Model Railway News

September 1966




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

A New Approach to Modelling Standards by
A Model Standards Study Group
Concluded from the August, Model Railway News
General Observations

It is clear from the Study Groupís 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 Associationís 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.

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.

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

414-1m.jpg (74941 bytes)
Above: Model coaching stock fitted with Protofour wheels. Triang bogies, fitted with new wheels without modification; coaches by Kitmaster.




Below: 15 ton private owner hopper wagon fitted with Protofour wheels
modified from Nucro originals.
414-2m.jpg (78947 bytes)

415-1s.gif (54113 bytes) 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.

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.í
Unsatisfactory owing to excessive flange width.

415-2m.jpg (66672 bytes)
Above: 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!

Below: All for 4mm. Scale, yet all different! These wheels are 16.5 mm.(top)
18.0 mm. (middle) and protofour 18.83 mm. (lower). Note that the distance
over wheel faces for the Protofour and EM wheels is the same, therefore no
restrictions on axleguard clearance obtain beyond those met in EM operations.
The wheels are resting on millimetre graph paper.
415-3m.jpg (73951 bytes)

Copyright - Model Railway Study Group, reproduced with permission.

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