131 BRAKES - Firewall flexing

Non-engine, eg: aerodynamics, gearboxes, brakes, suspension
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miro-1980
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131 BRAKES - Firewall flexing

Post by miro-1980 » Mon Jan 04, 2010 11:25 pm

Gents,

Recent discussion on another forum (131mirafiori.com) raised a very interesting subject of firewall flexing.

I haven't heard of this before and was scared when some have suggested that the firewall of 131 was not strong enough to resist giving in (flexing) under extreme pressure applied to the brakes structural weakness. I run the picture in my mind and was even more scared imagining that the pressure I apply to the brakes is not 100% applied to the brake pump but to some degree to the firewall. The wall flexes making additional pressure decreasingly effecting my braking. This mental picture scared me even more.

But when I saw the solution to this problem I laughed. Not because it was stupid ( No Sir!) but because it was simple and ingenious !

Look at these pictures and I ma sure you will agree:
FIREWALL FLEX STOPER 1 .jpg
FIREWALL FLEX STOPER 1 .jpg (36.86 KiB) Viewed 3225 times
FIREWALL FLEX STOPER 2 .jpg
FIREWALL FLEX STOPER 2 .jpg (37.1 KiB) Viewed 3225 times
I decided to share it with you as I believe this is a perfect simple solution to a potential safety problem for competition car users.

Miro
www.131abarth.pl
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Guy Croft
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Re: 131 BRAKES - Firewall flexing

Post by Guy Croft » Tue Jan 05, 2010 8:17 am

Interesting observation!

Hopefully no 'bright spark' will question the impact on suspension geometry under braking....


G

miro-1980
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Re: 131 BRAKES - Firewall flexing

Post by miro-1980 » Tue Jan 05, 2010 11:46 am

Guy,

there appear more physics involved in this than I actually expected.

The forces to which the competition car components are exposed to are indeed extreme , and all kinds of things happen.

No wonder there were so many suspension strengthening and brake system reinforcement introduced by the Abarth factory team.

Now I am beginning to understand that rallying that is a real advanced automotive research.

Miro

It follows that you want a to drive a car that has gone through such rallying experience as this confirms the car engineers know the weak spots and have eliminated them.
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robert kenney
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Re: 131 BRAKES - Firewall flexing

Post by robert kenney » Sat Jan 09, 2010 2:40 am

Just a thought. Even though the fire wall will flex and the booster and master cylinder will move away from the pedal pushrod, the force will not be lowered but the pedal stroke will be increased. The reinforcement is a good idea anyway.
Robert Kenney # 111

tmvolumex
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Re: 131 BRAKES - Firewall flexing

Post by tmvolumex » Thu Sep 16, 2010 3:59 pm

Great solution, I would be interested to know just how much the matster cylinder moves under load, can someone with this set up measure it?
By backing off the both a bit, you should be able to determine just how much the brake master cylinder (MC) moves when fully loaded. IE back off the bolt ,ang set a gap of say .100" betwqeen the bolt head and the MC. Then press on the brake pedal and have someone measure the new gap. It will be less than .100" because of the deflection. Difference between the initial gap and loaded gap is the deflection.
tmvolumex
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