Cantilever bicycle brake question

[cmcd]

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

 

[cmcd]

https://www.physicsforums.com/attachments/68515

 

[berkeman]

https://www.physicsforums.com/attachments/68515

I get an Error 404 when trying to view the attachment.

 

[cmcd]

http://s1372.photobucket.com/user/cmcdona22/media/002_zpsc67b5154.jpg.html