... the Caledonian books I have to see if I can get a good picture of a heel end of a blade. Jim. posted: 7 Nov 2015 21:33 from: Martin Wynne Hi Jim, John, Here is C. J. Allen on the subject, in 1915: 2_071630_310000000.jpg He has two chapters on switches, but this is all I can find about loose-heel joints. Unfortunately there is nothing about Scottish practice. regards, Martin. posted: 8 Nov 2015 11:10 from: John Palmer 2129_080606_330000000.jpg Jim, Martin, This is an extract from J.S.Mundrey's 'Railway Track Engineering', substantial parts of which can be previewed on Google Books. I think it was this that first drew to my attention some of the problems that arise from a wheelset passing over a loose heel joint. There is also a section in the HSE's publication about mine trackwork dealing with loose heel switches containing the following commentary: "136 A loose heel switch can open inadvertently when a vehicle passes over in the facing direction of travel. This is caused ...