owbow

right, i've already answered this question but i'm a little dubious at the answer...


10. In a hydraulic brake system on a ProDrive Rally Car, a force of 280N is applied at the brake pedal, which has a leverage of 5:1. The Diameter of the master cylinder is 28mm, whilst the diameter of the 16 wheel cylinder pistons is 40mm. the total efficiency of the system is 88%.

a. what is the Total force exerted by the pistons
b. what is the pedal travel if each piston moves 0.2mm

hmmm i seem to get pedal travel of 52.25cm?????? or is it just a crap question?

thanks
Owain

AvalancheS8

O.K.
1)

280N @ pedal, 5:1 lever.

280*5 = 1400 N @ master cyl

Area of Master Cyl = 28^2*(pi/4) = 615.75mm^2

Therefore fluid pressure raised in master cyl = 1400 / 615.75 = 2.273 N/mm^2

Area of caliper pistons = 40^2*(pi/4) = 1256.64 mm^2 each
Total area of caliper pistons = 16*1256.64 = 20106.12 mm^2

Given system pressure of 2.273 N/mm^2 force produced by pistons

F=20106.12*2.273 = 45701.376 N

Efficiency =88%, Therefore actual total force applied = 45701.376*.88 = 40217 N

2)

Each piston moves 0.2 mm, therefore volume of fluid moved V= 0.2*20106.12

V=4021.2 mm^3

Therefore movement of master cyl to displace this volume
= 4021.2/615.75 = 6.53 mm

5:1 lever on pedal therefore movement at pedal = 6.53*5 = 32mm