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 Post subject: Transitions and cant.
PostPosted: Sat May 07, 2011 1:22 am 

Joined: Mon Feb 08, 2010 3:08 am
Posts: 15
Having just begun to get back into extending my 4mm layout the subject of curve transitions and associated cant(superelevation) has come up.
I tried to find out when these two first became used . Does anyone know? What has been their history on the LNWR ?

John Brouwer

PostPosted: Sat May 07, 2011 11:05 am 

Joined: Sun Feb 07, 2010 9:29 am
Posts: 126
The attached images are taken from an LNWR PW Ganger's Notebook c1920 in the Society Archives. The notebook is full of rules of thumb for laying out and checking trackwork.

It is not easy to interpret but I think that the table (TRACK007(8)) gives various lengths of string to be stretched across the running rail as in diagram (TRACK007(7)) for the relevant line speed. The distance from the middle of the string to the rail averagae (rail centreline?) in inches gives the cant in inches. TRACK007(08) gives the rate of change of cant and maximum cant.

Later a couple of examples are given: 50 chain radius at High speed 3in superelevation, 50 chain radius at low speed 1.5in superelevation.

I cannot find anything on transition curves in the notebook.

Hope the above is of some help.


Dave Pennington

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PostPosted: Thu Dec 01, 2011 12:23 pm 

Joined: Wed Feb 10, 2010 5:00 pm
Posts: 23
Location: York
In 1922, Transition Curves were very much in their infancy. A Paper was read to the Institution of Civil Engineers in January 1909, by Mr W H Shortt, on realigning curves by the adjustment of versines. This would allow the cant to match the changing radius of the curve. When the Streamlined Trains were being run in the 1930's, jolts were apparently felt going into and out of curves. But on large radius curves, these were not too bad - it was on sharp curves that the greatest jolts are felt. Versines and Transition Curves only came into general use after the Second World War.

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