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Winding > Power > No Friction > Wheels n' pinions > Grasshopper > Pendulum > Grid Iron > Balance Springs > Time

H1 Sea clock winding

Winding the Clock

The Sinclair Harding H1, unlike the original, is designed to be a practical piece and needs to be wound every 7 days, it will in fact go for nearly 8. A substantial cranked key winds the Fusee through a 2:1 step down gear ratio making the once a week experience almost effortless.



H1 Sea Clock spring barrel


The power to drive the H1 is provided by 2 springs housed in barrels. The right hand larger barrel shown in the opposite picture, around which the cable is wound is empty and the spring is actually housed in the left hand smaller barrel. The cable drives a 2 start Fusee, carefully matched to the two springs and in order to ensure the escapement continues to operate while winding, maintaining power is provided to the Fusee Assembly.


H1 Sea Clock rollers

No Friction!

John Harrison was very clever and wanted to avoid using lubrication wherever possible. The arbors around which the springs are wound are mounted on rollers. On the Sinclair Harding H1, these rollers are positioned on the outside of the plates and if viewed carefully and be seen rotating very slowly.


H1 Sea Clock wheels and pinions

Wheels N' Pinions

Harrison used wooden wheels and pinions throughout, using the Lignum Vitii, a wood which exudes its own oils. On the Sinclair Harding model, the wheels and pinions were purposely made in brass and polished steel. The interaction provide a fascinating spectacle and reflections from the plates and highly polished wheels serve only to deceive the observer.


Grasshopper escapement


At the top of the train and on view from the front is John Harrison's famous Grasshopper Escapement. Designed to have no sliding surfaces (and hence no lubricant) watch how the escape wheel impulses the pallets which then gently let go the wheel when the opposite pallet engages.


Distinctive in their shape and linked together, the Sinclair Harding Pendulums are made of Invar - a material with a low Coefficient of Thermal expansion and not available in Harrison's day - what luxury!. The Pendulums arbors are mounted at each end on what are small segments of very large rollers, which form a small Vee. This arrangement needs no lubrication and results in minimal friction.

The length of each rod, combined with the massive Bobs and the balance springs ensure that the whole assembly oscillates every 2 seconds. The counterpoised oscillation ensures that the rolling motion of a ship would have equal and opposite effects on each pendulum with a nett effect of - zero. > Below you can see the links between the two pendulum assemblies


H1 Sea Clock balance springs

Grid Iron
On H1, Harrison used a complicated Grid Iron system, which constantly adjusts the length of the springs as the temperature varies.

The three gridirons are fixed to the central plate, the central gridiron shortens as the temperature increases and the bottom and top gridirons lengthen. The assemblies are linked together by a complex toggle and the lever system, which effectively magnifies the individual movements of each gridiron.


Balance Springs
The 4 matched balance springs are connected to the Pendulum rod frame and to a central column mounted to the back plate. The springs are made from high-grade spring steel, formed into shape and heat-treated to maintain the springs shape. The 4 springs have to be matched to ensure the pendulum system performs perfectly.

To the left shows the top central plunger, which moves forwards and backwards as the temperature varies which in turn, adjusts two pads, against which the balance spring acts.

One can only admire the genius of John Harrison, however it is hardly surprising that after Sea trials Harrison found that the system was not responsive enough and H2 he designed a device, which we now know as the Bi-metal Strip.


H1 Sea Clock dial

And now to tell the Time.
The chapter rings are as near to the original we could get. Made in brass then hand engraved, wax filled, grained, silvered and finally lacquered to prevent tarnishing. The dial requires careful study. The top seconds hand is connected directly to the Escape wheel, watch carefully as it moves each second, gently recoiling to allow release of the escapement pallets. Each revolution is equal to 2 minutes. The minute hand and Hour hand dials are equal to 2 Hours and 24 hours per revolution and finally – just in case you have been at Sea for many days, a calendar wheel indexing each ½ day.

We hope you have enjoyed looking at the detail of our H1, we specialise in producing clocks finished to the highest standard and with a great attention to detail. Almost every part is made in our workshop and almost every non-moving part is Gold plated to ensure the glittering spectacle remains indefinitely.

The first piece was mounted on a Granite base, which can be gently rotated, and the whole is protected by an impressive brass framed glass shade.

We like to encourage input into the design and so the base and style of case are yours to decide upon.

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