Gibson's Worm Gear Tuners
Getting my mettle on metal
Looking at making the Salter, the hardest part for me is definitely going to be the tuners. The instrument will look very different with a pegbox and 10 pegs, and modern tuning machines will seem very out of place, so I’m attempting to replicate the tuning machines. Luckily for me, West Dean college has vibrant Clocks and Metals departments, who have been amazingly helpful to me.
With their help, I’ve come up with a plan!
The tuning machines really have three types of parts:
The delicate ring-shaped heads and worm drive
The worm-gear and post
The frame
Unlike some modern tuners, where the frames are reversed but the gears are all the same, these have clockwise and anti-clockwise worms and worm-gears as well as left and right frames, which ensures that the movement of the head exactly mimics the movement of a tuning peg, except with much more accuracy. These tuners are extremely fine pieces of work - beautifully chased with engraving, held in place by custom screws and as compact and subtle as anything on offer today. The more I study them, the more I admire the 18th Century makers from Dublin.
My first step has been to model everything in 3D CAD (I’m using OnShape which is excellent) and produce engineering drawings of the different component parts. I’m not a CAD expert but I’m rapidly becoming better! Here is a screenshot of the worm-head model.
And here is the post and worm gear (pinion in clock-making terms):
From these I have 3D printed a prototype, both in Resin and PLA to test that it works. This has taught me a lot about worm-gear drives. Making the 3D model parametric has mean I can try out different pitches and angles.
My plan is to cast the worm head and worm itself as one piece. If that isn’t strong enough, then Plan B is to cut the worms on the lathe and cast the heads and then somehow join them.
The worm gear/pinion is going to be cut on a watch-/clock-making lathe, and then the frame I will fabricate from brass stock. At least that is the plan.
I will keep updating the blog as I go - I’m having huge fun learning new things: CAD, 3D printing, clock-making, casting technology, the list seems to be growing by the day!
Many thanks to all the people who are helping me on this, especially Malcolm Archer, Dan Batty, Kate Jennings, and Andrew Braund.