Aldo Broverone's Opinion on Fulvia Sport

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It´s a pleasure. I hope that i am able to keep you all inform step by step.

regards Andreas

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add. update front suspension

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add update : Brake second serie in first serie Zag

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Brakes

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bullshit rebuilt bottomsheets and the correction of the throttle pedal mounting
and the new tank

Regards to all

Andreas

[Huib]

Looks like you are using a 18 mm master brake cilinder.

If so, did you do the volume calculations for both chambers?

The effective stroke of chamber 1 (normally for 4 pcs 54mm front pots) is 22mm. The stroke of chamber 2 (normally for 4 pcs rear pots of 33 or 35 mm) is 10 mm.

I doubt if chamber 2 is able to reliably pump enough fluid to operate more than 4 small cilinders and one flexible hose.

[racing]

Hi Huib,

it is 18mm and i am in doubt,too. But i have looked on an modern car what mastercylinders they are using. Not more then 18mm and
very short chambers. Toyota for example.

I didn´t calculate it, because for me it is not clear which is the correct volume to calculate with.

Let me say i am accepting that the complett system is full with brake fluid without bracking.If i us the brake then how much is the stroke of the pistons.
Maybe 0,5 mm each, a little bit more or less. And this is maybe the volume i need ?
What do you think about this point of view ?

Maybe i should use 21mm as the second serie´s use to be on te save side but this means i have to modifiy the mastercylinder to fix it on the car
(outer diameter at the end) and also distance of the holes for fixation. Moreover the pedal bolt.
Possible of course but then i have to "destroy"a new master cylinder dia21.

thanks in advance for you answer

regards Andreas

[racing]

dia 18
1,8² x3,14/4 = 2,55 cm² x 2,2 cm = 5,61 cm³ chamber1
2,55 cm² x 1,0 cm = 2,55 cm³ chamber 2

dia 21
2,1²x 3,14/4 = 3,46 cm² x 2,2 cm = 7,61 cm³ chamber1
3,46 cm³ x 1,0 cm = 3,46 cm³ chamber 2

the different is not as big as expeccted

dia 54
5,4²x3,14/4 = 22,9 cm² x 0,05 cm = 1,144cm³ x 4 =4,56 cm³ (should be ok. for the first circle dia18 under condition stroke 0,5 mm )



dia 33
3,3²x3,14/4 = 8,54 cm² x 0,05 cm = 0,427cm³ x 4 =1,7 cm³

dia 35
3,5²x3,14/4 = 9,61 cm² x 0,05 cm = 0,481 cm³x 4 = 1,92 cm³

total 3,6 cm³ (should be not ok for the second circle dia 18 under condition stroke 0,5 mm )


But also for dia 21 the volume of 3,6 cm³ should be not ok for the second circle under condition stroke 0,5 mm

What now.
Check if i am calculate correct. Maybe i made a mistake or the stroke of second serie mastercylinder is higher.
Depent all on 0,5 stroke ofthe pistons. if it is only 0,025 mm everything is fine.

I am intentness

regards Andreas

[Huib]

Hi Andreas

First, I am at present in the hospital. Since over 2 weeks now. Instead of driving a Fulvia or working on a Fulvia.

I did the calculations 2 or 3 years ago as I could not explane braking problems on a GT. I can't find the spreadsheet but remember that with a retraction of only 0,6 mm on all 4 pistons on an axle the corresponding chamber for that axle would run out of business.

This is a mathematical calculation. In real life you have to add:
- wear on the retraction mechanism inside the pistons of the Dunlop brakes
- inflation of the rubber hoses
- inflation of the metal brake lines. Probably a few digits after the decimal point but I am mentioning it nevertheless.
- compression of pads
- flexing of the callipers
- play on wheel bearings (increases retraction)
- wear at the start of the stroke in the master brake cilinder.
- bit of air inside the lines

The retraction on that GT was near to 0,6 on all 4. Since then I measure retraction on all cars that come in for service..

For the Dunlop brakes retraction is specified (see DT) at 0,07 to 0,13mm. This is however influenced by many parts inside the piston and play on the pin in the cilinder.

On modern brakes the retraction is determinded by the trapezium seal sitting in the cilinder near the top.
The cross section of the seal is square but the bottom of the groove is at an angle. Consequently the shape of the groove changes the cross section of the seal into a trapezium.
The angle and corners of the groove determine retraction.

In the seventies as on the S2 brakes the parameters were chosen to give a measurable retraction. Filosophy changed The groove on modern brakes is dimensioned to give no retraction but to give little resistance when the disc pushes the pads backward. This is what I use on the alu cilinders shown on http://www.viva-lancia.com/specials/dun ... inders.htm. Retraction is nil but the wheels turn absolutely freely. The pads still touch the discs but without force. The benefits are that the discs are kept clean and dry.

You mention Toyota as a modern car you have looked at. Its brakes are probably also zero retraction and I bet the rubber brake hoses are less than half the length of the hoses on a Fulvia.

I'll do some calculations in a seperate posting later today.

Ciao, Huib

[racing]

Thanks in advance for you comment and hope that you will soon back in good health.
Moreover i believe that i have to use a 2 series mastercylinder. But i will wait until your response

Best regards
Andreas