Capacitor specs

[Bobbbenner]

I understand that capacitors for use in coil boxes are hard to find?? Where can I find them OR what are the specs for the capacitors so I can find some?

[FATMAN]

Birdhaven Vintage Auto Parts, Colfax, Ia

[Moxie26]

Snyder's antique Auto parts in new Springfield Ohio has the correct capacitors.. .47MF orange drop type.

[Mark Gregush]

Snyder's antique Auto parts in new Springfield Ohio has the correct capacitors.. .47MF orange drop type.

You might post the parts number. I could not find them in the online catalog.
The orange drop number;

CDE418P400V
474K 2040

The orange drop (is a style, not a specific item) are larger than some others sold by vendors such as Langs (they were out of stock about a month ago), so the glass divider needs to come out too.

[Moxie26]

Snyder's 2021 catalog, page T-54 , has the capacitor as part number T-5007-CAP, for $3.50 each .

[Moxie26]

About 3 weeks ago there were posts about newly manufactured coils with defective capacitors... Snyder's does not manufacture those,. ..... but they do supply the correct parts for coils

[Bobbbenner]

Thanks for the information.

[BE_ZERO_BE]

The capacitors that are provided by the Model T suppliers are a custom made capacitor.
They do not cross to a commercial part.

[dykker5502]

Apart from the 0.47 pF, the crucial specification is the capacitors ability to handle quick raises in the voltage (spikes). It is measured in dV/dT (change in voltage pr (milli)second and should have some relatively high values (>400V/mS if memory serves me right) and it is this specification most commercially available capacitors fail on after just a short time.
Then of course the physical size may be of importance. The first type discovered was of the orange drop type and that required some "reallignement" of the interiors of the coil:

From left to right: The original replacement capacitors of "Orange Drop", the later type now flat and approx. same thicknes as the original capacitor, various invalid look-alike capacitors - picture "borrowed" from somehere on the Internet - maybe Steve Jelf?
Then the "coil-gang" discovered another vendor, that could deliver 0.47pF capacitors with the right dV/dT specs, but with a much more attractive geometry. They where flat and with a thickness like the original. That made it very easy to replace them because they fit right away into the void after the original capacitor.
They are not really made to Model T, but the vendors doing them had them in their catalog, and can produce them if you order several 1000! So for each batch the various coil rebuilders have to sign up for a number until there are enough to start a batch. That is probably why they may begin to be out of stock as "crowd-ordering" may be in progress (I for one have not been asked to join, yet, though).

New type of capacitor in the void after the original capacitor