A brachistochrone subway is not a cost-effective idea - Comments

  • Context: Insights 
  • Thread starter Thread starter rude man
  • Start date Start date
  • Tags Tags
    Brachistochrone Idea
Click For Summary

Discussion Overview

The discussion revolves around the feasibility and cost-effectiveness of implementing a brachistochrone subway system. Participants explore the theoretical implications of the brachistochrone curve in the context of subway design, including speed and distance considerations.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant questions the optimal shape for a brachistochrone subway, suggesting that adding a straight section between the curved halves could maximize speed while adhering to a depth limit.
  • Another participant provides specific timing calculations for a 1600m distance, indicating the time required for both curved and straight sections.
  • A participant expresses appreciation for the insights shared in the discussion, indicating a positive reception of the information presented.
  • One participant acknowledges a previous observation and proposes a title change for their blog to reflect a modified approach to the brachistochrone concept in subway engineering.
  • Another participant simply notes their interest in the topic without providing further details.

Areas of Agreement / Disagreement

The discussion contains multiple viewpoints regarding the design and practicality of a brachistochrone subway, with no clear consensus on the best approach or its cost-effectiveness.

Contextual Notes

Participants reference specific parameters such as depth and distance, but the assumptions underlying these parameters and their implications for design remain unresolved.

rude man
Science Advisor
Insights Author
Messages
8,032
Reaction score
870
rude man submitted a new PF Insights post

A Brachistochrone Subway Is Not a Cost-effective Idea

subwayarticle-80x80.png


Continue reading the Original PF Insights Post.
 
Last edited by a moderator:
  • Like
Likes   Reactions: vanhees71
Engineering news on Phys.org
Where is the point in the circle arcs?
You know the fastest way to get from A to B in general - let the deepest point of the brachistrochrone be at a depth of h. What is the ideal shape if you want to take a longer distance, but with depth limited to h? Well, just add a straight section in between the brachistrochrone halves. It will run at the maximal possible speed, and you already know the first and last part cannot be faster.

For the 1600m distance, you need 22.6 s for the curved sections, and 12 seconds for 800m at 66m/s, for a total of 34.6 seconds.
 
Well this was worth reading i learned something interesting today so thanks for writing this.
 
mfb said:
Where is the point in the circle arcs?
You know the fastest way to get from A to B in general - let the deepest point of the brachistrochrone be at a depth of h. What is the ideal shape if you want to take a longer distance, but with depth limited to h? Well, just add a straight section in between the brachistrochrone halves. It will run at the maximal possible speed, and you already know the first and last part cannot be faster.

For the 1600m distance, you need 22.6 s for the curved sections, and 12 seconds for 800m at 66m/s, for a total of 34.6 seconds.
Good observation. Thanks.
 
Following mfb's observation, the title of my blog should be changed to "Modified Brachistochrone Subway!". mfb has come up with the ideal solution and it resurrects the viability of the Brachistochrone in subway engineering!
 
Interesting topic.
 

Similar threads

  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
  • Sticky
  • · Replies 31 ·
2
Replies
31
Views
16K
  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 15 ·
Replies
15
Views
2K
  • · Replies 18 ·
Replies
18
Views
8K
  • · Replies 21 ·
Replies
21
Views
7K
  • · Replies 15 ·
Replies
15
Views
3K
  • · Replies 25 ·
Replies
25
Views
4K