10" Marconi spark coil

[Alan Douglas]

The man I worked for almost 50 years ago, at Woods Hole Oceanographic Institution gave me this coil a few years back. He had retrieved it from a storeroom at the Midland, Ontario Marconi station in 1950. It had a few problems:


but looks somewhat better now:


I've been making parts for it gradually over the past few years: the ebonite posts for the spark gap first (from 1 1/4" sheet stock I had bought from a surplus dealer decades ago), the remainder of the gap after that, then more recently the missing commutator handle from bone rather than ivory:


The final step was dealing with the cracked casing. The coil had evidently been thrown into the storeroom upside down and left long enough for the wax to run to one end and split the ebonite casing where it had already been splintered. I was able to repair the breaks with epoxy and fiberglass and then turn the casing around so the breaks are toward the back. That occupied a few weeks recently when the temperatures have been below freezing and I couldn't do anything useful outdoors.

There's no continuity through the secondary (which I suppose was why it was scrapped in the first place) but I don't have the urge to run it anyway.