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Dual master cylinder, work when line ruptures?

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  • Dual master cylinder, work when line ruptures?

    sigpic
    Ross.
    Riverside, Ca.
    1957 Provincial X2
    1958 Transtar

  • #2
    I had a '73 GMC pickup that lost the line in the rear. The pedal felt spongy and the braking didn't feel right. When I almost skidded off my driveway and down the mountain, I took time off work to determine the problem. It made me, understandably I'm sure, weak in the knees when the problem revealed itself. I had no brakes in the rear at all. The forward MC reservoir was bone dry. Yes, it will save your bacon, and a few side orders as well.


    Lotsa Larks!
    K.I.S.S. Keep It Simple Studebaker!
    Ron Smith
    Where the heck is Lewiston, CA?
    Home of the famous Mr. Ed!
    K.I.S.S. Keep It Simple Studebaker!
    Ron Smith
    Where the heck is Fawn Lodge, CA?

    Comment


    • #3
      quote:Originally posted by Rosstude
      Ross, that device is not a proportioning valve. I guess you could call it a differential pressure indicator. There is a dumbbell-shaped piston in a bore. One end of the bore is open to front brake line pressure, and the other end to rear brake line pressure. Under normal operating conditions, line pressure is about equal at each end of the bore, and the piston stays put. Given a bad leak on one side, line pressure is vastly unequal (on a brake aplication), and the piston is driven forcefully to the low side, and when it moves, it triggers a switch, which turns on the brake warning lamp. The piston will stay there until it is driven back. That is usually accomplished by: first, repairing the cause of the leak, and second, "cracking" a fitting on the OTHER side, and applying steady brake pressure until the warning lamp is extinguished.

      Gord Richmond, within Weasel range of the Alberta Badlands
      Gord Richmond, within Weasel range of the Alberta Badlands

      Comment


      • #4
        In 1967 the government (NHTSA?)mandated dual chamber master cylinders to prevent a 100% loss of brakes if a line blew (or wheel cylinder failed). Some manufacturers had already gone that route by that time.
        The 'valve' that you see on many vehicles is more of a proportioning valve. It's function it to slightly change the timing of the application of the rear brake. The rear brakes should grab slightly after the front brake. The manufacturers plumbed [u]all</u> the lines (front AND rear) through this valve and also included a small shuttle piston that 'saw' pressure from both the front circuit and the rear circuit. There is a switch plumbed in the middle of this two ended piston. So, if there should be a brake failure due to a loss of line pressure (front, or rear) the shuttle piston would be pushed one way in the bore and this would close the switch contacts and turn the 'BRAKE' light on in the dash to tell you that there is a brake problem (Which you were probably well aware of at that particular time[:0]). Not a bad setup. One thing to make sure of when considering a dual master is that it have residual check valves built in to both the front and rear circuits. Since the master cylinder on many Stude's are mounted below the floor, the master cylinder is actually below the brake caliper and wheel cylinder. This means that air could be pulled into the wheel cylinder or caliper and the master could siphon brake fluid out. A residual check valve will keep either 2psi, or 10psi of line pressure in the lines. Good to keep air out, prevent siphoning, and keep the pistons from retracting.
        Hope the info helps.
        Jeff[8D]


        quote:Originally posted by Rosstude


        DEEPNHOCK at Gmail.com
        Brooklet, Georgia
        '37 Coupe Express (never ending project)
        '37 Coupe Express Trailer (project)
        '61 Hawk (project)
        http://community.webshots.com/user/deepnhock

        HTIH (Hope The Info Helps)

        Jeff


        Get your facts first, and then you can distort them as much as you please. Mark Twain



        Note: SDC# 070190 (and earlier...)

        Comment


        • #5
          Ok, now it's MY turn to be scared. Do you mean to say, Jeff, that if I lost the flex line in the rear of my Daytona wagon(for instance, dual system) that I would lose all pressure?[:0][B)][8] YIKES![:0]


          Lotsa Larks!
          K.I.S.S. Keep It Simple Studebaker!
          Ron Smith
          Where the heck is Lewiston, CA?
          Home of the famous Mr. Ed!
          K.I.S.S. Keep It Simple Studebaker!
          Ron Smith
          Where the heck is Fawn Lodge, CA?

          Comment


          • #6
            What Jeff said about the residual check valves being in both circuits is true when you have drum brakes all the way around. If you have disc brakes up front and drums in the rear, you'll only have the valve on the rear circuit. The shoes on drum brakes move quite a distance compared to discs and they also have a spring to pull the shoes away from the drum when you let up. Discs have very little clearance between the pad and disc when not applied and the only thing that pulls (or pushes) the pad away from the disc when you let up is the lack of any hydraulic pressure and a square rubber seal sort of like a square O ring inside the cylinder that presses tightly around the piston. When you apply pressure, the piston moves forward and slightly deforms the square ring, when you let up, the ring pulls the piston back slightly. That's what makes a disc brake stick when you have rust and crud in the brake cylinder. Hydraulic pressure overcomes the resistance of the crud between the piston and cylinder wall, but when you let up the rubber ring can't over come the resistance and your brake stays partially applied, getting the wheel so hot you could fry eggs on it if you were really hungry but it stinks much worse than frying eggs, melts wheel bearing grease which runs all over your tires and so on. Any one putting disc brakes on a drum system needs to make sure the master cylinder doesn't have a residual valve on that circuit.

            Comment


            • #7
              quote:Originally posted by John Kirchhoff

              What Jeff said about the residual check valves being in both circuits is true when you have drum brakes all the way around. If you have disc brakes up front and drums in the rear, you'll only have the valve on the rear circuit.
              Except...if you have a stock Studebaker disc/drum setup, you will not have a residual check valve in either circuit.

              Also, most modern front disc setups use a 2 pound residual check valve.

              Please, please, please...don't INVENT your own brake set up. Too many variables and too many things that can lead to poor performing or even dangerous brakes. If you want to change things, get the COMPLETE setup from Jim Turner or another Studebaker Vendor that has engineered and tested the combination AND who has an installed base of happy users.




              Dick Steinkamp
              Bellingham, WA
              Dick Steinkamp
              Bellingham, WA

              Comment


              • #8
                Thanks to all for the insights, I do appreciate the help received here.
                I have the complete Turner set up on the Provincial which is what I was working on yesterday. I purchased the deluxe kit, with the master cylinder kit, which included the 2# and 10# residual checks. This is the car my wife, and kid are in each day, as such safety is a top priority, hence the kit from Turner.
                It appears that the valve I recall only(along with proportioning duties) activates a light, and does not isolate the failed circuit.

                [img=left]http://i52.photobucket.com/albums/g27/Rosstude/OldWorld2005002.jpg[/img=left]
                Ross.
                Riverside, Ca.
                1957 Provincial X2
                1958 Transtar
                sigpic
                Ross.
                Riverside, Ca.
                1957 Provincial X2
                1958 Transtar

                Comment


                • #9
                  quote:Originally posted by Rosstude
                  From what you are describing, I assume that you are starting with a
                  system that had no fluid in it? If thats true, air will be in both
                  sides of the master, and the lines, & the pedal will go to the floor.
                  You can get a handy tool from Kragen that is a vacuum pump, you hook
                  it to the bleeder screw and pump up vacuum, than you open the screw
                  and it will draw fluid/air out. Works very nicely. You can get most
                  of the air out before ever having to touch the brake pedal. Then you
                  can pump the pedal for a while and do it the old school way. Once
                  the air is out of BOTH systems, they will function separately & work
                  as your bacon saving feature. With air on the lines both sides will
                  work equally bad.

                  quote:Originally posted by studeclunker

                  Ok, now it's MY turn to be scared. Do you mean to say, Jeff, that if I lost the flex line in the rear of my Daytona wagon(for instance, dual system) that I would lose all pressure?
                  If you have a dual master, losing the rear flex line would only make
                  the rear brakes not work. The fronts will still operate. The flex
                  hose in the rear is just to transfer the rear steel line to the steel
                  lines on the axle and distribute them to the right and left brakes.
                  What Jeff is describing is just how the brakes apply, but the systems
                  are separate in a dual master system. The front brakes do about 75%
                  of the stopping, most rear brakes are only along for the ride and to
                  keep the back end positioned during a stop. What is interesting is
                  the 1995 Impala SS uses the same master and proportioning valve as
                  the base Caprice which is drum brakes. The Impala SS has disc rear.
                  This causes the rear to wear unevenly compared to the front. There is
                  a mod valve bolt available to free up the rear brakes so they work the
                  right way, GM didnt worry about this flaw because it has four wheel
                  anti-lock brakes. Which means it can't lock up anyway!

                  quote:Originally posted by Dick SteinkampPlease, please, please...don't INVENT your own brake set up. Too many variables and too many things that can lead to poor performing or even dangerous brakes. If you want to change things, get the COMPLETE setup from Jim Turner or another Studebaker Vendor that has engineered and tested the combination [u]AND who has an installed base of happy users</u>.
                  Love how you added that last part. Hehe. Nice jab! Kudos to you! I
                  will let you know when I have that happy users part. You let me
                  know when you get Turner's Gtech 60-0 results.

                  Tom

                  '63 Avanti, zinc plated drilled & slotted 03 Mustang Cobra 13" front disc/98 GT rear brakes, 03 Cobra 17" wheels, GM alt, 97 Z28 leather seats, soon: 97 Z28 T-56 6-spd, Ported heads w/SST full flow valves, 'R3' 276 cam, Edelbrock AFB Carb, GM HEI distributor, 8.8mm plug wires
                  '63 Avanti R1, '03 Mustang Cobra 13" front disc/98 GT rear brakes, 03 Cobra 17" wheels, GM alt, 97 Z28 leather seats, TKO 5-spd, Ported heads w/SST full flow valves.
                  Check out my disc brake adapters to install 1994-2004 Mustang disc brakes on your Studebaker!!
                  http://forum.studebakerdriversclub.c...bracket-update
                  I have also written many TECH how to articles, do a search for my Forum name to find them

                  Comment


                  • #10
                    quote:Originally posted by sbca96

                    Love how you added that last part. Hehe. Nice jab! Kudos to you! I
                    will let you know when I have that happy users part. You let me
                    know when you get Turner's Gtech 60-0 results.
                    Tom,
                    I really had no idea you were selling your disc brake conversions. I'm not that interested in Avantis, Camaros and Impala SS's, so I generally skip your posts. I do know you were building a cobra based disc brake set up for your Avanti, but I honestly didn't know you were selling them. My apologies if you felt I was "jabbing" you. My intent was to caution folks about experimenting with their braking system.

                    If you are marketing your brakes and you feel they stop better than your competition, then YOU should probably do some comparison testing with them. Don't wait for ME to do it...it would be a long wait .



                    Dick Steinkamp
                    Bellingham, WA
                    Dick Steinkamp
                    Bellingham, WA

                    Comment


                    • #11
                      Well, if you skip my posts, it explains why you didnt know I just got
                      the first article set from the CNC guy. I am only doing a limited run,
                      to get feedback on how well Studebaker kept their tolerances. As I
                      have stated in the past, not caring what the other guys are doing is
                      how you get left behind. Studebaker isnt around anymore, and we have
                      to get along without them. There is a lot that Studebaker can benefit
                      from things that GM and Ford learned since 1964. I apologize for my
                      jumping to conclusions on your post, it seemed to hit home. This is
                      something that should be of interest to ALL Studebaker owners from '52
                      to '66, since they ALL use the same front suspension. Avantis didnt
                      have an Avanti front suspension. Granted my R1 fuel pump rebuild is
                      an R1 thing, but most applies to the regular V8 pump too. The seats
                      I give you that, not gonna help you out much there. I had a useful
                      diversion from growing up with Studebakers. Whats funny to me, is I
                      get called "Studebaker guy" on the Mustang, Impala, and Camaro forums
                      and I am apparently the "Chevy guy" on here.[B)]

                      I agree .. throwing parts together on a brake system isnt a good plan,
                      its best to use matching parts, and do the proper research.

                      I posted up my Gtech results with the "little" 11 inch GT Mustang disc
                      brakes months ago. I have never seen any results from Turner or from
                      Steeltech. Would be interesting to see on a comparable weight car. I
                      know that my Avanti isnt exactly a lightweight!

                      Tom

                      quote:Originally posted by Dick Steinkamp
                      I really had no idea you were selling your disc brake conversions. I'm not that interested in Avantis, Camaros and Impala SS's, so I generally skip your posts. ... My apologies if you felt I was "jabbing" you. My intent was to caution folks about experimenting with their braking system.
                      '63 Avanti R1, '03 Mustang Cobra 13" front disc/98 GT rear brakes, 03 Cobra 17" wheels, GM alt, 97 Z28 leather seats, TKO 5-spd, Ported heads w/SST full flow valves.
                      Check out my disc brake adapters to install 1994-2004 Mustang disc brakes on your Studebaker!!
                      http://forum.studebakerdriversclub.c...bracket-update
                      I have also written many TECH how to articles, do a search for my Forum name to find them

                      Comment


                      • #12
                        No!
                        With a dual master cylinder (and the appropriate dual circuit plumbing) exactly the opposite.
                        You would have half your brakes, no matter if the failure was in the front, or in the rear.
                        The only connection through the distribution valve (for the front to rear circuits) was through the port
                        that the shuttle piston (and switch).
                        (They call it a warning valve in this pic)

                        If a failure occurs, then the pressure differential would cause the piston to slide over
                        to the failed side (no pressure) and the light on the dash comes on.
                        No fluid loss would occur, as the shuttle piston stops in it's bore.
                        A real good explanation of how a dual circuit master cylinder works can be found here:
                        http://www.tegger.com/hondafaq/maste.../howworks.html
                        Some pretty good basic info can be found at the auto supply store sites....
                        Here's AutoZone's info site...
                        http://www.procarcare.com/icarumba/r...rakes1.asp#top
                        It's worth a read....
                        Jeff[8D]





                        quote:Originally posted by studeclunker

                        Ok, now it's MY turn to be scared. Do you mean to say, Jeff, that if I lost the flex line in the rear of my Daytona wagon(for instance, dual system) that I would lose all pressure?[:0][B)][8] YIKES![:0]


                        Lotsa Larks!
                        K.I.S.S. Keep It Simple Studebaker!
                        Ron Smith
                        Where the heck is Lewiston, CA?
                        HTIH (Hope The Info Helps)

                        Jeff


                        Get your facts first, and then you can distort them as much as you please. Mark Twain



                        Note: SDC# 070190 (and earlier...)

                        Comment


                        • #13
                          there is no warning light on my Studebakers anywhere for failed brakes. Those lights came out in the '70s. I lost a wheel cylindar on one of my Larks once. The pedal went to the floor. I was able to pump up brake pressure and stop the car. It was scary though.


                          Lotsa Larks!
                          K.I.S.S. Keep It Simple Studebaker!
                          Ron Smith
                          Where the heck is Lewiston, CA?
                          Home of the famous Mr. Ed!
                          K.I.S.S. Keep It Simple Studebaker!
                          Ron Smith
                          Where the heck is Fawn Lodge, CA?

                          Comment


                          • #14
                            Your "warning" is when the brakes need to be pumped.[]

                            Tom

                            quote:Originally posted by studeclunker

                            there is no warning light on my Studebakers anywhere for failed brakes.
                            '63 Avanti R1, '03 Mustang Cobra 13" front disc/98 GT rear brakes, 03 Cobra 17" wheels, GM alt, 97 Z28 leather seats, TKO 5-spd, Ported heads w/SST full flow valves.
                            Check out my disc brake adapters to install 1994-2004 Mustang disc brakes on your Studebaker!!
                            http://forum.studebakerdriversclub.c...bracket-update
                            I have also written many TECH how to articles, do a search for my Forum name to find them

                            Comment


                            • #15
                              I never said a Stude had that valve installed OE.
                              The original question went from a single system question, to a dual system question, to a proportioning valve question, then to upgrade possibilities, so I put in the follow up what the industry has done for a more modern brake circuit. I think we all have had our own single circuit failures at one time or another. Investigating the upgrades makes good sense.
                              Jeff[8D]



                              quote:Originally posted by studeclunker

                              there is no warning light on my Studebakers anywhere for failed brakes. Those lights came out in the '70s. I lost a wheel cylindar on one of my Larks once. The pedal went to the floor. I was able to pump up brake pressure and stop the car. It was scary though.
                              HTIH (Hope The Info Helps)

                              Jeff


                              Get your facts first, and then you can distort them as much as you please. Mark Twain



                              Note: SDC# 070190 (and earlier...)

                              Comment

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