... , so for example a 1:7 crossing has the knuckle bend curved at 7ft radius. But it's important to get the flangeway gap correct alongside the nose of the vee at X in the diagram, otherwise there is a risk of wheels dropping into the gap in front of it. What you must not do is make the knuckle bend too sharp, as shown by the red line. This is guaranteed to cause problems. 2_050420_590000000.png p.s. Here's a diagram of bullhead rail section, with the thicker edge on top. 2_130841_170000000.png If you have trouble identifying the top edge, try pressing the rail end into a bit of Blu-Tack (or Cheddar cheese) and looking at the impression left. Nowadays for me at least it is easier to see the rail section that way than looking directly at the rail. (40 years ago when I was building track commercially, I could identify the rail just by feel.) The idea of reversing bullhead rail was abandoned because of the indentations in the foot after long use in the chairs. The ...