Reference to the lower of the two diagrams on my original email shows that the back to back distance for tram wheels is either 1380 or 1389 mm (difficult to read) while the back to back distance for railway wheels is 1360 (ignoring decimals). This means that the heavy rail wheel will not fit in the tramway groove. Note that in the diagram the left sets of wheels are hard up against the rail, while the wheels to the right have the heavy rail flange considerably in from the tram wheel flange.

This means that where you need to run heavy rail equipment on tram track, if you use grooved rail, you must use a narrower gauge, such as the 4' 7 3/4" used by Glasgow. I believe that Budapest also hauled heavy rail goods vehicles over the tramway track, but I think they did not use grooved rail on the relevant sections. Rather, probably, they used a check rail set to railway standards, leaving a very wide gap.

If you can find diagrams of rail sections used in the USA I believe that you will find that the groove is considerably wider than the UK standards. As near as I can make out from the diagram given for BS 8 and 8c rails in Dover (p 348) - yes, the text confirms, the width of groove on straight track was 1.125" (28.575 mm) but on curved track less than 150 ft radius it was 1.25" (31.75).

European grooves may well be wider, I have a diagram of NT1 and NT3 grooved rail made by Hutnik, (Moravia Steel) which has groove widths of 34.17 and 42.7 mm, for rail weights of 65.07 and 60.63 kg, respectively,

Regards

Dudley Horscroft
----- Original Message -----
From: Trevor Watson
To:TramsDownUnder@...
Sent: Thursday, March 21, 2013 9:35 AM
Subject: [TramsDownUnder] Re: Ballarat 6b/driving on worn rail

I think it's the other way around heavy rail just wont fit thru tramway points... I do recall that in Sydney trams were sometimes towed behind railway locomotives over railway track and in some cases for considerable distances i.e. Newcastle to Sydney.
I have a drawing somewhere and the important criterion is the "cone" machined onto the tyres. In "standard" situations its 3 degrees for both railway and tramway. The cone is the bit of the tyre that contacts the rail. Dimensionally there are considerable differences between the flanges.... Being a true tramus tragicus I have a sheet metal profile I carry with me and despite claims that Steam trams can't run on electric tram track I offered the template up to the tyres on 103A and guess what it fits exactly...

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