MTFCA Forum

Back in the 60's my father made the wood coils, boxes were made from scratch in our shop, I just found a few of these Coil unit capacitors
in a box Black Cat does anyone remember these and how good they were? Bob

I believe that one one of many brand names, including Illini Hycap, Solar, etc. If they're 60 years old, they probably aren't as good as they once were.

The picture shows that the capacity is .25 mfd. Current capacitors have .47 mfd. At .25 they will probably work but maybe not optimally.

Art Mirtes

I find Art’s comment interesting. I have run ‘60’s era distributor “condenser” for about 50 years and they have worked great. I recently had my coils “tuned” on the latest equipment. In doing so we found that the condensers were about the 025 mfd ! The points have survived quite well for about 10,000 miles! I run my 27 roadster on mag (actually generally start it on mag, often hand crank it).
Just thought I would share this experience.

Robert
Those Black Cat brand, film/foil, 400VDC, .25uF dip coated capacitors, have a high enough dV/dT will work fine in a Model T Fordx ignition coil.
Install two and wire them wired in parralel to get the .5 uF specification for the Model T Ford ignition coil.
If your interested in selling them please give me a call.
Ron Patterson
231-348-5085

I've seen these in the black plastic coils. Problem is they used only 0.1uF.

It looks like what the ham's call black beauty's.
when found it radios of that vintage they get replaced.

Les, thank you for that. Very interesting.

I seen it when I got up this morning. Then it beamed up to the Mothership. (Shriners)

I tested several old coils recently and was surprised to find several with .025 capacitors that seemed to work OK.

I had never seen any that size before.

Closest I could find to my question here. Is this the one I need?

TheSpeedsterProject wrote: ↑

Tue Oct 24, 2023 6:45 pm

Closest I could find to my question here. Is this the one I need?

The voltage rating and capacitance are correct, but to use it in a Model T coil requires a high dv/dt rating; something like at least 700uV per microsecond. Unfortunately this specification is often not listed, but it needs to be confirmed before using it. Known suitable capacitors are available from Langs/Snyders, etc.

"CBB Capacitor 474 400V 474J 0.47uF 470nF P15 CL21 Metallized Polypropylene Film Capacitor"

Is that dv/dm/whatever you wrote in that description?

I really need to use that " function here more!

TheSpeedsterProject wrote: ↑

Wed Oct 25, 2023 1:44 pm

"CBB Capacitor 474 400V 474J 0.47uF 470nF P15 CL21 Metallized Polypropylene Film Capacitor"

Is that dv/dm/whatever you wrote in that description?

I really need to use that " function here more!

The only specification there is the capacitance value, tolerance, and voltage rating. However, the fact it's polypropylene means that it might have a high enough dv/dt rating.
Looking at the capacitor from Snyders, https://www.snydersantiqueauto.com/prod ... &cat=41844
we can see it's a Sprague (SBE) product. This has a proper datasheet available. This shows the type 418P capacitor, rated at 0.47uF 400V has a dv/dt rating of 700V/us.
As far as I know, this is also the same capacitor which Langs supplies.

As a point of interest since this supplier no longer exists, Fun Projects also initially supplied the same type: Later they changed to a different narrower type which actually had a higher dv/dt rating. Its advantage was the glass didn't have to removed from the coil to fit it.