In 18th century England, carpenter and clockmaker John Harrison developed a remarkable method for making wooden clock wheels. These wheels kept their concentricity during large changes in temperature and humidity and had exceptionally strong teeth. Harrison’s use of the particularly oily lignum vitae wood eliminated the need for lubrication, resulting in a longer-lasting and more precise movement. These wooden wheels were just one part of an incredible horological career. Harrison went on to invent the marine chronometer, one of the most important inventions in history, which allowed for accurate navigation at sea. Today in Michigan, clockmaker Rick Hale is carrying on Harrison’s legacy with his spectacular wooden timekeepers.
Hale’s large-scale work eschews traditional tall-case clock architecture, instead adopting a modern style which showcases the inner workings of the movement. These monumental clocks are usually custom-designed to fit a specific space and can take from a few months to a few years to build. Hale’s wheels closely follow the method Harrison developed over 300 years ago and are on full display in his clocks. How are Rick Hale’s wheels made? Let’s have a look.
Step One: Consider The Geometry
“My method of wheel construction allows for radial symmetry, meaning the wheel will “breathe” uniformly in all directions with changes in temperature and humidity. Each tooth is shaped individually from carefully selected stock so that grain direction is identical all the way around the wheel. This layout makes for wheels that remain extremely stable, round, and accurate over time. I also employ the gear tooth geometry John Harrison developed for his sea clocks, and the result – very slender teeth meshing with oversized rollers made from lignum vitae – yields an extremely efficient gear set with incredibly low friction.”
Step Two: Select The Lumber
“Timber selection is paramount to achieving stability. All lumber used for my clocks is kiln-dried and allowed to ‘settle’ at various points in the wheelmaking process. Wheel spokes are generally selected from quarter-sawn lumber and felloes (the perimeter pieces) are plain-sawn. This provides the best possible strength and eliminates weak spots around the edges. Every tooth is individually cut and shaped from very tight- and straight-grained plain-sawn stock for uniform strength and rigidity.”
Step Three: Rough Cut And Trim
“After timber has been selected, each wheel component is rough-cut with a saw and manually trimmed to final dimensions. At that point, all the pieces are ready for joinery. I generally use tongue-and-groove joinery for smaller wheels, and splines for larger ones.”
Step Four: Glue Up
“After the pieces have been glued and clamped together, the wheel blank is trimmed to its final contours, and then the precision work begins.”
Step Five: Bore And Turn
“The only wheels that make it to this stage are the ones that have dead-perfect joinery. These wheels are given a preliminary surfacing, and then their outside diameters and bore diameters are manually turned on a 2000-kg German-made pantograph milling machine paired with an extremely large Swiss-made rotary table. I restored these excellent pieces of machinery myself, and they are dedicated solely to wheelmaking.”
Step Six: Cutting Grooves
“Once the outside diameter and bore are turned, the grooves for the teeth are cut. This is where the 18″ Swiss rotary table really shines, as it allows accurate indexing to a resolution of +/- 1 arc-second (that’s 1/3600 of a degree). Working in wood, that level of precision might seem excessive to some. But when you’re making wheels with 240 teeth at a 34″ diameter, every bit of overkill helps.”
Step Seven: Pressing Teeth
“Teeth are thinned to fit their grooves (a light press-fit that is determined by feel), and they are squeezed into place one at a time using a manual press I fabricated. Traditional hide glue is employed here to fix the teeth securely. After the teeth have all been inserted, the gear is given a final surfacing, and the faces of the teeth are ‘dusted’ for uniformity.”
“In the case of an escape wheel, the teeth are manually inserted in situ on the machine and are contoured to final shape using the pantograph arm and rotary table. This process is time-consuming, but works extremely well.”
Step Eight: Sand, Lacquer, And Mount
“After holes have been drilled and counterbored at the hub of the wheel to attach it to its collet, it’s time for sanding, lacquering, and mounting.”
Wind & Water
Rick Hale’s latest clock is called Wind & Water. Completed in December 2020, this 36″ x 60″ wall-mounted clock has been under development for several years and features a hand-carved frame made from aged cherry, plus daisy wheel motion work, quilted maple hands, stave-style driving weight, and counterweight, and Hale’s signature take on the single-pivot grasshopper escapement. In the tradition of Harrison, Hale used lignum vitae throughout the clock on all rotating parts. The gearing of Wind & Water is based on Harrison’s “chordal pitch” method. Hale works on commission only and is currently developing a lunar phase table clock, which he calls L1.
For more, visit Clockwright.