FYI Distributor Plug

[MikeK]

I believe the original plug was Chatterton's compound, a mix of gutta percha, stockholm tar, and rosin. The gutta percha content (a tree protein material similar to raw latex) prevented the material from becoming too rigid, crystalline, and cracking out.

The average Chatterton's flow temperature was about 260F. Many lead-acid batteries had the cell posts sealed into the top hard rubber cap with this stuff, not the straight tar used for setting the entire cell assembly in the case.

The thick molten material was likely poured into the condenser holes, backed by the fiber washer therein, with the dizzy body sub-assemblies on their sides and moving along an assembly line. That would account for the dome-like appearance seen on some original dizzys. Other originals appear to have had the material pressed or sealed with a cold iron, leaving a flatter plug appearance with indication of the cold tool having a chamfered edge.

Chatterton's was in common use for electrical work in the 20's. Chatterton's and sheets of gutta percha were used to seal splices in generating plants and in underground feed tunnels. An old trick when sealing the leads out of an iron frame motor was to work the Chatterton's with a well-tinned hot iron, which the compound would not stick to.

Side note: In french speaking nations common electrical tape is referred to as "chatterton's" despite the fact that it is not the material of old: "Le ruban adhésif pour électricien est appelé couramment chatterton du nom de son inventeur, un Britannique. Son mélange de goudron, de résine et d’une gomme en latex appelée gutta-percha en fait un atout indispensable pour tout électricien."

As to the rubber plug in question, the A's never used pre-formed removable pop-in plugs.