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May 8[edit]

Force-Vector Diagrams (i.e. force calculations)[edit]

I am designing a pedal box for a Formula Student vehicle. If I press the brake pedal with a force, it has to output that force into the piston of a master cylinder. I am trying to do a force-vector diagram, but it's impossible (for me). If it were a the pedal were straight, it would be easy, but it isn't, so it is difficult. I have attached a picture to show the problem, and hopefully you will be able help. I need to work out the three generic equations. Here are the problems:https://fbcdn-sphotos-d-a.akamaihd.net/hphotos-ak-prn2/t1.0-9/10320602_652593664832694_8003566249436072075_n.jpg Thanks 81.110.73.68 (talk) 23:13, 8 May 2014 (UTC)[reply]

Your sketches show forces that contribute to torque or turning moment around a pivot. Torque is the product of the force applied, the length of the lever arm connecting the axis to the point of force application, and the sine of the angle between the force vector and the lever arm. Balancing moments in your first sketch gives

F_x L₁ sine 90° = F_o L₂ sine θ

However before concluding that

F_o = (F_x L₁) / (L₂ sine θ)

I suggest you review these:

The foot pressure F_x is not actually normal (i.e. 90°) to the lever (tilting the pedal surface doesn't change where the point of application is) so the sketch doesn't quite match the mechanics
There must be a return spring whose torque must first be overcome by foot pressure before any force is transmitted to F_o.

Your plans 1 and 2 are classic examples of Levers Classes 1 and 2 respectively. I gave you the reference to Torque first because you will need it to analyze the more complicated third plan where I think you may have missed the need for a sliding joint (elongated hole?). 84.209.89.214 (talk) 13:23, 9 May 2014 (UTC)[reply]

84.209.89.214, you are so awesome!! Thank you so much!! 143.210.123.69 (talk) 13:55, 9 May 2014 (UTC)[reply]