Coning of Wheel
Coning of wheels is a technic of chamfering the railway wheels to avoid erotion or depreciation to the wheels and tracks. Generally the wheels are prepared conned by a cone of semi-angle. It is totally based on the theory of coning.
Railways wheels are normally bevelled condition that means of a cone of semi-angle of the arrangement of about 1/20 (rad). The rails are also fixed over sleeper at this identical slope angle to the perpendicular position. The basic width of the railway wheel is generally 140 mm in size and the rail top width is approximately 80 mm. The virtual proportions of the region of conjunction between an encumbered wheel and rail reckon is on the exact shapes of the wheel pace and rail top head. It also depends on the extent of the load occupied from train.
Concept of Coning of Wheel
The intermediate space between the inner borders of railway wheel rims and large kept less than the measurement of the actual railway track. As a results in a small gap between the wheel rims and running ends of the steel rails which is approximately equal to 10 mm, on both side. The tread of the wheels is perfectly the dead point centre of the beginning of the rail, since as a result the railway wheel is technically chamfered to keep it in this middle position without any modification. Then the wheels are also beveled at an inclination of 1 in 20 to avoid the erotion.
Benefits of coning the wheel
(a) Coning of wheel actually reduces the depreciation in between of the wheel rims and rails. Depreciation is caused due to the frictional action of rims with inner faces of the rail top portions.
(b) Coning of wheel also gives an separate option of lateral drift movement of the hinge with is wheel.
(c) Coning of wheel also protect, to some extent, the slipping of the wheels from the track.
Ethics of Coning of wheel
Over the railway level track, the moment the hinge loco moves towards one rail side, the railway wheel tread width above the rail steps-up but reduces over the other rail top. This facts the auxiliary movement of wheel and hinge pulls back to its body in originally actual position. It will be possible only if the diameters on both rails are equal to each other and the pressure on both the rails is also same and identical.
In a coiled pathway, because of maximum rigidity of the wheel bottom either of the wheels has chance to slip by a measurement equal to the differentiation of length of that or else the axle has to move outward a little bit so that a tread with longer diameter is formed and lay over the outer rail portions whereas a slighter excess diameter of tread is formed over the inner side of rail.
Consider the diameter of the tread on both the rails is equal, then such cases:
Slip are = Θ(R2 –R1)
The outer Radius calculation, R2 = R=C/2
Inner Radius calculation , R1=R=G/2
G =Gauge measurment
Railway Track measurment
Θ= Angle at centre in radian
Therefore Slip is = Θx G
For B.G railway track; G gauge = 1.676 meters
and Slip value = 2ΠΘ°/360 x 1.676
Where Θ° is = angle centre in degrees about 1°
ΘSlip value = 029 (roughly for 1° of central angel)
Therefore, the slip value is all about. 029 m per degree central angle.
Now chamfering of wheel on bends is not useful as the main principal axle if consists to centrifugal force which proceeds towards the outward rail side the back axle will precede towards the inside rail and the total benefit of coning of wheels cannot be achieved. These are the results in following disadvantages:
(a) Comparatively the outer side of rail will have more pressure while the inner side of rail will have low pressure.