[DeTomaso] Any interest in dual (no booster) brake MCconversion?
Thomas Tornblom
thomas at hax.se
Mon Apr 2 16:20:59 EDT 2012
Piston area in the calipers, and type of brakes (disc/drum), as well as
eventual prop valves in the circuit all affects the about of fluid
flowing in each of the circuits, which affects the piston travel.
Thomas
2012-04-02 18:39, Ken Green skrev:
> Here is an interesting tutorial on tandem (I thought this is the same as
> inline?) MCs:
> http://www.youtube.com/watch?v=VjMotxz--vg
> It looks like the rear piston (and pedal arm) moves farther, but not
> twice as far? However, if you shorten the stroke at the pedal arm (i.e.,
> move the balance bar towards the arm pivot) with dual parallel MCs you
> retain all of the shortened stroke for the pistons.
> I think a stepped tandem MC is equivalent to using MCs with diffent
> bores in the dual parallel MCs setup.
> Ken
>
> *From:* Julian Kift <julian_kift at hotmail.com>
> *To:* will.kooiman at gmail.com; thomas at hax.se
> *Cc:* De Tomaso List <detomaso at realbig.com>
> *Sent:* Monday, April 2, 2012 9:09 AM
> *Subject:* Re: [DeTomaso] Any interest in dual (no booster) brake
> MCconversion?
>
>
> 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 <mailto:will.kooiman at gmail.com>
> > To: thomas at hax.se <mailto:thomas at hax.se>
> > Date: Mon, 2 Apr 2012 10:53:05 -0500
> > CC: detomaso at realbig.com <mailto: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 <mailto:thomas at hax.se>]
> > Sent: Monday, April 02, 2012 9:06 AM
> > To: Will Kooiman
> > Cc: detomaso at realbig.com <mailto: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 <mailto:thomas at hax.se>]
> > > Sent: Monday, April 02, 2012 2:48 AM
> > > To: Will Kooiman
> > > Cc: detomaso at realbig.com <mailto: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>
> [mailto: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 <mailto: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
> <mailto:will.kooiman at gmail.com>>
> > >>> To: 'Ken Green'<kenn_green at yahoo.com
> <mailto:kenn_green at yahoo.com>>; 'Guido
> > >> deTomaso'<guido_detomaso at prodigy.net
> <mailto:guido_detomaso at prodigy.net>>; detomaso at realbig.com
> <mailto: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>
> [mailto: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
> <mailto: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
> <mailto:guido_detomaso at prodigy.net>>
> > >>> To: "detomaso at realbig.com
> <mailto:detomaso at realbig.com>"<detomaso at realbig.com
> <mailto: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 <mailto:kenn_green at yahoo.com>>
> > >>> To: Guido deTomaso<guido_detomaso at prodigy.net
> <mailto:guido_detomaso at prodigy.net>>; "detomaso at realbig.com
> <mailto:detomaso at realbig.com>"
> > >>> <detomaso at realbig.com <mailto: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
> <mailto:guido_detomaso at prodigy.net>>
> > >>> To: "detomaso at realbig.com
> <mailto:detomaso at realbig.com>"<detomaso at realbig.com
> <mailto: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 <mailto:kenn_green at yahoo.com>>
> > >>> To: "MikeLDrew at aol.com
> <mailto:MikeLDrew at aol.com>"<MikeLDrew at aol.com
> <mailto:MikeLDrew at aol.com>>; "detomaso at realbig.com
> <mailto:detomaso at realbig.com>"
> > >>> <detomaso at realbig.com <mailto: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
> <mailto:MikeLDrew at aol.com>"<MikeLDrew at aol.com <mailto:MikeLDrew at aol.com>>
> > >>> To: kenn_green at yahoo.com <mailto:kenn_green at yahoo.com>;
> detomaso at realbig.com <mailto: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
> <mailto: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 <mailto: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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