Plastic Cased Coils….

[MichaelPawelek]

Many moons ago the plastic cased Model T coils on the market were criticized for poor quality and dependability. Do the newer ones sold now work ok?

The reason I ask is that in my area of Texas near the Gulf Coast our heat and humidity cause regular wood cased coils to expand and getting them out of a coil box is sometimes nearly impossible. I have in most cases had to sand down the sides to get them to fit only to find later on they are almost impossible to get back out.

I was thinking the plastic cased coils might save me some grief.
So what does the hive have to say on the subject good or bad?

[jab35]

Michael: Not a direct answer, but if you stopped at Lang's booth in Hershey this week you could have purchased 25 or more plastic coils for $5 each, which to me is not a resounding endorsement of the product. YMMV, jb

[MichaelPawelek]

Wow, That really makes one wonder…..,

[JohnH]

I've just repaired a couple of plastic cased coils - the first I've done. No idea when they were made, but I'm actually very impressed with them. It's a lot easier to change the capacitor since it's smaller and less tar digging is required. Also, the absence of wood breaking, warping, or coming apart makes things easier. The capacitor in the coils I repaired was only 0.1uF at 200V and was a tubular capacitor of "Black Cat" branding. Needless to say, one of them was completely open circuit.
They appear to be wound differently to the wooden coils - I noticed this when setting up for equal firing time; the current builds up at a different rate. Inductance of the primary winding is 2mH, whereas a wooden coil measured 2.6mH. No idea how well they work with a magneto, but certainly for battery operation I don't see any problem with them.

[MichaelPawelek]

John, A picture off the Snyder’s site. Does it look similar to yours?

[JohnH]

Michael, yes the plastic moulding appears to be identical. It would be interesting to know what kind of capacitors are in the current production.

[Luke]

Someone here bought some new (plastic) coils, late 2019 or early 2020 as I recall.

He asked me to test them 'cos they weren't working well. Below is an excerpt of the report:


Three of the coils exhibited capacitance in the range 0.06uF to 0.31uF, one coil was 0.46uF. The expected range is approx 0.42uF to
0.51uF or thereabouts. With new coils I would anticipate 0.47uF +/- 20%.

None of the coils were capable of delivering a good output. Connecting a high-current capable capacitor across the points led to some
improvement.

We inspected one of the points. These showed significant pitting and burning.

Although I have not conducted an ESR test my conclusion at this stage is that, while here could be other issues, all of the coils under test
had poor capacitors. It is likely all the sets of points are also now damaged as a result.

Symptoms of failed capacitors include low output, sparking and rapid points wear, just as these show. Although it appears these are new
coils, with presumably new capacitors, I suggest that they may not be capable enough for this particular task, and should be checked.


I don't recall now who he purchased these from (and wouldn't identify them anyway), but I think he was going to send them back, hence the report as he didn't want to dismantle them etc.

I'd like to think he just got a bad set and that this isn't typical - it will be interesting to read further of others' experience - but early indications would suggest this isn't unusual

Good to read John's comment that they're easily sorted, and that his revelation regarding the capacitor is consistent with what I thought might be the issue. A shame, I'm reminded of that prose "For the want of a nail the shoe was lost etc", if they'd just put in decent caps...

[R.V.Anderson]

My main focus is the early coils, but I rebuild a set of the older style plastic case coils every once in awhile. Everyone who has gotten a set has been very happy with them. Just sayin'.

[Fordwright]

No idea how well they work with a magneto, but certainly for battery operation I don't see any problem with them.

I've wondered about that myself. The magneto produces alternating current, which seems like it might disrupt the resonance between the condenser and the coil. Obviously it works on both AC and DC, but it seems like it would provide a much better spark using DC as a power source.

[jab35]

Greg: Plastic cased coils and wood cased 'ford' coils function alike. On magneto, both types fire during rising or falling portions of the AC voltage wave form. The magnets are 'timed', that is positioned on the flywheel to give 'optimal' but discreet firing times. Ron Patterson has written several articles on this subject, this one addresses your question. jb https://www.modeltcentral.com/support-f ... timing.pdf

[Fordwright]

Greg: Plastic cased coils and wood cased 'ford' coils function alike. On magneto, both types fire during rising or falling portions of the AC voltage wave form. The magnets are 'timed', that is positioned on the flywheel to give 'optimal' but discreet firing times. Ron Patterson has written several articles on this subject, this one addresses your question. jb https://www.modeltcentral.com/support-f ... timing.pdf

I think you're right, and besides, everything I've heard says that the engine runs better on magneto than battery.