With welded rail, special anchors that grip the base of the rail right next to each side of a crosstie ("rail anchors") are used at almost every tie in order to constrain lateral movement of the rail and force it to expand vertically rather than horizontally. In southern Arizona on the Union Pacific route through Tucson, daily temperatures can range from 115 in the summer to the low 30s overnight in the winter. The long sections of welded rail in use on this two-track line (former SP Sunset Route) are restrained by rail anchors to prevent or minimize horizontal expansion and contraction. Sometimes extreme heat can cause kinks even in heavily anchored rail, but I have never actually seen this happen on the UP route through Arizona.
|
|
