Standard Gauge on Tramways, Then & Now.

[melmerby]

Hi all

 

With first generation UK tramways, Standard Gauge was usually quoted as being 4' 8½".

However if a Standard Gauge tramway needed to accomodate railway wagons such as on Glasgow Tramway, the gauge was actuallly 4' 7¾" and the standard gauge wagons ran on their flanges in the tram track flangeways.

 

Clearly there was a difference between Tramway Standard gauge vehicles and Heavy Rail Standard gauge vehicles. I assume it was to do with the wheel profiles.

So what has changed between then & now where Standard Gauge trams now seem to be compatible with heavy rail vehicles? (e.g. Sheffield)

[Mol_PMB]

The Sheffield tram-trains and Manchester trams both have a special wheel profile (similar, though not quite identical to each other). Both have sections of running over Network Rail infrastructure.

 

The flange tip is thin, to fit in the grooved rail. But the flangeback is stepped out just above rail height, to give the 1360mm back-to-back suitable for main line running.

On the sections with 'main line' type infrastructure, the checkrails are raised above rail height to contact the step in the flangeback.

(Raised checkrails are common practice on Network Rail these days anyway, and one of the reasons 9Fs are banned, but that's another story...)

[Jeremy Cumberland]

The old standard flangeway on straight track was 1⅛" (flangeways were wider on sharp curves). With a track gauge of 4' 8½", this would result in a distance between flangeways of 4' 6¼", which is more than the then-standard back-to-back distance of between 4' 5⅝" and 4' 5⅞", depending on the wheel profile.

 

Reducing the gauge to 4' 7¾" reduces the distance between flangeways to 4' 5½", which is less than the wheelset back to back.