Cantilever bicycle brake question

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Discussion Overview

The discussion revolves around a homework problem involving the mechanics of a cantilever bicycle brake system. Participants are analyzing the forces acting on the brake blocks when a force is applied to the cable, specifically focusing on the calculations related to moments and forces at play in the system.

Discussion Character

  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • One participant states that the force on each string is calculated as 90N divided by 2, resulting in 45N.
  • The same participant provides a formula for calculating the moment at hinge B, using the distance from B and the force acting on the caliper.
  • Another participant attempts to view an attached image but encounters a 404 error, indicating a potential issue with accessing the visual aid provided.
  • A different link to an image is shared, which may contain relevant visual information for the problem.

Areas of Agreement / Disagreement

There is no clear consensus on the solution to the problem, as participants are primarily focused on sharing information and attempting to access visual aids. The calculations presented by the first participant are not challenged, but the discussion remains open-ended without definitive conclusions.

Contextual Notes

The discussion lacks clarity on certain assumptions, such as the exact geometry of the brake system and the conditions under which the forces are applied. The reliance on visual aids for understanding the problem may also limit the discussion.

cmcd
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Homework Statement



A force F of 90N is applied to the cable and each calliper rotates about its hinge at B. With what force does each brake block at A push against the wheel rim?

* Image attached *

Homework Equations



Moment_B = ( Distance from B ) x ( Force acting on calliper perpendicular to mentioned distance )

The Attempt at a Solution



Force on each string = 90 / 2 = 45N

Length of calliper at 45° to hinge B = (50 - 40cos45°) x 10^-3

1_Moment_B = 50 x 10^-3 x 45

2_Moment_B = ( 50 - 40cos45° ) x 10^-3 x F_brakeBlock@A

1_Moment_B = 2_Moment_B

F_brakeBlock@A = 79.549N
 
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https://www.physicsforums.com/attachments/68515
 
cmcd said:
https://www.physicsforums.com/attachments/68515

I get an Error 404 when trying to view the attachment.
 
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Likes   Reactions: 1 person
http://s1372.photobucket.com/user/cmcdona22/media/002_zpsc67b5154.jpg.html
 

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