Model Railway News

September 1966

PROTOFOUR

A New Approach to Modelling Standards by A Model Standards Study Group

Comprising:
J.S. Brook Smith
D.E. Jones
M.S. Cross
W.L. Kidston
B. Morgan
Dr. B. Weller

Concluded from Part 1/2: Model Railway News, August 1966

General Observations

Model coaching stock fitted with Protofour wheels. Triang bogies, fitted with new wheels without modification; coaches by Kitmaster.

It is clear from the Study Group's investigations that the BRMSB standards lack the basic dimensions to ensure complete reliability, i.e., standard wheel and rail contours designed to work together. Secondly the BRMSB dimensions can be shown to be critical in certain situations, and in the case of TT3, clearly defective. Under these circumstances, the Model Engineering Trade Association's task is indeed a thankless one.

The Protofour Standards, by adopting prototype practice, have eliminated these basic weaknesses and at the same time offer a balanced structure of dimensions and a truly prototypical appearance in the finished model.

15 ton private owner hopper wagon fitted with Protofour wheels 
	    modified from Nucro originals.

15 ton private owner hopper wagon fitted with Protofour wheels modified from Nucro originals.

For those who have no interest in accurate representation of the prototype, the BRMSB systems offer a range of components with which a working model may be assembled. On the other hand, those who are prepared to adopt minimal springing in the vehicles and to attempt to lay reasonably level track, can now produce a reliable and correctly scaled model railway with a completely authentic appearance.

With BB spacing plus twice the tyre width, it can be seen that the clearances between axleguards are almost the same as EM Gauge. This feature, combined with gauge widening, means that there are no greater restrictions on minimum radius curves than in the present EM Gauge.

The many technical advances on the present systems, and the correct appearance of the models, give reason to believe that Protofour might become the accepted scale railway modelling standard of the future.

Wheel diagramIn the diagram, four model wheel contours are compared to each other, and to a British Railways wheel drawn to the same comparative scale.

The diagram shows the variations in flange contours between model wheels in the same general category, and the variation in wheel clearances between standards.

The wheels are shown with a common datum, i.e., the wheel back. It is assumed that in all cases the opposite wheel back is in contact with the check rail; the running rails are thus positioned in accordance with the published standards. As the BRMSB wheel has an effective flange greater than the nominal figure, (approximately 0.8 mm. versus 0.5 mm.) the interference at the nose of the crossing can be seen as a shaded area.

A curiosity of the BRMSB standards for "00" Gauge is the discrepancy between the published check gauge and the distance over checks + flangeway, which should be identical, but in fact differ by 0.25 mm.

Model of Midland ventilated van on the Protofour tracks.

Midland ventilated van on the Protofour tracks. Apart from correctly proportioned wheels, the scale coupling links help in creating an atmosphere of authenticity. The next paintshop visit will obliterate the lower left hand number!

Summary of Wheel and Gauge combinations

1. Manchester/EM Gauge

Unrestricted. Tyre width 2.00mm., minimum.

2. BRMSB/EM Gauge

Possible interference at the crossing nose. Tyre width 2.00mm minimum.

3. BRMSB/00 Gauge

With stated check gauge of 15.30mm., similar interference to EM Gauge. With check gauge 15.25mm. (distance over checks + one flangeway) operation satisfactory. Tyre width 2.50mm., minimum.

4. RP 25, or NEM/H0 Gauge

Unrestricted. Tyre width 2.70mm., minimum.

5. RP 25, or NEM/BRMSB 00 Gauge

May be used if wheels are set to H0 BB gauge of 14.4mm. and track check gauge is standardised at 15.25mm. See (3) above. Tyre width 2.50mm., minimum.

6. RP 25, or NEM/EM Gauge

Unsatisfactory owing to excessive flange width.

Copyright - Model Railway Study Group, reproduced with permission.