HCCT and free air gap

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Model T Ford Forum: Forum 2012: HCCT and free air gap
Top of pagePrevious messageNext messageBottom of page Link to this message  By arnie johansen on Friday, August 10, 2012 - 11:29 pm:

Would one expect a different amp reading if the HCC tester gap was changed from 1/4" to 1/8" while not changing anything of the coil itself that was under test?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Doug Money - Braidwood, IL on Saturday, August 11, 2012 - 12:07 am:

No, because with the HCCT you are reading primary side and the air gap is on the secondary side. The voltage and amps on the secondary side should change with an air gap change.


Top of pagePrevious messageNext messageBottom of page Link to this message  By James A. Golden on Saturday, August 11, 2012 - 02:17 pm:

If you change the HCCT air gap to 1/8", you will have many coils that will pass inspection, but not function well at all and not pass inspection on the Strobo-Spark tester.

The reason is that a much hotter spark is required to jump 1/4" than is required to jump 1/8" and more power (Watts) is required to make that spark hotter, even if the current appears the same.

Been there and done that!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Saturday, August 11, 2012 - 03:05 pm:

Model T coil primary circuit current draw is a function of point adjustment.
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Arnold Wellens on Saturday, August 11, 2012 - 06:01 pm:

Ron and Jim, Do we agree that to get the spark on the HCCT to jump a larger gap we need to adjust the points to increase the current in the primary?

My question is what effect will a low voltage level output of the HCCT magneto have on the adjustment? I am currently working with an HCCT that is putting out about 2 volts at hand crank speed. I plan on correcting this but just haven't gotten to it yet.

(Ron, I haven't worked on the magnets yet)

Arnold


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Cascisa - Poulsbo, Washington on Saturday, August 11, 2012 - 06:18 pm:

The voltage that the HCCT puts out is irrelevant. It is the current (1.3 Amps) that operates the coil regardless of the voltage. If the HCCT produces the necessary 1.3 Amps, then all is well. Some of the HCCTs have voltmeters but they really don't serve any real purpose.

Be_Zero_Be


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Saturday, August 11, 2012 - 08:05 pm:

Arnold
As Bob C. pointed out the Model T ignition coil is a current and not a voltage device.
That is to say when the current in the primary winding rises to the point where the coil points open the secondary winding will develop a voltage based on the applied voltage, ratio of the coils windings multiplied by the "Merit" of the coil.
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Tomaso - Milton,WA on Sunday, August 12, 2012 - 11:24 am:

Bob & Ron - would not the purpose of the voltmeter be to make note of constant voltage (RPM) when hand cranking the tester as opposed to an electric motor run tester as my motorized KRW which is set at a consistent RPM ?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Cascisa - Poulsbo, Washington on Sunday, August 12, 2012 - 02:57 pm:

Steve,

The voltmeter would tend to serve as an indicator of RPM. As RPM increases, the magneto voltage and frequency increases. As the frequency increases, the coil impedance (measured in Ohms) increases, thus the current (1.3 amps), remains the same regardless of voltage and frequency.

The coil is a current operated device. It does not care if the 1.3 amps occurs at a low frequency and low voltage or at a high frequency and high voltage. The end result is the same.

It might be interesting to see if an AC voltmeter could be re-scaled as a tachometer but I think that is a project for another day … :-)

Be_Zero_Be

P.S. are you coming to the Cam-AM tour?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Sunday, August 12, 2012 - 03:22 pm:

A properly adjusted coil will start to fire at about 2 volts ac on the HCCT. As the voltage increases it still fires at 1.3 amps average but operates faster.
Hand cranking the coil tester at a constant speed is preferable AND the meter needle should be very steady at the desired reading and NOT wiggling about. That is an indication the coil is not operating consistently.
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Tomaso - Milton,WA on Sunday, August 12, 2012 - 03:52 pm:

Thank you both for your responses and yes Bob, we are going to the Can-Am - see you there ?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Cascisa - Poulsbo, Washington on Sunday, August 12, 2012 - 05:20 pm:

Steve,

Yes, I will be there. I will be leading the tour on Saturday. See you there :-)

Be_Zero_Be


Top of pagePrevious messageNext messageBottom of page Link to this message  By Garnet on Sunday, August 12, 2012 - 05:54 pm:

Ron, is it just a matter of cushion spring tension that causes the erratic ammeter reading ... too much, too little? After adjusting the current to approx 1.3 amps, the needle is jumping around.

Garnet


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Sunday, August 12, 2012 - 06:17 pm:

Garnet
The major cause of a jittery meter pointer is lack of proper balance between the vibrator and cushion spring causing the coil to not operate consistently.
Add a bit more tension to the cushion spring at it usually settles down. The best tool for that job is CPT-1 from FunProjects.
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Sunday, August 12, 2012 - 06:29 pm:

Garnet
Another thing will cause erratic meter readings; when the cushion spring travel has incorrectly been set greater then the contact point gap.
If you think carefully about point operation I am sure you can imagine it has the same effect as too little cushion spring tension.
Pay very close attention to the cushion spring travel and the contact gap!
When the coil is operating correctly on the HCCT you can listen to the repetitive snap, snap snap of the points and they all sound exactly the same. When wrong you can hear erratic inconsistent noises.
As I love to say; the Model T coil is a trap for logical people and so too is the HCCT. It looks just a bit too simple and the devil is in the details.
After rebuilding 15,621 coils you kinda get a feel for it. Grin
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Garnet on Sunday, August 12, 2012 - 07:02 pm:

I'll try further adjustment of the cushion spring. Initially I'd find the ammeter to be steady but often reading high. After adjusting the current down I'd find the coil firing at every one of the 16 locations but not all the time, and the needle jumping around by 100 ma or so. I thought I'd use NOS contact packs I have on hand but found some of the contacts to have a dull gray coating which inhibited continuity and they had to be cleaned up lightly with emory cloth to work. I do have the CPT-1 (as well as yours).

Garnet


Top of pagePrevious messageNext messageBottom of page Link to this message  By arnie johansen on Sunday, August 12, 2012 - 10:51 pm:

My question still remains: If one changes the gap on the HCCT from 1/4" to 1/8" will the amps reading on the meter change without any change made to the ignition coils settings? I know that the ignition coil may not operate as well in the vehicle but that is not the question. Doug Money answered that the secondary and primary are different circuits and there would not be a change in amp meter reading, but I thought that they are tied together by inductance


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Sunday, August 12, 2012 - 11:58 pm:

Arnie
I tried to answer your question in my post above. The answer to your question is NO!
Your basic understanding of primary/secondary ignition coil winding interaction is wrong.
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Arnold Wellens on Monday, August 13, 2012 - 12:51 pm:

Ron, Would you agree if you are adjusting a coil on a HCCT and it will not jump the 1/4" gap, that if you increase the primary current by adjusting the points you may get it to jump the 1/4' gap?

Would you also agree that a primary current between 1.25 and 1.75 would be acceptable and that each coil should draw the same current?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Doug Money - Braidwood, IL on Monday, August 13, 2012 - 02:57 pm:

One thing to keep in mind, the ignition system never has a need to jump a .250 spark gap. This is merely a test on the HCCT. Changing primary current levels also changes ramp speed which have other side effects.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve in Tennessee on Monday, August 13, 2012 - 06:23 pm:

Ron are you going to paint "20,000" on the coil when you get to that one and personally drive it out of the shop in a T?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Garnet on Monday, August 13, 2012 - 07:38 pm:

I think he should put a rare gold coin in it Steve. Just imagine the backlog at yer local medical centre - everyone who's bought coils from Ron recently would be in there getting their coils put through the CT machine looking for the coin!

... mebbe just a quarter would suffice - then you could say the car's worth a honest buck!

Garnet


Top of pagePrevious messageNext messageBottom of page Link to this message  By Arnold Wellens on Tuesday, August 14, 2012 - 10:39 pm:

Ron, Would you agree if you are adjusting a coil on a HCCT and it will not jump the 1/4" gap, that if you increase the primary current by adjusting the points you may get it to jump the 1/4' gap?

Would you also agree that a primary current between 1.25 and 1.75 would be acceptable and that each coil should draw the same current?


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Wednesday, August 15, 2012 - 03:36 pm:

Arnold:

I will answer your question as best I can. You did not say at what point the current was when you decided to "increase the current to make it jump 1/4". If the coil won't jump 1/4" while it is in your HCCT or Strobo-Spark and the current on the meter says anything between 1.2 and 1.4 then the coil unit is most likely arcing internally at some gap that is less than 1/4". Increasing the current will not fix that. Most T coils will jump well beyond 1/4" at currents even less than 1 amp but the energy in the spark is not as high as with 1.3 which is the nominal design goal set by Ford engineers. Don't confuse spark gap length with spark energy - they are different. You can have a low energy spark that can jump 1/4" and a high energy spark that can jump a lessor gap but is not the gap you want it to jump since you need the energy to be "transportable" from the coil to the spark plug under compression. Providing a place for the spark to jump that is closer than the effective plug gap will cause the cylinder to not get any spark at all and thus misfire because the spark jumped some place else.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Arnold Wellens on Wednesday, August 15, 2012 - 09:39 pm:

John:

Thank you for your answer. I am confused as I always thought the more energy a spark had, the greater gap it would jump. I'm sure I am missing something here. I will try to understand your answer.

Thanks again,

Arnold


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Dufault on Wednesday, August 15, 2012 - 10:06 pm:

John,
Just for comparison, what kind/amount of "energy" in these Tesla coil demonstration sparks?



Dave


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