"Very sharp" -just means that the power is applied nearly instantaneously. Not any more power, just whatever equals E2 /R. However the temperature gradient would indeed be higher, so the wire would expand sooner than the matrix around. If the matrix temperature rises and falls a lot during a small part of a line cycle, stress might get pretty high. But isn't the wire a near-zero expansion/temperature material?

Ol' Bab -who was an engineer...

On 3/17/2015 4:02 PM, Axil Axil wrote:
In these triac light dimmers, the rise/fall times are very sharp maybe in the nanoseconds. That means that a lot of instantaneous power is being feed into the heater wire as the power pulse starts when the leading edge waveform is used.

On Tue, Mar 17, 2015 at 4:56 PM, Axil Axil <janap...@gmail.com <mailto:janap...@gmail.com>> wrote:

    According to Jack, the reaction did not happen in the fuel, but in
    the insolating layer. The fuel composition does not matter. IMHP,
    what matters is the exact nature of the heater current.

    On Tue, Mar 17, 2015 at 4:38 PM, Robert Ellefson
    <vortex-h...@e2ke.com <mailto:vortex-h...@e2ke.com>> wrote:


        Fantastic! I’m really stoked to hear of your progress.  I
        think your powder recipe sounds very interesting, and I would
        love to know more about the details of the reactants.  It
        sounds like you’ve come up with a mixture which may contain
        one or more key ingredients not yet identified as being of
        primary significance to the high-gain modes of these systems.

        If I may fire away:

        What size Fe2O3 and TiH2 grains were present?

        Is this mixture generally not hygroscopic, and therefore is
        curing the reactor’s sealant a simple matter as compared to LAH?
        Are you tumbling or milling these reactants, or performing any
        other notable processing steps, prior to putting them into the

        Thanks for sharing, and keep up the great work!


        *From:*Jack Cole [mailto:jcol...@gmail.com
        *Sent:* Tuesday, March 17, 2015 1:08 PM
        *To:* vortex-l@eskimo.com <mailto:vortex-l@eskimo.com>

        *Subject:* Re: [Vo]:melted alumina tube


        The input power was ~260W.  I don't know what the R value of
        the insulation is.  I had the cell surrounded by high purity
        alumina powder and covered with a thin sheet of ceramic
        insulation.  I used standard 120V AC 60hz with a triac type
        dimmer switch (chops the waves starting at V=0).  I'll have to
        check with the manufacturer to see what the remaining 5% of
        the tube is.  The heating element was Kanthal A1.  It's
        strange that the heating element was able to completely melt
        at points.  In the past, it has always failed before melting.

        I was using INCO type 255 nickel, TiH2, LiOh, KOH, aluminum
        powder, and Fe2O3.  Good idea on the small amount of fuel
        which should cause some localized melting.

        The fact that the fuel was a small diameter cylinder seems to
        suggest that it was fully expanded in the tube and shrunk down.


        On Tue, Mar 17, 2015 at 2:02 PM, Bob Cook
        <frobertc...@hotmail.com <mailto:frobertc...@hotmail.com>> wrote:


            It looks like you had a pretty good reaction.

            What was the input power?  What is the R value of the
            insulation on the outside of the electric coils?  What was
            the nature of the electrical input--frequency etc? And
            what is the electrical heating element material?   If you
            have an acetylene torch, see if you can melt a piece of
            the tube that melted.

            The tube may have had glass fibers incorporated in order
            to improve strength.  You indicated it was 95% pure.  What
            was the other 5%?

            What was you fuel mixture?  You may want to try a small
            fuel loading and see if the same intense reaction
            happens--all else the same.

            Try the test with a iron core instead of a fuel load and
            determine if there is an apparent magnetic field which
            would hold the iron core in position when direct current
            is applied to the heating coil.  An alternating current
            would of course change the magnetic field and may make for
            null reaction conditions.

             Try 2 or 3 t/c's if you can--one inside and two outside
            to get a measure of the temperature gradient along the
            tube.  Also another easy way to determine temperatures is
            the use of thermal sticks on accessible surfaces.  Welders
            use these to determine preheating temperatures.  They may
            provide a cheap temperature measure for you.

            Keep it shielded--good luck.


                ----- Original Message -----

                *From:*Jack Cole <mailto:jcol...@gmail.com>

                *To:*vortex-l@eskimo.com <mailto:vortex-l@eskimo.com>

                *Sent:*Tuesday, March 17, 2015 9:39 AM

                *Subject:*Re: [Vo]:melted alumina tube

                To add a couple of more details.  The agglomerated
                piece of material is extremely hard.  I tried to break
                it off with pliers, but it seemed like it would take
                more force than to break the entire cell.  The
                resistance wire is extremely difficult to separate
                from the cell. I plan to open the cell with a diamond
                blade later today to see if more can be learned about
                what took place (e.g., evidence of melting on the
                inside of tube). I was able to get one piece of the
                resistance wire pried from the tube.  There were
                indentations in the cell.

                As a follow-up experiment, I need to run it without
                the fuel to the same power levels to see if the same
                effects occur.

                On Tue, Mar 17, 2015 at 9:42 AM, Jack Cole
                <jcol...@gmail.com <mailto:jcol...@gmail.com>> wrote:

                    I had an interesting experiment yesterday.  This
                    was my first time using a triac to regulate input
                    power and sealing the tube with a compression
                    fitting. Unfortunately, my thermocouple failed.

                    Take a look at the alumina tube and the evidence
                    for melting. The furnace sealant which I coated it
                    with completely melted and agglomerated to the
                    bottom of the cell (also appears to be mixed with
                    melted alumina).


                    The tube was purchased from China and is
                    purportedly 95% pure.  It was supposed to have a
                    continuous operating temperature of 1500C.

                    Any opinions?


This email has been checked for viruses by Avast antivirus software.

Reply via email to