Dave W

For Network Rail normal min contact wire height is 4.165m with a max of 5.94m however these are standard limit values which apply after tolerances and other track and OLE parameters have been considered in the design. I would suggest for a model that the contact wire height should be within the scale equivalent of about 4.3m and 5.8m. The nominal height is 4.7m and is the height at the supporting structures that would apply when there were no features such as bridges or level crossings. The normal contact wire height at level crossings is 5.8m. Where the contact wire height needs to be changed the gradient of the wire is normally upto a maximum of 1 in 5 x the line speed. Eg. A line speed of 100mph would normally have a contact wire gradient of 1 in 500 or shallower. In model terms I would make the gradient a lot steeper than this due to the compression of length that the majority of us model to. The above is a rough guide based on current practice. There are always exceptions to the norm on the real railway!