Adventures in Clock Making
It all started when I was looking for something to amuse myself during the cold winter nights of January 2004, and I came across Jeff Schierenbeck’s Wooden-Gear-Clocks website. The idea of building my own clock seemed like fun, and I purchased a kit of the Ascent Clock. Little did I realize that this would be the starting point of a decade-plus exploration into clock design.
The Ascent clock kit was fun to build, and in no time, I had a working clock hanging in my hallway.
Ascent Clock
However, the clock had a number of limitations that I thought I could improve upon, but I did not have the means of cutting the intricate wooden shapes that I needed to improve on the design. A scroll saw was the answer, and I was soon redesigning and cutting out a new pulley and weight box so that the clock would run for over 24 hours. (I believe that current versions of the Ascent Clock sold by Wooden-Gear-Clocks have been modified to run for over 24 hours).
This initial success led me to look for other wooden clock designs that I could build and learn from. I found Marc Tovar’s Wooden ClockWorks website that sold plans for clocks that could be made using my newly purchased scroll saw. I purchased plans for Mark Tovar’s MLT-2AB wooden clock and set about building it. There is nothing like cutting a 140-tooth wheel (gear) one tooth at a time from a large piece of plywood, knowing that it only takes one slip and you will have to start over again. It greatly improved my scroll saw skills and also my ability to concentrate.
Marc Tovar MLT-2AB Wooden Clock
Building this clock was a great learning experience, and it still hangs on my dining room wall. However, the engineer in me wanted to see if I could improve on the design, and I set out to design my first clock.
To design the clock, I needed a Computer Aided Design (CAD) drafting program. I chose TurboCAD because it had the basic capabilities that I needed at a reasonable price. Next, I needed to understand how to design an escapement mechanism. Mark Headrick’s work “Clock and Watch Escapement Mechanisms” came to the rescue. This is an amazing resource on the design and mechanics of numerous clock and watch escapements. My first clock – Cedar Clock 1 – was heavily influenced by Marc Tovar’s MTL-2AB clock, but the escapement and wheels are all original.
Cedar Clock 1
Cedar Clock 1 was quickly followed by a nearly identical clock – Cedar Clock 2 – that I built, in 2006, as an anniversary present for my parents and now adorns the living room wall in their apartment in London, England.
Cedar Clock 2
Having designed my first clock, I became fascinated with more complicated escapement mechanisms, in particular Harrison’s Grasshopper escapement. I also found the work of Clayton Boyer, a very talented clockmaker from Hawaii who sells plans for a fantastic range of clocks and other interesting mechanisms. I bought the plans for his Bird of Paradise clock that utilizes a Grasshopper escapement. I used the escapement and gear train design from this clock but changed the frame design to create Cedar Clock 3.
Cedar Clock 3
Following Cedar Clock 3, I read extensively about clock design and experimented with a number of clock designs trying to find something that functioned well as a clock and was both statically and kinematically pleasing. Most of these attempts never got beyond prototypes of escapements or gear trains and never became clocks, either because they did not run well or I was not happy with their aesthetics.
In my reading, I came across the Flying Pendulum Clock with one of the craziest pendulum/escapement mechanisms there is. I decided to design my next clock using the flying pendulum. The novelty of spending hours bent over the scroll saw cutting gear teeth had lost its appeal, and chose to use interlocking dowels to create the wheels.
Flying Pendulum Clock
Cedar Clock 4 runs beautifully, and the kinematics of the flying pendulum fascinates everyone who sees it, but as noted in all the literature, it does not keep good time. Even after careful adjustment, it will gain or lose as much as 30 minutes a day. Great as a kinematic sculpture but not as a clock.
As I noted above, I had tired of cutting gear teeth on the scroll saw and started to look for alternatives. Given that I was designing the clocks using CAD software that gives a digital representation of the clock, using this definition to cut the wheels using a Computer Numerical Controlled (CNC) router was a natural next step. After researching the options, I purchased a Zenbot CNC router with a 24” X 16” bed and associate software to generate the tools paths (CUT2D & CUT3D) and control the router (MACH3).
Zenbot CNC Router
Learning to use the Zenbot proved relatively easy, and after some experimentation to determine the best cutting speeds and feeds, the quality of the components is excellent. I have been using the Zenbot to cut clock parts ever since.
In most clocks, the escapement wheel is normally the smallest wheel of the clock. However, it is the wheel that turns the fastest and, to my mind, the kinematically most interesting aspect of the clock. I wanted to build a clock that emphasized the escape wheel by making it the largest wheel in the clock. This was the basis of the “Great Escape Clock,” which was my first clock to take advantage of the capabilities that the Zenbot CNC router had opened up.
Great Escape Clock
It soon became clear why the diameter of the escapement wheels is normally kept as small as possible to minimize the inertia of the wheel. Although I minimized the thickness of the escapement wheel to reduce the inertia of the wheel, it took a considerable weight to keep the clock running, and over time the frame deformed, and the clock stopped running. As much as I liked the aesthetics of this clock when it ran, I decided that I was fighting nature and abandoned developing this design.
In looking for other directions to pursue, I came across what is referred to as the “anniversary” or “400-day” clock that uses a torsional pendulum to regulate the beat. The torsional pendulum met what I was looking for, interesting kinetics and a long oscillation period that allowed me to design a minimalistic gear train.
Torsional Pendulum Clock 1 (2014) was my first clock to use a torsional pendulum and anchor escapement. My objective in this design was to see how “minimalistic” I could make the clock mechanism. To achieve this, the clock uses a “daisy wheel” mechanism for the hour train that connects the minute wheel to the hour wheel, ensuring a 12:1 gear ratio. The daisy wheel is a beautiful mechanism invented by Aaron Dodd Crane, an American clockmaker in the mid-1800s that uses an eccentric drive to drive a daisy-shaped wheel.
Torsional Pendulum Clock 1
I was extremely pleased with how this clock turned out and decided to continue to explore the use of torsional pendulums in future clocks.
Up to this point, I had cut each wheel from a single sheet of Baltic Birch plywood which is very stable and does not warp. Unless one uses a colored wood finish, which can be problematic on the gear teeth, one is also limited to the natural color of Baltic Birch. Cutting each wheel from a single piece of wood also limits the size of the wheel that can be achieved. The solution to this was to develop wheels that are constructed from multiple pieces of wood that are then assembled to form the complete wheel. After some experimentation, I came up with a design that splits the wheel into a central hub, five spokes, and a five-part rim. The mating surfaces are shaped to interlock in a way that ensures accurate positioning.
Torsional Pendulum Clock 2 (2015) is very similar to its predecessor but utilizes a conventional hour train using two wheels rather than a daisy wheel mechanism. The clock wheels, frame, and torsional pendulum weight holder are made from Walnut wood. This clock has been running for over 3 years, and the wheels have remained flat with no evidence that they will warp.
Torsional Pendulum Clock 2
So far, all my clocks had been wall-mounted, driven by a weight that had to be wound up once a day. Because I was running out of wall space in my house for additional wall-mounted clocks, I wanted to branch out to table or mantle clocks. As table clocks do not have the vertical height needed to accommodate the drop of a weight, I decided to explore spring-powered mechanisms. The mechanics of springs turned out to be more complicated than I had expected, so I purchased a number of clock springs from TimeSavers and began to experiment.
I decided to continue exploring using of torsional pendulums and adapted the wall-mounted clock to be spring powered table clock – Torsional Pendulum Table Clock 1.
Torsional Pendulum Table Clock 1
I constructed the winding arbor and the attachment of the spring to the winder shaft using components from the hardware store and hobby shop that were cut, drilled, and soldered together. It worked but was not elegant. Inspired by a colleague at work who had purchased a lathe and was making some interesting items, I bought a small lathe and ancillary equipment from the Little Machine Shop. As a Graduate Trainee at Rolls-Royce approximately 35 years ago, I learned the basics of lathe use. I was amazed at how much came back to me and how quickly I was able to produce small brass and steel components needed to construct a more elegant winder mechanism.
Mini-Lathe
Winder Mechanism Components
Torsional Pendulum Table Clock 2 is almost identical to Torsional Pendulum Table Clock 1 but utilizes lathe-turned components for the winder mechanism. This clock was a birthday present for my sister.
Torsional Pendulum Table Clock 2
More clocks are in development.