An archive case history
By David Walter and Stan Boyatzis – In the World of Horology.
Challenges rarely come any greater or smaller than found in the task of crafting the world’s smallest carriage clock.
Several years ago, I was asked to build a fully functioning carriage clock at the smallest practical scale, preserving its traditional architecture while testing the boundaries of miniaturization.
Design and Layout
A true carriage clock features front and rear plates, four pillars, and the platform with theescapement and balance mounted on top of the plates. With that in mind, I began drafting the mechanism on paper, exploring how compact it could be made without sacrificing performance. I wanted the escapement and balance to be visible (as small as it is) from the front of theclock, I designed the dial, movement and case permitting this. The top of the dialfinishes flush with the platform plate.
Figure 1: The drawing (original concept sketch)
Materials and Assembly
The brass plates are 1.5 mm thick with four turned pillars fixed in place with specially made, black polished, hardened steel screws recessed into both the front and back plates.
I started with 2mm thick brass plates however I decided they look too heavy and chose the slightly thinner brass.
Figure 2: Final 1.5mm plates on the right, with the discarded thicker 2mm plates is shown on the left.
The movement, without its platform, measures:
- Height: 24 mm
- Width: 19 mm
- Depth: 12 mm (including the silver dial)
The gear train configuration is entirely unique to this miniature carriage clock. The barrel
arbor extends through the back plate, while the center wheel sits beneath a custom
“DW-style” cock, my own signature design, combining functional precision with
aesthetic balance. The third and fourth wheels are mounted beneath a separate bridge,
with a dedicated cock controlling the endshake on the fourth wheel that drives the
contrate wheel.
The DW style cock is an original shape I created many years ago for my own clocks and
watches; the jewel is set close to the straight side of the cock while the other side has a
deep scroll curve terminating above the center line of the jewel providing an open view
of the wheel/pinion assembly. The DW style cock is further seen used for the escape
wheel and pallet cocks. These cocks and bridges are finished with matted surface and
beveled edges.
Figure 3: View between the plates, showing the layout of the train
Mechanical Challenges and Innovations
Creating this miniature carriage clock presented numerous challenges, one of the most difficult being the location of the mainspring barrel. To accommodate the barrel it had tobe recessed into the front plate, thus allowing the center wheel to sit far enough forwardto provide sufficient space for the dial and hands.
Another demanding component was the contrate wheel being only 6.93 mm in diameter and comprising 70 teeth. This wheel turns out to be the smallest of its kind ever produced.
For correct train alignment the third and fourth wheels are elevated on sub-bridges, ensuringcorrect meshing through to the center and escape wheels.
Figure 4: The platform under construction.
Constructing the Miniature Carriage Clock Platform
The escapement platform also required careful engineering. Lever escapements need a straight-line layout, with both escape wheel and balance remaining inside a very confined space. Despite the scale, I opted for a 12 mm balance wheel for visual presence andsmooth operation. Traditional balance cocks are too bulky, so I designed a sleek, balance bridge made of steel with tapered arms and a triangular cutout to receive the hairspringstud. A 0.30mm cross hole was drilled and tapped for the stud screw
The train is fully jeweled from the center wheel. The signature is engraved on the backplate while the makers mark is inside the back plate, the winding wheels have been givena “snailed” finish as used by the best watchmakers. Another problem was winding theclock, the traditional square shaft on the barrel arbor would not have been strong enoughand winding may have resulted in the arbor being twisted, bent or worse still broken off.
To solve this, I added a second winding shaft with a square end for the key, mounted with a smaller steel wheel meshing with the ratchet wheel, this shaft has a large pivot inthe back plate and is supported at the outer end by a bridge with a large collar.
Above: The Makers mark. Swan
Another World’s first hallmark peice: a selection of rare materials, uncompromising craft: a tiny all American made piece of horological history”
David Walter
