Figure $1$ shows calculated rolling radius difference $r_r-r_1$ between right and left wheels, as a function of the wheelset lateral displacement $y$ relative to the track. Calculate the equivalent conicity approximately for lateral displacements $y=+-2mm,$ for the track gauges $1430$ mm and $1436$ mm $.$ If the nominal diameter of the wheelset is $1000$ mm $,$ how tight curves can the wheelset negotiate without flange contact if it is assumed that the flangeway clearance is $12$ mm $?$