Dumb Question about Coils

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Model T Ford Forum: Forum 2016: Dumb Question about Coils
Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Osterman on Monday, April 11, 2016 - 07:45 pm:

Been planning on building a HCCT with old parts on hand and got to wondering ... isn't there a way to adjust / test coils while they're in the car? The magneto would be running at normal speed and you have both hands free. Can't an ammeter be placed in line to take readings while adjusting.

Remember .. I did say it was a dumb question ... so be gentle.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan B on Monday, April 11, 2016 - 07:49 pm:

I'll be waiting for an answer too Mark.

Thanks for asking


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Garrison - Rice Minnesota on Monday, April 11, 2016 - 07:51 pm:

I certainly have very little if any electronics knowledge and I'm the king of dumb questions but here's my uneducated guess

You'll be attempting to test four coils at the same time unless you can find a way to isolate each individual coil. Or consider four individual test systems. Or...


Top of pagePrevious messageNext messageBottom of page Link to this message  By jon pederson, Minneapolis,MN on Monday, April 11, 2016 - 08:10 pm:


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Monday, April 11, 2016 - 08:11 pm:

I do just that. I have built a box with an AC ammeter in the primary side. I ground the bottom side contact and put mag to the underside contact. Then have a spark gap for the top contact to ground. It will tell you when you are running at 3 1/4 amps and show whether you have a strong spark. However it will not tell you whether you have a double spark. After I test with this box, I try the coil in the car. If it runs smoothly, I use it. It works very well. Maybe not quite as well as a hand cranked coil tester, or a strobospark.
My method will not test the condenser, but a DC ammeter will tell you if it is holding a charge or is open.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Jablonski on Monday, April 11, 2016 - 08:12 pm:

Mark:

Testing coils on a HCCT has the speed restricted to about 60 rpm's, with the ammeter showing 1.3 amps AC average with single sparks...... with the engine running, engine speed would be too fast.

No question is dumb. Remember that.


Bob J.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie B actually in Toms River N.J. on Monday, April 11, 2016 - 08:23 pm:

The question appears to be: " When is not quite good enough good enough"? It's the failure of showing if a double spark exists or not that shies me away from this test. That really is the main check performed by the test units available. Also (in my opinion) the condenser should be changed if it's an existing old style anyway.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Garrison - Rice Minnesota on Monday, April 11, 2016 - 08:26 pm:

Actually Mark, I've wondered the same thing for years but as I said, "I can be the king of dumb questions". However, I'll be keeping an eye on this thread to see what shakes out. Good question!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Osterman on Monday, April 11, 2016 - 09:29 pm:

My intent was to install new capacitors in some old coils and isolate one coils at a time in the coil box with the engine running for adjusting the cushion and points. Guess I'm not sure why testing at a slower speed is better than the real thing.

Is double sparking common? I guess you need a HCCT or ECCT to test for that?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Gary Tillstrom 30 miles N of Memphis TN on Monday, April 11, 2016 - 09:33 pm:

The real answer to your question is yes (sort of) and no. Yes you can vary the current as you stated but you can't balance the cushion spring to ensure you are only getting single sparks.

With the HCCT you are planning to build, the double sparks will be apparent and you can tweak the cushion spring to eliminate.

They are best set outside of the coil box on the tester you are building.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Garnet on Monday, April 11, 2016 - 10:56 pm:

Show us your HCCT workmanship when you're done Mark.

Work on a set of coils right now to run in your car. Replace the capacitors if you wish. Then do whatever adjustment you think is needed to the contact assembly on them. Once all four have been set, throw them in your speedster and try them out in a spirited run - try some hills too. Do this now.

Then when you're finished building your HCCT, grab a different set of four coils, rebuild them, and then adjust them until you get only 16 sparks.

Now throw that set of four coils into your speedster and go for another hard run. You will notice an obvious difference and then you will understand and appreciate the difference between tuning them up via an ECCT, Strobospark or HCCT ... and tuning them via any other method.

Until you experience the difference Mark, you can't appreciate the difference.

It's always a good day when we've learned something!

Regards,
Garnet


Top of pagePrevious messageNext messageBottom of page Link to this message  By JohnH on Monday, April 11, 2016 - 11:28 pm:

It's an interesting question that I once pondered over, adapting the crankshaft pulley to function as the rotating spark gap, to determine the presence of multiple sparking.
The engine would have to run on three cylinders as each coil is tested one by one. For the current measurement, the timer terminal for the particular coil would have to be grounded so the coil fires continuously.
I'm sure it would work as such, but an important limitation is not being able to adjust the coils so that each has identical firing times. For this reason I went down the fully electronic path, along the lines of the ECCT.


Top of pagePrevious messageNext messageBottom of page Link to this message  By George John Drobnock on Tuesday, April 12, 2016 - 08:26 am:

The question asked is valid. Coils can be adjusted in car. My suggestion is go back to the literature of the period - Dykes, Fahnestock, or Page. As I have stated before, "How did these cars last so long with out a microchip?"


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie B actually in Toms River N.J. on Tuesday, April 12, 2016 - 08:43 am:

The question's valid but the results might not be. As in what's good enough. I've heard of a small number of guys setting the coil by ear and swearing to it. You dress/adjust or replace worn points and the car runs better. It would though, wouldn't it? Then you get really lucky and a friend shows up with a HCCT, sets them correctly and you think to yourself after a drive what the hell was I doing? Last line is a true story.


Top of pagePrevious messageNext messageBottom of page Link to this message  By George John Drobnock on Tuesday, April 12, 2016 - 09:11 am:

I have a HCCT. It was given to me years ago by a co-owner of a small town garage. His partner was a factory trained Ford mechanic (I guess that today a factory trained tech) who worked for an early Ford dealership. On taking ownership of the HCCT I was told that it made an interesting conversation piece. Frank McGarvey (1895-1975), the Ford trained mechanic, did not use the HCCT to test coils, for him tuning by ear and on the road was the proper way to set the coils. I sense that in time the microchip technology to set coils will be treated the same as the original HCCT in my ownership. The unit will be seen as a conversation piece.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie B actually in Toms River N.J. on Tuesday, April 12, 2016 - 09:25 am:

George, I believe the guy was just stubborn. Actually I think he was dead wrong. Perhaps didn't understand how to operate the HCCT. I've done a number of coils and out of about 25 only 2 didn't need to be adjusted for not double sparking. All the others did no matter what they sounded like. (new points & condensers in all). You can't tell a double sparker by the sound. Period.


Top of pagePrevious messageNext messageBottom of page Link to this message  By john kuehn on Tuesday, April 12, 2016 - 09:35 am:

In answering the 'supposed' dumb question about adjusting the coils while in the car there is a farm boy answer.
First, make sure they buzz good. Check each one individually by turning the hand crank. While the car is not running of course!

Second, start the car and run it till its warmed up. Smooth out the engine if it needs it by carefully readjusting the coils while the engine is running. In other word doing it 'by ear'.

Now the self appointed engineers and rocket scientists amongst us will violently disagree, but this 'farm boy' method will work for the majority of us.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Strange - Hillsboro, MO on Tuesday, April 12, 2016 - 09:44 am:

"Even stupid questions have answers!" - I wish I had seen that quote years ago, I could have used it in some of my less than pleasant engineering meetings. :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Tuesday, April 12, 2016 - 09:51 am:

The hand cranked coil tester is used to make sure all coils fire at exactly the same time relative to each other. One adjusts the time needed to fire the coil by adjusting the lower bridge of the coil until each coil draws the same amount of current.

When each coil is drawing exactly the same amount of current, all coils fire at exactly the same time.

Bending the lower point bridge down increases both current and time.

Bending the lower point bridge up decreases both current and time.

The upper point bridge is adjusted for double sparking. If one is experienced in adjusting coils you can get pretty good at doing a visual adjustment of the upper follower point so that it operates properly. You will rarely have double sparking once you figure this out.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Gary Tillstrom 30 miles N of Memphis TN on Tuesday, April 12, 2016 - 11:41 am:

Ford wanted their folks to use the HCCT period. It provided one with repeatable performance and ensured the inter-cylinder timing was accurate. Ensuring a car leaving the dealership was running correctly was essential to Fords success.

Tuning a coil "by ear" that produces an intermittent stumble would be a crap shoot at best. You only have a 25% chance of getting the correct one and a 75% chance of screwing up one of the others.


Top of pagePrevious messageNext messageBottom of page Link to this message  By john kuehn on Tuesday, April 12, 2016 - 01:51 pm:

I don't think most farm boys back in the day had a HCCT in the barn.
Their crap shoot method kept their beat up and dirty T's going for many years.
That is if they had good hearing.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Tuesday, April 12, 2016 - 01:58 pm:

Every Ford dealer, and most auto parts stores would have a HCCT. Just like today, most T clubs have one that you can use for free.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Gary Tillstrom 30 miles N of Memphis TN on Tuesday, April 12, 2016 - 02:33 pm:

What note should folks be listening for? C, F sharp, A flat? When you begin to "smooth it out", how do you distinguish the roughness in #3 from say #1.

Back in 2004 when the international tour was in WI, there was a guy with a coupe and every time we stopped he would swap coils, mess with the adjustments, etc. If you got behind him on the hills you were certain to end up on low pedal as that is where he would be.

The thing that amazed me was Don Lang had a HCCT that folks were welcome to use for free and there was no shortage of folks to help him out. Nothing doing, he was content to set them by ear. I even offered to swap him a set of rebuilt coils that were set correctly for $100.

I made sure the rest of the week to not get behind him. I hate low pedal. Good luck with your tuning.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Kossor - Kenilworth, NJ on Tuesday, April 12, 2016 - 02:34 pm:

The HCCT was a very effective tool for its day using coil current as an approximation of the time it takes a coil to fire. but adjusting the coil points for the same coil current only increases the probability the coils would all fire at about the same time relative to each other. That's because coil inductance varies from coil to coil and the points can double spark or arc if the cushion spring is not adjusted correctly. The coil to coil inductance variation is typically minimal for coils of the same manufacturer and era but can vary significantly between coil types. The HCCT is very effective at detecting double sparking which fires a weak spark early (advanced) followed by another weak spark late (retarded) robing the engine of performance. Here is a photos of a normal spark and of a double spark:

Normal spark fires when the coil current reaches 6A with a dwell time of 2.150ms
Normal Spark

The double spark fires at only 4.8A and early, after about 1.6ms and another weak spark late (retarded) after 2.8ms. The HCCT is very good at catching this cushion spring misadjustment.
Double Spark

An arcing spark begins arcing when the current reaches 5.9A after 2.150ms but continues to arc for another 0.5ms before firing a weak spark of 4.5A late, after 2.630ms. Point arcing is an abnormality that gives a bogus HCCT current reading, retards the spark and is not readily displayed by the HCCT. Actually measuring and displaying the coil dwell time to fire will catch this cushion spring misadjustment.
Arcing Spark

(Message edited by mkossor on April 12, 2016)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie B actually in Toms River N.J. on Tuesday, April 12, 2016 - 02:42 pm:

Gary, you're right on. Lead a horse to water ect. I wasn't quite as hard core as your low pedal guy but after my first set of HCCT'd coils I learned darn quick. The HCCT must have been abundantly available way back and I'll lay you $5 most folks knew about it. Some of them just knew better and a buck in my pocket is better than one spent on coils "that work just fine thank you".


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