Coning of wheels
"Coning of wheels" is what allows a train to take a turn without slipping off its tracks.
The head or run of wheels of railway vehicles are not made flat but sloped, and this sloping of the surface along the circumference forms a part of a cone (Fig. 1.5). On straight tracks, the coning of the wheels keeps them central, thereby reducing the wear of wheel flanges. If, at any moment, the wheels go out of their central position, they have to tread unequal distances on the rails. The wheels, therefore, retreat till they are at the central position again. This helps in smooth riding.
On curves, the outer rail is longer than the inner rail. The coning of the wheels helps them to take up position, where greater diameter is available, to tread longer distances of outer rail and wheels of smaller diameter cover the smaller distances of the inner rail. This reduces slipping and skidding of wheels, a phenomenon which not only increase resistance in haulage and speed but also causes lot of extra wear on rails and wheels.
On rails laid flat, coning of rails will subject the rails to eccentric loading at the inner edge. This would create problems in both rail design and maintenance. To avoid these, rails are not laid flat but are tilted inwards at a slope of 1:20, which is the slope of the wheel cone. This is calledcanting of rails.
Advantages of coning the wheels
- Coning the wheels reduces the depreciation of the wheel rims and rails. Depreciation is caused because of the friction action of rims with inner faces of the rail top.
- Coning also gives an option of lateral drift of the hinge with is wheels.
- Coning also prevents, to some extent, the slipping of the wheels.
