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"mains power operated" Bedini motor using 6CA7 tube

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  • RotogenRay
    an appendation

    The 6ca7 isn't "ideal" for running off 160 volts rectified AC line. You're underpowering the tube if you do that.

    Better alternative tubes would be these:


    150-200 v
    110 ma
    1200 reverse voltage

    these have similar characteristics:


    The audio people don't know about them yet, so shh! They are faairly inexensie and not in high demand I don't believe

    As well, I was wrong in my first post- the 6ca7 is not a beam power tube, but plate dissapation is 25 watts, so its able to handle moderate power... in case anyone was gonna correct me...

    Leave a comment:

  • RotogenRay
    Originally posted by patmac View Post

    For application on Water spark plug we need a rectifier robust and durable, what do you know about vaccum tubes as rectifier on high voltage? Can be damaged for high voltage?
    I'm going to take a crack at it (not really knowing much about the water spark plug field) and say you need a mercury vapor arc rectifier

    ***ooh ahh***

    Not necessarily THAT one, but they are pretty robust, though not too quick (this is no thyratron) but you should be using it to charge a capacitor and discharge from there. However, if you do happen to short it, it won't blow the filament to the other end of the tube

    And, if you're clever, you can make one

    But lets look at the options (though I hate that we've deviated from the topic of this post)

    You can go with either a high vacuum triode, such as a 6bK4, 6el4a, or 6bd4a
    These are rated at 27,000 volts and 1.6ma.

    Some mercury vapor arc rectifiers that will work (which are much more robust):

    The 6894 or 6895
    20kV maximum reverse voltage, 1.8 amps average, 8.3 amps peak

    Which should be more than enough for any water spark plug.

    Also, the 575a, or 673 are rated 15kV.

    Much useful information can be found at the site
    data on these tubes can be located in the RCA transmitting tube manual

    Leave a comment:

  • patmac

    For application on Water spark plug we need a rectifier robust and durable, what do you know about vaccum tubes as rectifier on high voltage? Can be damaged for high voltage?

    Leave a comment:

  • "mains power operated" Bedini motor using 6CA7 tube

    I've postulated a method in which one could use a vacuum tube equivalent of the 2N3055 in the SG circuit.

    Of course tubes are high impedance, wheras solid state is low impedance. The inductors- power and trigger coil- would have to be rewound to be a higher impedance- say 5 to 8k ohms. This would as well require the use of something other than a battery, but if you think about it (and I know this will excite some of you out there) You need 150 volts to pass through the tube (lower voltages simply won't pass) And If you rectify the AC line (120 volts) you get 160 volts (because DC voltage is 1.4 times AC)

    So, fir the first time, we have a nearly practical directly interfacable way to hook up such a motor to an AC line. Some things to remember- it takes a two cycles to charge the capacitor when rectifying the AC line- to run most efficiently the motor should run at 1800 pulses a second (or so)

    As well, the "radiant pulse" that comes off the windings which is supposed to be good to charge batteries and capacitors, would be orders of magnituide larger than observed in the solid state circuit. As well, the tube should withstand abuse much better- much much better than any solid state device.

    This could be an interesting way to go for someone in advanced research areas of bedini motors and things.

    Heres the datasheet on that tube:
    6CA7 pdf, 6CA7 description, 6CA7 datasheets, 6CA7 view ::: ALLDATASHEET :::

    Its actually a rather sought after tube for higher end audio amplifiers, a replacement for the 6L6 which ewas used extensively through the 30s.

    Its a beam power tube, and sice the beam is more confined not all of the anode has electron beam hitting it, so it can dissapate more heat, so this tube can handle more power than the 6L6.

    You could, I suppose, try using impedance matching transformers, but I'd just assume redesign the whole circuit rather than add more lossy transformers- especially since this is a largely pulsed circuit, that would throw the timing off.

    Anyhoo, good luck to whoever decided to take on this challenge- its a back burner project for me, but I'll get to it eventually perhaps...