Code:
Pedal centre to pivot centre 32cm - excuse mixed units - it does not matter
Pedal connection to servo to pivot - 8cm
Therefore my pedal ratio is only 4:1
My master cylinder bore = 22mm = 7/8" = 0.6 sq inch
Now assume:
23” of vacuum
100lbs of applied foot pressure for comparative purposes.
Based on my brake's details:
Booster size “Manual Pressure” “Free Pressure” Total Brake Pressure
7” Metro 666 psi *1 587 psi *2 1253 psi
7” Dual 666 psi 815 psi *3 1481 psi *4
*1 = (100lbs x 4:1) / 0.6sq.inch = 666psi
*2 = Metro booster constant 352lbs / 0.6 = 587psi
*3 = Dual booster constant 490lbs / 0.6 = 815psi
*4 - The dual offers an increase of 18% of the total over the Metro.
Mike - Where did you get the 'constant' figures in the calculation?
I've tried to do the sums my self, but as a bear of very little brain, what little there is is now smoking.
Taking all the figures as stated, I got as far as:
666 psi Manual Pressure.
Metro Boost Ratio is 1:1.9, so total brake pressure is 666 * 1.9 = 1265 psi
Free Presure is then 1265 - 666 = 599 psi.
Then I get confused. I don't know the boost ratio of the dual 7"...