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Thread: Exceeding the duty cycle of a Model T ignition coil

  1. #1

    Exceeding the duty cycle of a Model T ignition coil

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    I thought you might like to see a Model T Ford ignition coil that was allowed to continually vibrate operating on battery, got very hot, boiled the tar out onto the top of the box, the remainder of the tar settled into the bottom of the wood box and the wood top of the box finally caught fire.
    Interestingly enough this coil was sent to me a rebuildable coil core.
    Ron the Coilman

  2. #2

    Re: Exceeding the duty cycle of a Model T ignition coil

    I would be embarrassed to send a coil that looked that bad any place but the trash. It does serve as an example.

  3. #3

    Re: Exceeding the duty cycle of a Model T ignition coil

    An experiment with just one coil for the heck of it? I found a patent dated 1906. The patent was for a driver seat adjustment of the coil. As described in the patent for the vibrator or tremble coil to operate it would have 6 volts at 1.5 amps or used about 9 watts of power. As some want hotter sparks and faster turning starts, the voltage is upped to 12 volts. If 12 volts DC is used, this would up the wattage to 18 watts. I would think that taking a coil designed for 9 watts and operated it at 12 volts for the heck of it, the wiring would get hot. So did the individual state what the battery voltage was being used?

    Did the individual try magneto voltage at 30 miles per hour of 26.2 volts AC (or DC) at 9 amps? 235.8 watts for a coil normally operated at 9 watts?

  4. #4

    Re: Exceeding the duty cycle of a Model T ignition coil

    Ron is showing what happens when a coil is left buzzing continuously, which under normal circumstances of a running car, 6, 12 or AC magneto output, would not be a problem. Even a Model T coil running on 6V set for 1.2 to 1.4 amp draw left buzzing will have a melt down as can even the newer oil filled coil if the key is left on and the point are closed. Coils from 1914 up were set on HCCT for best operation and would/should not be readjusted for a hotter spark while in operation.

  5. #5

    Re: Exceeding the duty cycle of a Model T ignition coil

    ......about the adjustment of the vibrator coils. I have a question. Over the 40 years of Model T ownership, I have put together a small collection of "exploding engine" or internal combustion engine repair manuals - dating from 1915 to 1940's. Dykes being the standard reference for most of my Model T repairs and adjustments. Those familiar with Dykes are familiar with their up grading per newer editions of the publication of certain models and manufactures. I do not have all their publications, but the issues I do have and reviewed, including the improved Ford, I never saw reference to the HCCT in Dykes or any other early repair manual. That is until I picked up a copy of "Model T ford Service." And on page 240 there is a picture of a HCCT. No real explanation of what it is called, just that the dealer can make proper adjustments to the coils. Was the HCCT a Ford Dealer proprietary tool? If this test equipment is essential to coil health, why is it so difficult to locate a patent description? If it was in use since 1914, why is it difficult to locate information about a HCCT or related manufacture (Allen?) in early automobile related publications? All my coils have been adjusted with a simple buzz box tester - including a 3 amp meter for current adjustment and a test capacitor. So far I have never had a coil issue. To conclude this long question, yes, I also have a HCCT, it makes a wonderful conversation piece - do I use it to check coils? No.

  6. #6

    Re: Exceeding the duty cycle of a Model T ignition coil

    The HCCT came after 1914 because coils were not being set correctly on buzz boxes. Maybe you could try your HCCT and compare it to your setting using the buzz box. The Model T Ford Service Bulletin Essentials show the HCCT on page 23, dated Tuesday, May 15, 1919. Not much info other then a quick mention and an illustration so they have been around at least that long there must be more info then what was published on an earlier date as the book starts with Tuesday April 1919. Maybe it was a Ford service or authorized service center only tool so information would be transmitted to those people via the Service Bulletins and the Ford Dealer service monthly they would pass the information to their customers.

  7. #7
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    Re: Exceeding the duty cycle of a Model T ignition coil

    Every neighborhood garage would have a hand cranked coil tester by the 1920's. That's why they are so easy to find even today.

  8. #8

    Re: Exceeding the duty cycle of a Model T ignition coil

    I have built and used buzz box testers. About 3 total and that's all I used for years. A few years ago a friend who had an HCCT volunteered to test the coils in my car. Over the course of time he did about 12 coils for me. Out of the dozen only 2 needed no further adjustment. Not a success rate to brag about. By itself the BB only shows that the coil operates not how well it operates. That first set, when replaced in the car, caused it to start from dead cold, hand cranking, on mag. Never did that before for me.

  9. #9

    Re: Exceeding the duty cycle of a Model T ignition coil

    Thank you for you comments. I did see a copy of an advertisement (MTFCA web site) for a HCCT, there was no information as to which publication that it was from, but it was listed to cost about $40.00. If the exchange program is correct and the advertisement was 1921, the local garage owner would have to shell out $522.00 for the tester. At that price they would have a very lucrative shop. I could see Ford Dealers and Service Centres buying a unit. The Ford Owners Manual does state that the dealer has special equipment for testing and adjusting the coils, and indeed the previously referenced service manual does show a picture of a HCCT. For a small local shop to purchase and own a HCCT- it would be a major investment. If they were so popular, why is there more information about a buzz box tester than a HCCT?

  10. #10

    Re: Exceeding the duty cycle of a Model T ignition coil

    Do you have a link to that page?
    If you have a copy of The Model T Ford Owner by Murray Fahnestock, read pages 206 to 210. The first line in the first paragraph is; "Anyone can adjust the Ford coil units- so that they will work like a doorbell! The rest of the information goes on to describe the proper setting of the points and using a HCCT to check them.
    I don't know why there is more information on the buzz box coil checker, but my guess is people didn't know any better and bought a lot of them so there were several makers and a lot of them out there.
    I guess for many years after the T era that's what people had to work with and may never had well running cars. Who cares it's just an old Model T, right! After rediscovering information a such as the Model T Service, Model T Ford Service Bulletin's and Murray's writings we got and are able to pass on the information that Ford intended to be use to set the coils properly. With the internet we can pass on good information (as well as bad) to more people.

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