Track Twist in Railways: Causes, Consequences, and Corrections

Track twist refers to the variation in track cant between two fixed measurement points along the railway track. The distance between these points, known as the twist base, remains constant during measurement. For example, if the base is 3 meters, the resulting measurement is termed a 3-meter twist.
Twist faults can occur due to factors such as uneven track settlement, voids beneath sleepers caused by improper packing or ballast displacement, inadequate drainage, or weak track foundations.

You might wonder, “Why does it matter if a track twists a little bit?” Well, a longitudinal twist can lead to uneven wear on wheels and rails, reduce comfort for passengers, and cause unnecessary stress on train components. If you’re still not convinced, just imagine riding on a train that feels like it’s doing the twist dance on every curve! It wouldn’t be a fun ride. following are some reasons behind paying attention to Track Twist:

• 🚆 1. Prevents Derailments: Excessive track twist creates an imbalance in the forces acting on a train’s wheels. This can lead to wheel unloading and, in severe cases, derailments—posing a significant safety hazard.
• ⚙️ 2. Ensures Passenger Comfort: Uneven track geometry results in sudden jolts and instability, making rides uncomfortable for passengers and increasing wear on train components.
• 🛠 3. Reduces Maintenance Costs: Unchecked track twist can accelerate wear on wheels, axles, suspension systems, and tracks, leading to higher maintenance costs and frequent repairs.
• ⏳ 4. Extends Track & Rolling Stock LifeMaintaining proper track geometry helps prolong the lifespan of both the railway infrastructure and rolling stock by minimizing mechanical stress and damage.
• 🌧 5. Identifies Underlying Track Issues Track twist is often a symptom of deeper problems like poor drainage, ballast washout, or foundation instability. Monitoring twist helps detect and fix these issues before they worsen.

Track twist measurement is crucial for ensuring railway safety and maintaining track stability. The twist is the difference in track cant (cross-level) between two points along the track, measured over a fixed distance known as the twist base. In this case, the base is 6 meters.
Here is a Step-by-Step Guide to Measuring Track Twist:

• A track gauge or digital level to measure cant (cross-level).
• A spirit level for accurate readings.
• A 6-meter measuring tape or fixed base points on the track.

• Identify two points on the track that are exactly 6 meters apart

Using the track gauge or digital level:

• Measure the cant at the first point (let’s call it C1).
• Measure the cant at the second point (let’s call it C2).

Track twist is calculated using the formula:

Twist = (C1 - C2) / L

Where:

• C1 = Cant (cross-level) at the first point
• C2 = Cant (cross-level) at the second point
• L = Lenght Between First point and second point

Example:
If
C1 = 10 mm
C2 = 4 mm
L = 6 Meters
then:

Twist = (10 - 4) / 6 = 1 mm/m

After calculating the twist, compare the value with railway safety standards. If the twist exceeds the allowable limit (e.g., **1 in 200 or 15mm per meter** in some standards), corrective action is needed.

Excessive twist can cause:

• Uneven wheel loading, leading to derailments.
• Increased stress on train components, causing faster wear and tear.
• Passenger discomfort due to sudden track irregularities.

The Twist on a Railway Track can be influenced by several factors:

• Track Settling: Over time, the track settles into its foundation, which can cause slight variations in elevation.
• Track Maintenance Issues: Poor alignment during construction or inadequate maintenance can lead to twist accumulation.
• Temperature Variations: Extreme temperature changes can cause the track to expand or contract, leading to twists.
• Uneven Loading: If the track is subjected to uneven weight distribution from passing trains, it can cause the track to twist over time.

If not corrected, twist can lead to:

• Increased Wear: Both the track and train wheels experience increased wear due to uneven pressure.
• Reduced Comfort: Passengers will experience a bumpier ride, which is never fun, especially on long journeys!
• Safety Hazards: Significant twists may lead to track failures or derailments, making it a critical issue to monitor.

Thankfully, longitudinal twist isn’t a permanent condition. Track maintenance teams can correct the twist through several methods:

• Track Realignment: Correcting the alignment of the track by adjusting the rail supports. This involves adjusting the position of the rails, either horizontally or vertically, to remove the twist and restore the correct alignment.
• Tamping: Specialized machinery, called a tamper, lifts and levels the track by adjusting the ballast (crushed stone around the track), correcting any minor twists or misalignments.
• Ballast Resurfacing: Redistributing or adding ballast material beneath the track helps to support the track properly and reduce the chance of twisting.
• Replacements of Track Components: Worn-out components such as rails, ties, or fasteners may contribute to track twist. Replacing these parts can restore proper alignment.
• Stress Adjustments: If thermal expansion or contraction causes the twist, relieving track stress through adjustments like adding expansion joints or modifying rail lengths can fix the issue.
• Continuous Welded Rail (CWR) Adjustments: For tracks with continuous welded rails, loosening and adjusting the rail fasteners can correct the twist and restore proper alignment.
• Use of Track Machines: Machines like rail grinders and rail benders can help correct minor twists by smoothing the rail surface and adjusting the alignment.
• Track Geometry Measurement and Monitoring: Regular monitoring of track geometry can detect track twists early on, allowing for timely and precise corrections.

Regular inspection and maintenance are key to preventing track twists and ensuring the safety and comfort of the rail system.

Track twist may sound like something only engineers need to worry about, but it’s a crucial aspect of maintaining the safety and comfort of train travel. Whether it’s due to track settling, temperature changes, or just the passage of time, understanding and addressing longitudinal twist is vital to keeping trains running smoothly. And next time you’re on a train, think about those tracks and the subtle twist that makes your journey possible—maybe even with a little less twisting and turning.