key161

This key below is a Marconi Spark key, I found these pictures whilst surfing the net, I can't remember where but apologies if someone recognises them, it looks a real Mans key, really solid, and the contact is a ball bearing! I've admired the lines of this key for a long time, I haven't attempted a copy as sadly I'm pretty sure by looking at it the action won't win any prizes, but I've been looking around for a project to start off in my new workshop, and this old key could be the one.

I'm using Acetal as the base I have cut it to size in the lathe with a slot saw and chamfered the edges in the Mill it looks very smart and precise, being able to cut and clean up a base like this is a pleasure, I am using the original pin pivot design but hiding the pivot points into a sleeve as they look rather ugly otherwise, the picture below shows the pivot point inside the sleeve. and how it looks when assembled

And below a working comparison with the photo, it's always difficult making a key copy this way as judging the scale is a problem, so I shall refer to it as a YUH "Look-a-like" which covers a multitude of sins :)))

And below complete, it has turned into a Brass Monster, a big heavy key, I'm starting to quite like it, long time since I made a heavy Brass pounder great fun :()

And below the ball bearing contact, what became obvious was that the picture had been taken to show the ball bearing by opening the gap to maximum, normally the key would be operated with the bearing almost completely shrouded, other things I noticed were that the rake of the key has to be horizontal so the bearing stays exactly between the two cups that it is positioned in, to much rake and the bearing is struck at an angle which can move it slightly, also I'm not sure if the top cup should be brass, maybe it should be steel, anyway to make the key nicely operational I've put a silver contact in the top cup, as I can't imagine many people using this key to fire up a 20kw spark transmitter!! and that does make the key nicely operational and keep the ball bearing concept, the amount of ball bearings I've lost making this key!! they fly everywhere lucky I have a bag of them :()
I must admit one way to understand a spark key is to build one, the setting up of the pivots to align the contacts AND for minimum friction AND side play would be normal for an operator during the early part of the last century, not sure about today :)))
Anyway it was fun to build, a real cut and thrust cutlass of a key, no finesse in the action but that's how it was designed to be nearly a hundred years ago and the first key completed in my new workshop...