brazil where it is also known as Bitola larga no Brasil....
modelled in P4 in 4mm scale with gauge track. 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 can be downloaded from http://scalefour.org/downloads/P4-standards.pdf and also viewed at http://www.clag.org.uk/p4standards.html
The P4 standards include options with reduced tolerances and an increased back-to-back measurement that are an exact scaling down of prototype dimensions, and which are referred to as S4 standards. These are chosen by railway modellers who wish to avoid the minor compromises designed into P4 standards.
External links
- Scalefour Society, supporting modelling to P4 and S4 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 4mm scale gauge
- http://website.lineone.net/%7Esjohnson40/