Plastic coils died

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Model T Ford Forum: Forum 2012: Plastic coils died
Top of pagePrevious messageNext messageBottom of page Link to this message  By Peter Borland. Bathurst. NSW. Australia. on Thursday, May 17, 2012 - 09:05 pm:

G'day,

Has anybody else had these die unexpectantly?

Spark and buzzing at points, no spark at plugs.

Are they worth repairing?

Peter


Top of pagePrevious messageNext messageBottom of page Link to this message  By Craig Anderson, central Wisconsin on Thursday, May 17, 2012 - 09:28 pm:

Do you have the older ones that were lighter weight and poorly constructed some years ago?
The newer ones are rock solid and considerably heftier than those.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Peter Borland. Bathurst. NSW. Australia. on Thursday, May 17, 2012 - 09:58 pm:

G'day Craig,

Newer unit, purchased last year, done little work, had been sitting in the box they arrived in up to a month ago. Started with a slight surge at higher engine revs on a steady climb, then developed a bad miss and now coil buzzes and sparks at the points but no spark for the plug.

Peter


Top of pagePrevious messageNext messageBottom of page Link to this message  By JohnH on Friday, May 18, 2012 - 01:22 am:

Sounds like a capacitor failure, which may not be surprising, if you run these coils from the magneto. I was under the impression these coils were made for electric fences and the like and thus intended for battery operation only. Certainly, the plastic coils listed by Snyders are stated as being for 6 or 12V which would support this.
It is possible to get away with a lower dv/dt rating for the capacitor when only battery supply is used.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Craig Anderson, central Wisconsin on Friday, May 18, 2012 - 02:07 am:

Do your coils look like these? Do they wear the KW insignia?

http://www.snydersantiqueauto.com/1107


Top of pagePrevious messageNext messageBottom of page Link to this message  By James A. Golden on Friday, May 18, 2012 - 08:23 am:

About 30 years ago, I was told that those black plastic coils were made and tested when new to only operate on 12 volts DC and only to be used on those little yellow railroad repair cars that had four cylinder gas engines. I never learned if four coils were required or just one.

Last year I was surprised to find some of those coils that would draw a normal current on a DC Buzz box and make no sparks at all with a Magneto AC power source or HCCT.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Friday, May 18, 2012 - 04:31 pm:

Peter what you are seeing is a classic example of what happens when you install a metallized capacitor with low dV/dT rating. If you had noticed when you started sparking the coil you would have noticed that the sparking at the points was somewhat minimal compared to the sparking at the points now. What is happening is that the high current spikes are causing "punch through" of the metallized layer inside the capacitor. The layer is being eroded by this action and the capacitor has less and less area and thus becomes a smaller and smaller value capacitor until it essentially evaporates ha ha. I respectfully disagree that you can use a low dV/dT rated capacitor when using battery versus when using magneto. It makes little difference since the capacitor is shorted out by the points and doesn't even enter the picture electrically until the points open and by then the operate current of the coil is high enough to cause damage and it does not matter whether that current came from the magneto or battery. I think a lot of plastic coils were manufactured using the wrong type of capacitor. If I am right you may notice that the capacitor is very small when compared to a typical "orange drop" capacitor or even the newer smaller hi-dV/dT part.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Garnet on Friday, May 18, 2012 - 07:54 pm:

I never used any plastic coil on my railroad jigger - I want something reliable, not disposable, and I never had to change one out, ever! Real railroaders only had a single cylinder, reversible engine too. Anything else was for wussies.

Garnet


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Friday, May 18, 2012 - 08:42 pm:

Garnet:

I make new Fairmont F7996 coils for the Fairmont putt putt cars. Pretty much the same technology as a T coil but in an oak case and with binding posts for the connections.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Robert Hoops - Burton,Texas on Saturday, May 19, 2012 - 08:27 am:

When I bought my '27 about 25 years ago it came with 8 plastic coils but the magneto didn't work. The car was (and is) 6 volts. After I fixed the magneto all 8 of the plastic coils failed in short order. The car runs fine with wooden coils rebuilt by Ron Patterson.


Top of pagePrevious messageNext messageBottom of page Link to this message  By James A. Golden on Saturday, May 19, 2012 - 10:25 am:

Garnet, can you answer the question on whether one or four coils are required for the railroad unit?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Garnet on Saturday, May 19, 2012 - 02:47 pm:

Single cylinder - single coil James.

I do have an old photo somewhere of a custom built jigger with a Model T engine in it. The coilbox is just visible. Obviously it will have four coils but it's not a standard jigger either.

I guess much like the model T itself, anything goes !!

(sorry for the thread drift Peter)

Regards all,
Garnet


Top of pagePrevious messageNext messageBottom of page Link to this message  By Peter Borland. Bathurst. NSW. Australia. on Sunday, May 20, 2012 - 04:39 am:

G'day
thanks for the replies, I have the cover off the coil and will try to dig out the capacitor in one piece to see what it is.
John, the strobo-spark has paid for itself already, a heap of coils given to me that were supposed to be stuffed have been rescued with new points and adjusted on the machine.These coils are now in the '23 and went out for a run today. I could only start on battery and run on the mag before, today I drove on the battery all the way to my destination and only realised that I had not changed to mag when I went to turn her off. I started her on the mag, could not do this before, and drove home and noticed a slight increase in performance, now climbing hills that I once needed to shift down for.
I will gut the coil over the next few days, and post what I find.

Peter


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Sunday, May 20, 2012 - 09:46 am:

Peter
When digging the tar out of a plastic coil stabilize the case with a wood clamp or it will be easily deformed.
1
You find the capacitor tucked away at the top of the case near the four terminal bolts.
2
Be very careful as the wires to the case terminals are much smaller than wood cased coils and can be easily damaged.
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Dewey, N. California on Sunday, May 20, 2012 - 02:08 pm:

The standard belt-drive Fairmount Railway motor cars are one cylinder, two cycle engined. To go forward, you run the engine forward--to go backward, you run the engine backwards. Guys with "broken-in" engines can turn off the ignition, and just as the engine is costing to a stop, throw the spark the other way, turn on the ignition and reverse it. I've not been able to get mine to do that, but then it's only got about an hour of run time on it. BTW, I have model T rings in mine--they fit!
I no longer belong to any motorcar club, and vandals tore up the city owned tracks here, so no place to run the thing. I MAY consider selling it--more $$ for T parts!
T'
David D.
PS, there were a few two cylinder models made, and the later ones used an Onan two cylinder engine with a full transmission. There are also larger models which did have 4 cylinder engines--but "modern" ignition systems.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Peter Borland. Bathurst. NSW. Australia. on Sunday, May 20, 2012 - 11:52 pm:

G'day Ron,

I have removed the side cover and had a small dig. The capacitor is larger than the one in the x-ray. I cannot see a value of it as I need to dig some more and ran out of time. It is large and orange and I will try and have another go at it later this week.

Peter


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