[DeTomaso] Any interest in dual (no booster) brake MCconversion?
Will Kooiman
will.kooiman at gmail.com
Mon Apr 2 02:40:49 EDT 2012
I agree that you get additional leverage by going with a smaller master
cylinder. The problem I had was finding a smaller master in the style I
wanted.
It wasn't a big deal with me. I wanted to use the Wilwood pedal assembly
anyway.
I don't agree with what you said about an inline cylinder. The rear piston
doesn't push the front cylinder. It is one long shaft with two sets of
sealing rings (square o-rings?). The pedal is pushing both o-rings.
-----Original Message-----
From: detomaso-bounces at realbig.com [mailto:detomaso-bounces at realbig.com] On
Behalf Of Thomas Tornblom
Sent: Monday, April 02, 2012 12:42 AM
To: detomaso at realbig.com
Subject: Re: [DeTomaso] Any interest in dual (no booster) brake
MCconversion?
But wouldn't you just as easy get the additional leverage by going with
a smaller master cylinder?
I see that .75" dia cylinders are mentioned in this thread. I notice
that Wilwood has .625" cylinders, which will provide 44% more pressure,
or leverage, than the .75" cylinders.
And inline cylinders will produce twice the pressure, at twice the pedal
travel, compared to side by side cylinders of the same diameter.
With a side by side arrangement, half of the pedal force goes to each of
the cylinders, if the balance bar is centered.
For an inline cylinder, all of the force is applied to the rear piston,
and the hydraulic pressure in that circuit is then used to move the
front piston, so the rear piston will travel twice as long as the front
piston, and the hydraulic pressure will be the same in both circuits.
Thomas
2012-04-02 06:50, Ken Green skrev:
> Will,
>
> Doing the conversion, it's easy to mount the balance bar and MCs a bit
higher and get the same ratio (I think it's 6.5 to 1) as the Wilwood pedal
assembly. But I think the stock ratio is about 5.5, so it's only about a
20% difference.
>
> Ken
>
> From: Will Kooiman<will.kooiman at gmail.com>
> To: 'Ken Green'<kenn_green at yahoo.com>; 'Guido
deTomaso'<guido_detomaso at prodigy.net>; detomaso at realbig.com
> Sent: Sunday, April 1, 2012 5:20 PM
> Subject: Re: [DeTomaso] Any interest in dual (no booster) brake
MCconversion?
>
> Ken is right.
>
> What everyone is missing, though, is power brakes do not have the same
> leverage built into the pedal as manual brakes.
>
> If you remove the booster and replace it with a manual master, your brakes
> will likely require at lot more force to stop.
>
> That's why I used a Wilwood pedal assembly instead of modifying the stock
> medal box. The Wilwood pedals are designed for manual brakes. They
stopped
> my car very well.
>
> I chose the smallest bore masters, and I was using stock Girling calipers
> with Porterfield pads. I plan on upgrading to Wilwood 6-piston calipers
> (after much deliberation).
>
> -----Original Message-----
> From: detomaso-bounces at realbig.com [mailto:detomaso-bounces at realbig.com]
On
> Behalf Of Ken Green
> Sent: Sunday, April 01, 2012 3:48 PM
> To: Guido deTomaso; detomaso at realbig.com
> Subject: Re: [DeTomaso] Any interest in dual (no booster) brake
> MCconversion?
>
> I know I'm not always right, but I think I am on this.
>
> Maybe I am not understanding what you are proposng? I think that you are
> saying that dual (side by side) 3/4 dia master cylinders will generate
half
> the brake line pressure of a tandem 3/4 dia MC with the safe pedal ratio
and
> same force on the pedal?
>
> I don't think that is correct because the side by side MCs will move the
> same amount of fluid as the tandem MCs for a given pedal movement. I
think
> that utimately, the ratio of pedal force to brake line pressure is
> proportion to the ratio of pedal movement to fluid movement, so the line
> pressure should be the same for side by side, or tandem MCs of the same
> dia..
>
> Ken
> From: Guido deTomaso<guido_detomaso at prodigy.net>
> To: "detomaso at realbig.com"<detomaso at realbig.com>
> Sent: Sunday, April 1, 2012 11:16 AM
> Subject: Re: [DeTomaso] Any interest in dual (no booster) brake MC
> conversion?
>
> "I think you're suggesting you get half the pressure for the same pedal
> force
> and leverage? I don't think that's correct."
>
> Yes, it is.
>
> "A tandem MC has two pistons, and even though they are sequential versus
> parallel, there is still twice the area of each piston. "
>
> No, there's not.
>
> Guess it's not as obvious as I thought. But there's no law requiring you
> understand the underlying principles before building or modifying brakes.
> Many
> here recommend you concentrate braking power at the front of a
> rear-weight-biased vehicle, for example.
>
> GD
>
>
>
> ________________________________
> From: Ken Green<kenn_green at yahoo.com>
> To: Guido deTomaso<guido_detomaso at prodigy.net>; "detomaso at realbig.com"
> <detomaso at realbig.com>
> Sent: Sat, March 31, 2012 2:52:59 PM
> Subject: Re: [DeTomaso] Any interest in dual (no booster) brake MC
> conversion?
>
>
> I think you're suggesting you get half the pressure for the same pedal
force
> and
> leverage? I don't think that's correct. All of this is about leverage, a
> combination of mechanical (the pedal lever arm) and hydraulic (ratio of
> piston
> areas). A tandem MC has two pistons, and even though they are sequential
> versus
> parallel, there is still twice the area of each piston. My personal
> experience
> is that with proper brakes, I never push the pedal much for the brakes to
> come
> on, and once the brakes start to engage, more engagement is much more a
> function
> of force that pedal travel. AND, if there are any problems, I can just
add
> residual valves.
>
> The correlation between dual MCs and the booster is the ugly vs cool
factor,
> and
> more usable front trunk volume. Plus, a booster is a band-aid that falls
> off if
> you loose vacuum. If you engine fails and you hit the brakes, there could
> be
> problems.
>
> Ultimately the test will be how well they work. I have big calipers and
13
> in
> rotors, so I think I will have enough braking. Someone with a lot more
> experience than I have ran the numbers and said with 3/4 dia MCs, I should
> be
> fine with no boost. That also will depend on brake pads, so I see how
well
> it
> works.
>
> Goran has been using a nearly identical system for a long time. It's
> described
> in PI 113 pp 14-15.
>
> Ken
>
> From: Guido deTomaso<guido_detomaso at prodigy.net>
> To: "detomaso at realbig.com"<detomaso at realbig.com>
> Sent: Saturday, March 31, 2012 1:43 PM
> Subject: Re: [DeTomaso] Any interest in dual (no booster) brake MC
> conversion?
>
> Oracle of the obvious, but:
>
> You're combining two unrelated ideas, eliminating the booster and going to
> parallel cylinders.
>
> Each parallel cylinder will only create half the pressure an in-line
> cylinder
> will produce for the same diameter.
>
> Unless you can physically increase the swing of the brake pedal, you'll
> likely
> be chasing your tail: smaller MC(s) , greater leverage ratios and the
pedal
>
> hits the floor before you skid; bigger MC(s), lesser leverage ratios and
you
>
> can't skid since the effort is so high.
>
> While we're in the neighborhood, for all the problems associated with the
> ubiquitous tandem master cylinder ( difficult to bleed, failure of half
the
> system goes unnoticed, expensive, more difficult to rebuild ) ; you don't
> see
> that much conversion back to a single master, pre-'67 arrangement.
>
> GD
>
>
>
> ________________________________
> From: Ken Green<kenn_green at yahoo.com>
> To: "MikeLDrew at aol.com"<MikeLDrew at aol.com>; "detomaso at realbig.com"
> <detomaso at realbig.com>
> Sent: Wed, March 28, 2012 9:11:09 PM
> Subject: Re: [DeTomaso] Any interest in dual (no booster) brake MC
> conversion?
>
> You can easily increase the mechanical advantage by mounting the balance
bar
> a
> bit higher in the pedal arm and mounting the MCs a bit higher.
>
> Next question?
>
>
>
> From: "MikeLDrew at aol.com"<MikeLDrew at aol.com>
> To: kenn_green at yahoo.com; detomaso at realbig.com
> Sent: Wednesday, March 28, 2012 7:37 PM
> Subject: Re: [DeTomaso] Any interest in dual (no booster) brake MC
> conversion?
>
>
>
> In a message dated 3/28/12 19 18 38, kenn_green at yahoo.com writes:
>
>
> I can email photos to anyone interested. It really cleans up the front
> trunk.
> Maybe not a good idea with stock calipers, but if you have big brakes,
seem
> like
>
> the way to go.
>
>
>
> FWIW, Geoff Peters has been struggling to make his GT5 stop after he
ditched
> the
>
> brake booster to save weight (!?)
>
> He's got six-piston Wilwoods on the front and four-piston in the rear. He
> has
> gone through numerous different sized master cylinders in an attempt to
get
> the
> car to stop properly, to no avail. It still requires an enormous amount
of
> pedal effort. I drove the car from England to Modena and back, and it
> wasn't
> nearly as pleasant as it might have been otherwise.
>
> The fundamental problem is that the pedal doesn't have enough mechanical
> advantage. Normally when cars are available either with, or without power
> brakes, they have a different brake pedal depending on the application;
the
> one
> without power has a much higher leverage ratio.
>
> What is your reasoning behind getting rid of the power assist?
>
> Mike
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Real life: Thomas Törnblom Email: thomas at hax.se
Snail mail: Banvallsvägen 14 Phone: +46 18 32 31 18
S - 754 40 Uppsala, Sweden Mobile: +46 76 209 8320
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