Variation of friction coefficient
Traction or friction is reduced when the top of the rail is wet or frosty or contaminated with grease, oil or decomposing leaves which compact into a hard slippery lignin coating. ... Locomotives and streetcars/trams use sand to improve traction when driving wheels start to slip.
Why don’t trains slip on tracks?
The wheel bevels are specifically designed so that when the train goes around a corner it stays on the tracks. The wheels that have to travel a greater distance have a greater diameter, and everything stays aligned. The end result is a train that stays on the tracks.
Why do train wheels not slip?
Sliding is prevented by friction and the friction force is equal to the product of the weight – the perpendicular force – and the dimensionless coefficient of static friction.
How do train wheels stay on the track?
To help the wheels stay on the track their shape is usually slightly conical . This means that the inside of the wheel has a larger circumference than the outside of the wheel. (They also have a flange, or raised edge, on the inner side to prevent the train from falling off the tracks.)
Is Train wheel slip bad?
Wheel slip whilst taking power
In traction, low adhesion may cause a wheelset to accelerate more quickly than the train (wheel spin) to the point where it can damage the traction system or result in damage to the wheel and rail (rail burn).
Why does 611 wheel slip so much?
The causes of locomotive wheelslip vary, but the predominant factor lies in the power-to-weight ratios . ... However, if the power of a locomotive vastly exceeds its weight, then an imbalance ensues which causes the violent spinning of the wheels through loss of traction.
What causes wheel slip?
Quite simply, wheel slip occurs when the force applied to a tire exceeds the traction available to that tire . Force is applied to the tire in two ways: Longitudinally — Longitudinal force comes from the torque applied to the tire by the engine or by the brakes. It tends to either accelerate or decelerate the car.
Why do train tracks spark?
The startling moment a train lets off sparks as it’s wheels scrap the tracks has been caught on film. ... ‘ Rails lose their shape over time, due to wheel impact and situations such as extreme heat, vibration and movement . ‘ a spokesperson from Queensland Rail told 7News.
Why do they spray water on train tracks?
Discussed here are characteristics of a water sprinkler which sprays rectangularly distributed water on railway tracks on which high-speed trains run in order to keep snow deposit on them in a wet condition to protect the running gear and underfloor equipment of vehicles from snow damage .
Do bullet trains have wheels?
The shinkansen train uses superconducting maglev (short for magnetic levitation) to achieve these incredible speeds. As the train leaves the station, it’s rolling on wheels . But as it speeds up, the wheels retract, and the power of magnets allows the vehicle to hover four inches above the ground.
How long does a train wheel last?
While many of us change our car tires every 50,000 miles or so, Metro rail wheels can travel as far as 700,000 miles before they need to be replaced. Good thing because changing the wheels on a single rail car can take more than a week , depending on the design of the car.
Why do train wheels click?
Rail squeal is a screeching train-track friction sound, commonly occurring on sharp curves. Squeal is presumably caused by the lateral sticking and slipping of the wheels across top of the railroad track. This results in vibrations in the wheel that increase until a stable amplitude is reached.
Do trains need steering?
Yes , some trains do have what looks like a steering wheel, but the truth is that the wheel is not used for steering. There is a big misconception about this Notch Changer also known as Tap Changer (Speed adjuster) because it does look like a steering wheel.
How does a wheel slip protector work?
How does it work? WSP is a system fitted to most passenger trains to prevent the wheels from locking up due to low adhesion between wheel and rail . ... A signal is then sent to the relevant brake system on the affected bogie or axle, to release the brakes until the wheel returns to normal speed.
What are the rail failures?
The main causes for the failure of rails are as follows. Inherent defects in the rail Manufacturing defects in the rail, such as faulty chemical composition, harmful segregation, piping, seams, laps, and guide marks . ... Derailments Damages caused to the rails during derailment.
What is wheel skidding?
A skid is a loss of traction from a vehicle’s wheels , which can cause it to move uncontrollably.
