Templot Club Archive 2007-2020
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posted: 22 Apr 2010 22:08 from: Ewerthon Mota click the date to link to this post click member name to view archived images |
Hello folks, what chair makes the bottom of the rail be most apart from the top of the timber? The photo bellow show more cleary 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  |
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posted: 23 Apr 2010 01:15 from: Martin Wynne
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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 -- in contrast to most types of flat-bottom track where the foot of the rail is flush, or nearly so, to the sleepers. "Bridge" chairs are so-called because they are mainly intended for use on bridges, i.e. metal girder bridges and viaducts. Such bridges usually have longitudinal timbers ("waybeams") running along the top of the girders to which the chairs are fixed. In order to fit, these chairs need to have a wide square footprint instead of the narrow rectangular footprint of the ordinary chairs used on transverse sleepers. Bridge chairs have the same base thickness as ordinary chairs. Bridge chairs have an additional use in pointwork where the square footprint allows them to be fitted closer together than ordinary chairs, like this: chairing_patterns.gif  Bridge chairs are too wide to be used on plain track sleepers which are only 10" (254mm) wide. Pointwork timbers are 12" (305mm) wide, as shown above. regards, Martin. |
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