I generally run an 18 psi primary and a 12psi secondary for 30 psi
        total. However the pressure never gets that high as the air spring
        accepts all the coolant expansion without reaching 30 psi.

        Dave Leonard


        --
        Dave Leonard
        Turbo Rotary RV-6 N4VY
         http://members.aol.com/_ht_a/rotaryroster/index.html
        http://members.aol.com/_ht_a/vp4skydoc/index.html


        I don't see how you figure they are in series Dave.
        When the first cap goes off the pressure in the second chamber
        will become 33.5 psi absolute immediately which will over power
        the 12 pound spring in the second cap. These caps operate
        on spring pressure. Here is a diagram.

        BTW do you have a 3 to 4 inch micrometer for measuring the rotor
        housings?

        Paul Lamar ...No rotor no motor.

    ------------------
    Paul, I don't agree with your analysis of the radiator caps
    operation. Let's
    take one cap, venting to atmosphere, The pressure in the system has
    to rise
    enough to overcome the spring + the outside pressure of the
    atmosphere. So,
    with a 10# cap, the pressure must raise to 25 psi (absolute) when
    you are at
    sea level. As you go up in altitude, the *absolute* pressure will
    drop as
    the atmospheric pressure drops.

    Now, lets install a chamber with another (15# ) pressure cap. When
    the first
    cap starts to relieve, it pressurizes the other chamber, and the back
    pressure on the first cap rises.  So the *absolute* pressure in the
    engine
    is = pressure in second chamber + pressure relief of first chamber. If
    sufficient pressure is transferred into the second chamber, then the
    *absolute* pressure in the engine is = atmospheric + pressure relief
    value
    of second cap + pressure relief value of first cap.

    All of this assumes that the flat rubber seal on the cap (that is
    loaded by
    a flat disk spring) can withstand the cap pressures.


    Bill Schertz
    KIS Cruiser # 4045


    Yes that is precisely the problem. I will build a test rig in a few days
    and see how much pressure it will hold. These seals are not designed
    for significant pressure.

    Here is what the test rig  should look like.
    --
    Paul Lamar ...No rotor no motor.

    --------------------------------------------

    Took me all after noon to make this aux pressure
    tank including two trips to the hardware store.. I made it
    out of 1 1/2 " pipe parts and two tubeless tire  schrader
    valves. Holds pressure fine. One must pressure test
    all the parts to make sure none leak or the test of
    the cap is inconclusive.

    I have two caps to test. A 16 psi by CST
    and a 30 psi by C&R racing. I suspect they will all be
    different as there is no specification for holding pressure
    above the pressure release valve. Nor are they expected
    to hold significant pressure in that area.

    I'll hook everything up in a few hours and gets some
    results.
    --
    Paul Lamar ...No rotor no motor.




Paul, I suspect that you are right about the pressure relief area of the
cap.   There seems to be quite a difference between caps in that area.
In other words, some caps I used seemed to leak there, but most did
not.  In order to be more sure about it, I rigged it closed by flowing
JB weld up around the top.

Otherwise, the pressures are in series because the pressure in the
second can is not pressing down on the "diaphragm" in the the first cap,
and adding to its opening pressure.

Yes, I do have a large micrometer for measuring the rotor housings.
Maybe this weekend if I run out of honey do's.