Gauge Widening & Flangeway widths

[Overseer]

While not necessarily directly related to UK practice I thought people might be interested in the following extract from a drawing titled "Trackwork Layouts - Limiting Angles - Flangeways & Curvatures". It is for 5'3" gauge but I would think the dimensions for standard gauge would be similar.


The dimensions for 7mm scale would be:
Radius - Gauge Widening - Flangeways
6 chains = 2772mm - 0.292mm - 1.314mm
7 chains = 3234mm - 0.220mm - 1.241mm
8 chains = 3696mm - 0.146mm - 1.167mm
10 chains = 4620mm - 0.073mm - 1.095mm
Over 10 chains - 0mm - 1.022mm

(The scale dimensions are based on 7mm to a foot for the radius and 1:43.5 for the widening and flangeway dimensions, which are not quite the same but will do for comparison purposes)

The drawing doesn't specify the radius at which check rails are required, probably because that is also dependant on the use of the track. The gauge widening is quite significant even at 6 chains (about 9' in 7mm scale). It would be interesting to check the amount of gauge widening the S7 Group three point gauge produces at various radii. Is the equivalent information available for BR or the constituent railways?

This information is not just for Scale7 but it is less relevant to finescale where the tolerances are more lax.

 

[Simon Dunkley]

Is the equivalent information available for BR or the constituent railways?

This information is not just for Scale7 but it is less relevant to finescale where the tolerances are more lax.

Yes, it is available, and has been published on the web and freely available for some years, derived from the first edition of British Track:
SSMRS Standards

To save the difficulty of calculation, here are the figures converted back to prototype:

Radius: Gauge Widening and flangeway widening:
Straight down to 10 chains none
10 chains down to 7 chains + 1/4"
7 chains down to 5.5 chains + 1/2"
Below 5.5 chains + 3/4"

I may be guilty of rounding by a few feet (like 4!), to keep things simple. Note that the flangeway widening would happen to flangeways on both rails, reducing the "span" over the rubbing faces by the amount of gauge widening.

In S, a chain works out as a little over 1', which is handy, but here is a table of chains to feet for a few scales:

Scale: Chain:
1:32 2' 0.75" (2' and 3/4")
1:43.54 1' 6.016" (1' and 6. 1/64")
1:64 1' 0.375" (1' and 3/8")
1:76.2 10.394" (10 and 9/64")
1:101.6 7.795" (7 and 51/64")
1:148.4 5.197" (5 and 9/132")

If you don't work in ratios, then these are for G1 (done properly), 7mm scale, S, 4mm scale, 3mm scale and 2mm scale.
They are also a good indication of why one shouldn't mix measurements.