... the aspect of bridge that this rail has, something that flatbottom don t have, and that make bullhead so special: the distance between the rail and timber is larger in bullhead case. But what chair is thickier on base to provide the largest clearence? I saw a lot of types in exactoscale, C&L and scalefour society but no measures at all. I ll make 1:64 (s scale) and 1:32 (gauge one) layouts but the indecision about chair is stopping me to progress. 1871_221622_490000000.jpg posted: 23 Apr 2010 01:15 from: Martin Wynne Ewerthon Mota wrote: what chair makes the bottom of the rail be most apart from the top of the timber? Hi Ewerthon, Welcome to Templot Club. The standard base thickness for all bullhead chairs is 1.3/4" (44mm). This is the amount by which the underside of the bullhead rail is raised above the sleeper tops. This "daylight" between the rail and the sleepers and ballast is a characteristic feature of bullhead track -- ...