[DeTomaso] Any interest in dual (no booster) brake MCconversion?

Mon Apr 2 12:09:12 EDT 2012

To complicate matters aren't many inline dual master cylinders a step bore design for exactly that reason?

Julian

> From: will.kooiman at gmail.com
> To: thomas at hax.se
> Date: Mon, 2 Apr 2012 10:53:05 -0500
> CC: detomaso at realbig.com
> Subject: Re: [DeTomaso] Any interest in dual (no booster) brake MCconversion?
> 
> I see what you mean now. I was thinking both pistons would move at the same
> rate, but it's pretty obvious that the rear would move twice as far -
> assuming the same bore for both.
> 
> And, if the pushrod moves twice as far, the effort would be roughly half.
> 
> Of course, that means it's even more important to have pedals designed for
> your master configuration. Inline masters would need more pushrod travel
> than tandem masters. Conversely, tandem masters need more leverage.
> 
> -----Original Message-----
> From: Thomas Tornblom [mailto:thomas at hax.se] 
> Sent: Monday, April 02, 2012 9:06 AM
> To: Will Kooiman
> Cc: detomaso at realbig.com
> Subject: Re: [DeTomaso] Any interest in dual (no booster) brake
> MCconversion?
> 
> 2012-04-02 15:31, Will Kooiman skrev:
> > I didn't realize they weren't connected, but I don't believe it matters in
> > this discussion.
> 
> It does indeed matter.
> 
> >
> > The force required will be a function of the fluid displaced in the
> masters,
> > which is really just a function of the bore(s). And if you have 2 ports
> > with 2 pistons/o-rings, you displace twice as much fluid - whether they
> are
> > inline or tandem.
> 
> Not correct.
> 
> Run the howstuffworks video, and you'll see that the rear piston moves 
> twice the distance, compared to the front, and all your pedal force is 
> applied to that single piston. In a side by side arrangement, each 
> piston takes half of the force, which makes it twice as heavy for the 
> same diameter cylinders.
> 
> The rear piston displaces twice the amount of fluid compared to the 
> front. It must displace the amount of fluid needed for the calipers in 
> that circuit, as well as the amount of fluid needed to move the front 
> piston, so that it can feed the calipers in that circuit.
> 
> For a side by side arrangement, the piston area needs to be half of the 
> area for an inline cylinder to move an equal amount of fluid into each 
> of the circuits
> 
> The pedal travel/effort in an inline master cylinder will in fact be 
> equal to the travel/effort of a single circuit cylinder. It is the rear 
> piston that does all the work. The front piston is just a safety device 
> which does not change the pedal force/travel needed.
> 
> Cheers,
> Thomas.
> 
> 
> >
> > -----Original Message-----
> > From: Thomas Tornblom [mailto:thomas at hax.se]
> > Sent: Monday, April 02, 2012 2:48 AM
> > To: Will Kooiman
> > Cc: detomaso at realbig.com
> > Subject: Re: [DeTomaso] Any interest in dual (no booster) brake
> > MCconversion?
> >
> > 2012-04-02 08:40, Will Kooiman skrev:
> >> 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.
> >
> > This is not how a standard inline dual master cylinder works, and I
> > doubt that there are any cylinders like that.
> >
> > Check:
> >
> http://auto.howstuffworks.com/auto-parts/brakes/brake-types/master-brake1.ht
> > m
> > http://www.tegger.com/hondafaq/mastercylinderreplace/howworks.html
> > http://www.auto-repair-help.com/automotive_maintenance/master_cylinder.php
> >
> > If both pistons were attached to the same rod, both curcuits would have
> > to take exactly the same amount of flow to engage properly.
> >
> > There may be a rod in between the front and aft pistons, but that is
> > only a fail safe device, in case there is a leak in the rear circuit,
> > the rod will act instead of hydraulic pressure to engage the front piston.
> >
> > Thomas
> >
> >>
> >> -----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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