Sufficient strength to ensure safe operation at the maximum permissible speed and load (reduced wheelset weight).
They should be able to accommodate the vehicle in a straight line and at the same time be able to pass smoothly through curves and turnouts, and should have the necessary resistance to derailment: they should have the advantages of low resistance and good abrasion resistance.
The advantages of low resistance and good abrasion resistance, which require less traction power and increase service life
Rim: The rim is an important part to keep the vehicle running along the rail and prevent the wheel from derailing.
Rolling circle diameter: The diameter of the wheel has its own pros and cons on the vehicle: a small wheel diameter can lower the center of gravity of the vehicle, increase the volume of the vehicle body, reduce the unsprung mass of the vehicle, reduce the fixed wheelbase of the bogie, and can also reduce the weight of the vehicle for subway vehicles. Small building boundaries reduce project costs: However, small-diameter wheels can increase wheel resistance, increase wheel-rail contact stress, cause tread wear faster, and increase the impact on vehicle vibration through track depressions and joints. The advantages and disadvantages of larger wheel diameters are the opposite.
Inside distance of wheelset：
Ensuring a certain clearance between the rim and the rail can.
1.Reduce the abrasion between wheel flange and rail
2.Realise the role of automatic alignment of wheel pairs
3.Beneficial to the safety of vehicles through the curve
4.Favourable to the safe passage of rutting forks
Smoothly through the curve
Calculation of wheel-rail clearance
Standard gauge:1435mm
Inside distance of wheelset:1353mm
Thickness of rim:32mm(single side),64mm(double side)
Chinese wheel-rail gap:9=(1435-1353-64)/2(mm)
European wheel track clearance:5.5=(1435-1360-64)/2(mm )
Cylindrical tread ：(the tread is a flat cylinder without taper, which is favourable to the measurement of rail height deformation on the Japanese rail inspection car)
Cone tread: tread surface with a certain degree of taper
Arc tread: wear type tread, tread surface with arc
Wheels are equipped with rims in order to prevent derailment regardless of the tread shape.
The taper of the tread is the root cause of the recovery and steering function of the wheelset, as well as of the serpentine motion.
High safety against derailment
Strong alignment performance
Good operational stability (no serpentine motion)
Good curve passing performance (less lateral force when passing curves)
Able to pass smoothly through the turnout
Abrasion resistance should be good, and even if abrasion occurs, its shape change should be small.
Difference in performance perception
During wheel traverse, the contact angle difference and rolling radius difference of wheels with wear tread are more variable than those of wheels with tapered tread, which results in less energy input to the vehicle body and less intense vibration of the vehicle body.
Under the appropriate operating speed, compared with the wheels with conical tread, the wheels with wear-type tread have a shorter wavelength and higher frequency of bogie serpentine motion, and are far away from the intrinsic vibration frequency of the vehicle body.
Wheel tread taper
Wheel tread equivalent taper (slope)
Gravity stiffness
Gravity angular stiffness
Reasonable wheel-rail tread pattern can not only slow down the wear and prolong the service life, but also help the vehicle to pass through the curve and reduce the wheel-rail power effect.
As long as the wheel-rail appearance parameters are determined, the use of wheel-rail contact geometry, can determine the wheel pair in different transverse displacement when the wheel tread equivalent slope, equivalent gravity stiffness and equivalent gravity angular stiffness and other parameters
