John Harrison's H1 Replica by Sinclair Harding

This is English master clockmaker Sinclair Harding's H1 Sea Clock, 3/4 the size of the original but no less impressive. This is a remarkable timepiece that enables us to take a closer look at how Harrison managed to create such an incredible device. In this machine, Sinclair Harding have incorporated the major inventions of Harrison, including the roller mounting of the Spring barrel arbor, the Grasshopper escapement and beautifully recreated the complexity of the Grid Iron compensation mechanism.

This beauty took 5 years to create and is testament to the skill and patience that the company puts into all its clocks. Here we see the winding mechanism for H1, a pleasure that has to be carried out once every 7 days or so. The clock will actually run for nearly 8 days but it’s good to get into a routine when winding any clock, so 7 days is a good compromise. Winding the clock is made easier by the step-down mechanism that uses a ratio of 2:1, making winding extremely easy.

H1 winding Key

Two springs housed in barrels provide the power for H1. A 2 start fusee ( A cone-shaped pulley with a spiral groove, as the spring loses power the cone shape distributes the power evenly ) is carefully matched to the springs. Maintaining Power is also provided to the fusee to keep the clock running during winding.

H1 Spring Barrel

During the course of creating his series of sea clocks, Harrison invented the roller bearing to keep friction to an absolute minimum, and also to avoid the use of dirt and dust attracting oils. Sinclair Harding's H1 includes the use of bearings on the outside of plates which can be seen turning as the power winds down.

H1 Rollers

One major difference between the original H1 and Sinclair Harding's H1 is the use of brass and polished steel wheels and pinions in the latest example. Harrison made extensive use of a specific type of wood; Lignum Vitii, which was used by Harrison because it contains a natural oil lubricant that makes it ideal for creating frictionless (or near frictionless) bearings.

H1 Wheels & Pinions

The grasshopper escapement is so called because of the unique movement of the pallets after the escape wheel has impacted and released them. The movement is said to be similar to that of the back legs of the grasshopper. Whatever the reason for the name, the action is a fascinating one that can be clearly seen operating within the mechanism of this clock.

H1 Grasshopper Escapement

Sinclair has used some materials that were not available in Harrison's time. One such material is Invar, invented in 1896 by a Swiss, Charles Edouard Guillaume. Invar is an alloy of Iron and Nickel with small traces of carbon and chromium. Its most important property is its low coefficient of expansion, making it an ideal material from which to make the pendulums as seen below. In order to keep friction to a minimum, the pendulums are mounted on large rollers which require no lubrication.

H1 Pendulums

H1 certainly looks strange and unlike any other clock, but there is a very good reason. For use at sea a mechanism had to be invented whereby the rolling action of the ship could be counteracted by movements in any pendulum used. By incorporating two pendulums each moving opposite to the other, Harrison created a mechanism that was not affected by movements of the ship allowing accurate time to be maintained. This original feature is reproduced in Sinclair Harding's H1, probably the most fascinating part of the clock as seen from different angles in the pictures below.

H1 Pendulums Arbors mounted on very large bearings

The huge springs used in the original H1 have been incorporated in the Sinclair Harding model, along with the complex grid iron system that adjusts the length of the springs as the temperature rises and falls. Linked by a complex system of toggles and levers, the system ensures constant timekeeping at most temperatures.

H1 Grid iron Mechanism

In order for the entire counter-balancing pendulum system to operate effectively, each of the four springs have to be exactly matched. The springs are made from high-grade spring steel and go through a process of heat treatment and pre-stressing in order to maintain an exact shape.

H1 Springs

H1 Compensation Mechanism

The fascination for most watch or clock collectors is not only how an item looks, but also how it works. Sinclair Harding have not only managed to produce a most magnificent recreation of probably the most important timepiece ever created, but have also made it an item of sheer beauty. To be able to see the workings of any timepiece is a delight in itself, but to see this one in action stirs the emotions, after all Harrison created this masterpiece back in 1775 without all the modern equipment and knowledge we now have.

H1 Dials

The final touches to this timepiece are almost exact to the original design and I'm sure Harrison himself would be proud to see this recreation. The chapter rings are brass, hand engraved, filled with wax, grained then silvered and lacquered for protection.

H1 Sea Clock Dials

This is a wonderful timepiece. There's only one thing wrong with it - I can't afford one!

H1 Sea Clock from Sinclair Harding

See this and many other fine timepieces at Sinclair Harding's Website

All images copyright Sinclair Harding. Reproduced with permission.

Other Pages of Interest

Sinclair Harding's H1 Top

Read about John Harrison & the Longitude Problem

The Ball Pocket Watch Co

The Elgin Pocket Watch Co

The Hamilton Pocket Watch Co

The Hampden Pocket Watch Co

The Illinois Pocket Watch Co

The Ingersoll Watch Company

The Howard Pocket Watch Company

Waltham Pocket Watch