Railway Adhesion and Wheel Slip Quiz

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Questions and Answers

What is the effect of wet rails on adhesion?

It increases adhesion significantly.

It stabilizes the adhesion value.

It reduces adhesion. (correct)

It has no effect on adhesion.

What is the relationship between slip speed and maximum creep speed in a stable vehicle operation?

There is no correlation between slip speed and maximum creep speed.

Slip speed must be equal to maximum creep speed.

Slip speed should exceed maximum creep speed for optimal performance.

Slip speed is considered normal as long as it does not exceed maximum creep speed. (correct)

How does an increase in the angle of attack affect adhesion on curves?

It has no effect on adhesion.

It doubles the adhesion value.

It reduces adhesion by half for every 1 degree increase. (correct)

It increases adhesion proportionally.

What does the term 'creep' refer to in the context of rail vehicles?

The difference between wheel speed and ground speed. Signup and view all the answers

Which condition primarily increases the risk of adhesion reduction on the track?

Dry leaves and coal dust. Signup and view all the answers

Which system permits wheel slip at a fixed rate above vehicle speed to control slippage?

Doppler radar based control Signup and view all the answers

What happens to the weight transfer effect as the bogie wheel center distance increases?

It reduces the weight transfer effect. Signup and view all the answers

What characterizes excessive wheel slip in both motoring and braking modes?

One or more spinning axle-wheel sets in motoring mode and sliding in braking mode. Signup and view all the answers

What does sanding do to improve adhesion?

It should be fine, dry sand to enhance adhesion. Signup and view all the answers

Which of the following statements about maximum creep speed is true?

Maximum creep speed depends on track speed and rail conditions. Signup and view all the answers

According to the formula provided, what is represented by µar?

Coefficient of adhesion at a specific speed V. Signup and view all the answers

Which factor does NOT affect the adhesion value according to the content?

Type of locomotive paint. Signup and view all the answers

How does the direction of the traction motor nose affect the load on the axle?

The load on the axle decreases when the nose points in the direction of motion. Signup and view all the answers

What is the formula for traction motor nose force?

TM Nose Force = (1092 / 2) * (6 / 800) Signup and view all the answers

What happens when the gear teeth experience force due to torque exerted by the traction motor?

The force direction on the gear wheel is downwards. Signup and view all the answers

How does the nose-reaction affect the leading axle load in WAG-4 and WAG-5 models?

Nose-reaction is subtractive from the weight on the leading axle. Signup and view all the answers

What is the maximum tractive effort for WAG-7 based on the given formula?

42.5 t Signup and view all the answers

What occurs to the contact between rail and wheel due to vertical shocks?

The contact becomes detached. Signup and view all the answers

What factor contributes to better adhesion and reduced chances of slipping in WAG-7?

Nose-reaction contributing to weight of leading axle. Signup and view all the answers

What is the primary effect of torque exerted by the traction motor on the vehicle?

It results in a vertical load transfer. Signup and view all the answers

In comparison between WAG-5 and WAG-7, what determines the maximum tractive effort?

Net load on each axle. Signup and view all the answers

What is the primary suspension system of WAP 5 and WAG 9 locomotives composed of?

Springs and dampers Signup and view all the answers

How does the steepness of the TE vs Speed characteristic curve affect wheel-slip?

A steeper curve results in quicker wheel-slip arrest Signup and view all the answers

What occurs when the maximum adhesive limit decreases due to factors like dew on the rails?

The wheels start slipping Signup and view all the answers

What is the effect of having traction motors (TMs) in series regarding wheel-slipping?

Current reduction in one TM affects all in series Signup and view all the answers

Which TM configuration is said to provide better adhesion under slipping conditions?

6 P combination Signup and view all the answers

What method of traction control allows for better adhesion in three-phase locomotives?

Continuous step-less control Signup and view all the answers

What happens to the TE when using rheostatic or tap-changer methods for traction control?

TE experiences sudden large variations Signup and view all the answers

Why does increased number of steps in traction control improve adhesion?

It reduces variations in TE Signup and view all the answers

What causes the instantaneous fall in TE that may lead to slipping?

Drops in rail friction Signup and view all the answers

What is the primary function of better elastic suspension in bogies?

Reduces loss of rail-wheel contact Signup and view all the answers

In a WAG-5 bogie, how is the vertical load distributed between the side bearers and the centre pivot?

40% on side bearers, 60% on the centre pivot Signup and view all the answers

Which type of suspension configuration is used for motors in WAG 9 locomotives?

Axle hung nose suspended motors Signup and view all the answers

What is a distinguishing feature of the high adhesion bogies of WAG-7?

Equal distribution of vertical load Signup and view all the answers

What type of suspension system does the WAP-1 and WAP-4 bogies feature?

Primary and secondary suspension Signup and view all the answers

Which component in the WAG-7 bogies carries only traction and braking effort (TE/BE) without vertical load?

Centre pivot Signup and view all the answers

What is a key characteristic of the unequal wheel base in CO-CO trimount bogies of WAG-5?

Affects load distribution efficiency Signup and view all the answers

How many side bearers are present on each bogie of WAG-7?

4 Signup and view all the answers

What role do rubber thrust pads play in the WAG-7's suspension system?

Provide lateral support Signup and view all the answers

In flexi-coil bogies of WAP-1/WAP-4, what does the bolster rest upon?

Helical springs Signup and view all the answers

Which bogie type features a lateral damping mechanism between the body and bogie?

WAG-7 Signup and view all the answers

What is the primary impact of reducing the value of 'h' on weight transfer between the bogies?

It decreases the weight transfer effect considerably. Signup and view all the answers

What percentage of adhesive weight is typically associated with weight transfer between the axles of a conventional design bogie?

15 to 20% Signup and view all the answers

How does vertical coupling between bogies affect vertical reactions due to weight transfer?

It cancels vertical reactions through resilient components. Signup and view all the answers

Which locomotive models incorporate a design feature aimed at reducing the value of 'h'?

WAM 1, WAG 4 Signup and view all the answers

When a locomotive is standing still on level gradient, how is its weight distributed?

It is equally shared by all axles. Signup and view all the answers

What is the effect of turning moments when a locomotive or train begins to run?

They disrupt the static weight distribution. Signup and view all the answers

What is indicated by the low traction base in the context of traction motors?

It minimizes the point of application of tractive effort. Signup and view all the answers

What effect does the direction of the traction motor nose have on the load distribution on the bogies?

It increases the load on the leading bogie when pointing forward. Signup and view all the answers

What happens to the force at the gear teeth when the vehicle moves in the direction opposite to the nose direction?

The reaction on the pinion is downward. Signup and view all the answers

How is the maximum tractive effort for WAG-5 calculated?

By multiplying the number of axles by the maximum load per axle. Signup and view all the answers

In WAN-4 and WAG-5, what is the reaction of nose-reaction and truck-reaction on the leading axle's weight?

Both reactions subtract from the weight on leading axle. Signup and view all the answers

What is the impact of vertical shocks on contact between rail and wheel?

It leads to a temporary loss of contact. Signup and view all the answers

In high-adhesion bogies of WAG-7, how does nose-reaction affect the adhesion?

It adds to the weight on the leading axle, increasing adhesion. Signup and view all the answers

What defines the torque exerted by the traction motor in the context given?

It is influenced by the gear diameter and distance from nose. Signup and view all the answers

How does the weight transfer due to torque exerted by the traction motor affect the axle-loading?

It creates a momentary increase in axle-load when moving forward. Signup and view all the answers

In the calculation for maximum tractive effort, what does 'Min. Net load on axle' imply?

It indicates the effective load accounting for slip conditions. Signup and view all the answers

What is the primary purpose of maintaining an optimal slip speed in rail vehicle operation?

To prevent excessive wheel spin and maintain rail adhesion. Signup and view all the answers

Which factor is NOT associated with peak tractive or braking effort realization?

Exceeding maximum creep speed. Signup and view all the answers

How does a Doppler radar based control contribute to vehicle operation?

It measures vehicle speed and allows slip at a fixed rate above vehicle speed. Signup and view all the answers

What phenomenon occurs when the maximum creep speed is exceeded?

Sudden loss of rail adhesion. Signup and view all the answers

In the context of creeping control, what is the significance of the term 'slip speed'?

The variable indicating the difference between axle speed and vehicle speed. Signup and view all the answers

How is vertical load distributed in the suspension system of the WAG-5 bogie?

60% on side bearers and 40% on centre pivot Signup and view all the answers

What is a distinguished feature of the high adhesion bogies used in WAG-7 locomotives?

Centre pivot carries no vertical load Signup and view all the answers

What percentage of vertical load is shared by the side bearers in WAG-7 bogies?

100% Signup and view all the answers

Which type of bogies feature a bolstering support system?

WAP-1 and WAP-4 Signup and view all the answers

What is the primary reason for wheel-slip to occur when the maximum adhesive limit decreases?

The speed increases and causes traction effort (TE) to fall rapidly. Signup and view all the answers

What is the primary characteristic of the equalizing beam arrangement in the primary suspension of WAG-7?

Supports load through a link and compensating beam Signup and view all the answers

Which configuration of traction motors (TMs) minimizes the impact of one TM slipping on others?

Parallel configuration with multiple TMs. Signup and view all the answers

How many snubbers are there per bogie in the CO-CO trimount bogies of WAM-4 and WAG-5?

4 Signup and view all the answers

How does continuous step-less control in traction systems improve adhesion?

It allows for smooth transitions in traction effort, reducing abrupt variations. Signup and view all the answers

What configuration is characteristic of the flexi-coil bogies found in WAP-1 and WAP-4 locomotives?

Helical springs supporting the primary suspension Signup and view all the answers

What is a key advantage of using a 6 - P configuration of traction motors over a 2 S - 3 P configuration?

It enables better distribution of traction effort across multiple axles. Signup and view all the answers

In WAG-7, what component is responsible for providing lateral dampening?

Lateral dampers Signup and view all the answers

What causes the average value of traction effort (TE) to become much less than the maximum permitted by the adhesive limit?

Large variations in TE caused by discrete steps in rheostatic control. Signup and view all the answers

Which bogie configuration is known for having an unequal wheel base?

CO-CO trimount bogies Signup and view all the answers

In the secondary suspension of WAG-5, what percentage of the vertical load is supported by the centre pivot?

40% Signup and view all the answers

What is primarily affected when one axle's wheel slips in a series configuration of traction motors?

The back-emf and consequently the current in all motors. Signup and view all the answers

Which statement best describes the function of yaw dampers in locomotives?

They enhance the lateral stability of the bogie during high-speed travel. Signup and view all the answers

What is the function of lateral dampers in the suspension system of locomotives?

To reduce vibrations caused by uneven track conditions. Signup and view all the answers

Which type of traction motor configuration is associated with reduced risk of wheel slipping in an operational setting?

Parallel combination with higher torque limits. Signup and view all the answers

How does the steepness of the tractive effort vs speed curve affect overall locomotive performance?

A steep curve leads to quicker responses in decreasing wheel slip. Signup and view all the answers

Study Notes

Adhesion

Adhesion is the force of attachment between wheels and rails, caused by friction.
Adhesion prevents wheel slippage, limiting useful tractive effort for a given axle load.
Factors affecting adhesion include speed, rail condition, weather, and wheel/rail contact.
The coefficient of adhesion (µ) is the ratio of maximum tractive effort (Tmax) to the effective load (W) on the driving axle.
The maximum value of adhesion for steel on steel is 0.44 (or 44%).
Increasing the maximum tractive effort requires more weight on the wheel but this is limited by maximum axle load, which might be needed to restrict curve changes.

Wheel Slip

Wheel slip occurs when the wheels don't adhere fully to the rails, leading to reduced traction.
Damaged gears, bearings, bogie frames, excessive wheel/rail wear, and rail burns are all consequences of wheel slip.
Wheel slip is closely tied to the amount of slip, calculated as (8V/V) x 100% where V is vehicle speed, and 8xV represents the increase in slip speed from the baseline V.

Factors Affecting Adhesion

Speed has an effect on adhesion. Initial adhesion is highest, then it reduces with increasing speed.
Rail condition (wet or oily) and weather (rain, dust) impact adhesion.
Irregularities in the rail/wheel interface, track packing, and curves all reduce adhesion.
Sanding on rails can help improve adhesion.
Adhesion reduces on curves due to angle between the wheel flange and rail gauge face, called angle of attack. A 1 degree increase reduces adhesion by half.

Weight Transfer

Weight transfer happens between bogies and axles in locomotives due to traction exerted by the motors.
It impacts weight distribution, influencing locomotive stability and maneuverability.
Methods include vertical coupling between bogies to reduce transfer, and low traction bars to decrease the height of where the traction force is applied.
Weight transfer depends on locomotive design features.

Suspension Systems

Primary and secondary suspensions are critical parts of locomotive bogies.
They cushion the locomotive body from rail vibrations and shocks.
Their effect on adhesion includes how much the force of adhesion is reduced or lost by the shock between track and wheels.
Different locomotive types (WAM 4, WAG 5, WAG 7) have varying suspension systems, influencing adhesion performance.

Electrical Factors

Traction motor (TM) characteristics are vital for adhesion.
Steepness of the TM's tractive effort vs. speed curve dictates how quickly wheel slip occurs.
Precise control of TM characteristics (e.g., using a switched field method) is key to maintaining adequate adhesion.
The combination of TMs and the way they are wired in series or parallel is crucial to traction forces exerted. TMs wired in parallel are more resistant to wheel slipperiness and loss of adhesion than wiring in series.

Control of Slip and Slide

Monitoring and controlling wheel slip is essential in improving locomotive performance at various operating conditions.
Methods of detecting abnormal wheel-to-rail conditions exist and can be implemented to improve adhesion and mitigate the effects of wheel slip and other negative factors.
Control methods include using radar-based systems or Delta-N controlled systems, which estimate speed, and maintain a stable microslip or creep condition.

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Description

Test your knowledge on the principles of adhesion and wheel slip in rail systems. Learn how these forces affect traction, and explore the factors influencing wheel-to-rail contact. This quiz covers key concepts such as the coefficient of adhesion and the impacts of wheel slip.