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    I am preparing to build another spark transmitter replica for the SPARC museum. I am trying to locate a source for the following materials:
    5/16" X 0.036" half-hard copper strap, or some reasonable approximation.
    Induction motor 1800rpm, salvaged from an attic roof fan for example.
    Any suggestions would be appreciated. Bob Murray

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    flattening some fairly large diameter copper tubing might be one source. If that won’t work I just happened to go to a garage sale and picked up a serving tray made from copper. I bought it figuring it was perfect material to work with for all sorts of little projects. I think the thickness is petty close to what you were looking for.

    heat and quench to make copper soft and heat and cool slowly to make it hard, opposite of steel. perhaps hard and soft tubing has some differences in metalurgy, but I think it’s pretty much true.

    any idea what HP you need for the motor? I assume you want one that looks old, but need very little power because it just turns the rotor? a singer sewing machine motor perhaps?


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    Hi Phil,

    The guy whose project I am replicating used an 1800 rpm induction motor. I assume a fractional hp something like 1/6. It only has to whirl a 10" disc of bakelite through air. The rpm is important because that determines the pitch of the resulting note.


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