Why Railroads Don't Need Expansion Joints
Practical Engineering
15 min, 53 sec
The video explains the transition from jointed railway tracks to continuous welded rail (CWR) and how railways manage thermal expansion and prevent issues like buckling.
Summary
- Explains why modern trains are quieter without the clickety-clack sound, attributing it to continuous welded rail which eliminates joints that caused noise.
- Demonstrates the concept of thermal expansion and how materials like steel and aluminum expand with heat, explaining it with detailed experiments.
- Introduces the concept of elastic deformation and how tension can elongate materials, and how this principle is used to manage rail stress.
- Discusses the challenges of CWR, particularly buckling due to thermal expansion, and the engineering solutions like using a high neutral temperature during installation.
- Features a sponsorship section by Brilliant.org, emphasizing the value of mathematics in understanding engineering concepts.
Chapter 1
The video starts by addressing the misconception about the iconic clickety-clack sound of trains and introduces the topic of continuous welded rail.
- Addresses the common attribute of the clickety-clack sound associated with trains and clarifies that it's the rails, not the trains, that have changed to be quieter.
- Explains that the sound came from joints in the tracks, which were necessary due to transportation and thermal challenges.
Chapter 2
The segment explains the concept of thermal expansion and its impact on rail joints, demonstrating it with an experiment using an aluminum rod.
- Discusses the concept of an expansion joint and relates it to railways, where gaps between rails allowed for expansion due to heat.
- Uses an experiment with an aluminum rod to show unrestricted thermal expansion and how engineers can predict changes.
Chapter 3
This chapter demonstrates the concept of elastic deformation with an aluminum rod and its relevancy to managing stress in railway tracks.
- Shows how applying tension to a rod can elongate it, illustrating elastic deformation without a change in temperature.
- Explains the concept of restrained thermal expansion, which is used in continuous welded rail to manage expansion without changing the rail's size.
Chapter 4
Explores the issue of rail buckling due to thermal expansion in continuous welded rail and how it is managed through various engineering solutions.
- Explains how rails can buckle under thermal stress and how this is a major concern for railway engineers.
- Details the regulations and procedures followed in the US to manage compressive stress and prevent rail buckling.
Chapter 5
The video discusses the installation techniques of continuous welded rail to manage thermal stress and prevent buckling.
- Describes how railroads use a high neutral temperature during installation to keep rails from undergoing compression.
- Explains the use of heaters, hydraulic jacks, and inspections to ensure rails remain safe and intact in varying temperatures.
Chapter 6
The video concludes with a summary of the benefits of continuous welded rail and includes a sponsorship segment promoting Brilliant.org.
- Summarizes the advantages of continuous welded rail in railway systems, mentioning smoother and quieter rides.
- Promotes Brilliant.org, emphasizing the importance of math in engineering and encouraging viewers to engage with interactive learning.
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