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Thread: vertical mounted master cylinder.

  1. #1

    vertical mounted master cylinder.

    Hi all out there.

    This is Shawn and i'm involved in KOOKMIN RACING, South Korea.

    I actually participated in 2014 F-SAE Michigan as a manager of brake system, pedal box and business plan presentation.

    One thing i just wanna know about is the vertical mounted master cylinder.

    There were many formula student racing teams designing impressive pedal box and i was kinda blown away by the vertical mounted master cylinder.

    but i don't know how it works. can anybody explain how it works?

    my thought is master cylinders are designed to work horizontally since load is transmitted in a horizontal direction.

    and pedal force and pedal ratio should be considered as well in order to make enough braking force.

    However, it seems like i'm kinda wrong about my theory.

    PLEASE!!!! I'm extremely curious about the system!!!! teach me smart and genius ppl out there!!

    P.S: i know the vertical mounted master cylinder has a bearing at the end of it. so it can move back and forth. but all the load is still in the horizontal direction!!

  2. #2
    Here is a pretty good reference as to the physics of the system. I wish you luck on your studies.

    Kettering University Vehicle Dynamics
    Formula SAE 2010 - 2015
    Clean Snowmobile Powertrain 2012 - 2015

    Boogityland 2015 - Present

  3. #3
    Short answer is that the 'stem' of the pedal is in tension when you press the brakes.
    Make sense?
    Austin G.
    Tech. Director of APEX Pro LLC
    Auburn University FSAE
    War Eagle Motorsports
    Chief Chassis Engineer 2013
    Vehicle Dynamics 2010-2012

  4. #4
    I have never designed a vertical mount system or worked with one, but I believe, as you probably noticed, that the major advantage is the packaging of the system. I would imagine that one could save a few inches in the overall length of the system. I also believe that these vertical MC designs usually utilize a MC that has the rod and piston designed as one piece, rather than separate pieces. and a different balance bar design than the normal balance bar that utilizes a spherical bearing.


    One aspect I am not sure of is how the vertical mount affects the bleeding of the system, which would be an important consideration.

    "since load is transmitted in a horizontal direction"
    I would suggest a FBD.
    Fitz Matush
    Auto Seat Tester

  5. #5

    Brake Bleeding

    Normally the manufacturer will tell you not to angle it past 20 degrees or so or else it will not bleed correctly, but this turns out to be no problem.

    The tricky part is figuring out to make your own cheap trunnion design and not have to buy the AP or Tilton trunnion. That will save you a ton of money.
    Kettering University Vehicle Dynamics
    Formula SAE 2010 - 2015
    Clean Snowmobile Powertrain 2012 - 2015

    Boogityland 2015 - Present

  6. #6

    Thank you for the link. i will look at it!

    BTW, what is the trunnion?

  7. #7


    kinda. but didn't 100% understand the mechanism.

    I still gotta figure out the pedal ratio. as far as i remember, they designed the pedal ratio below 2:1. and the driver can't generate enough braking force.

    perhaps, the bore of MC is small then. but still not enough.

  8. #8

    FBD you mean Free Body Diagram huh?

    yup, i did it before, which is why i kinda don't understand its mechanism.

    can't create enough force. However, it tuned out that they didn't have any big problems with braking test.

  9. #9
    Senior Member
    Join Date
    Sep 2002
    Perth, Western Australia

    You can easily have a high enough pedal ratio. One handy way of thinking about it is that the pedal ratio is roughly the height of the pedal divided by the distance between the pedal pivot and the lower master cylinder pivot. the angle between the master cylinder centreline and the line between the lower pivots will determine rising/falling rate.

    It is a fairly simple geometric problem and you can setup a simple calculation in excel to play around with these variables.


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