Devon Sea Clock Experiences and Modifications

clockmaking, sea clock
Devon Sea Clock

Having spent some time on the Devon Sea Clock the following notes might help anyone trying to work on the grasshopper escapement.

What struck me as a potential issue was the lack of repeatability of the curly whirly leaf springs used to activate the grasshopper pallets.   As the clock arrived with me, these two springs were far from identical in their shape. This worried me but I stuck with them initially.

Devon Sea Clock showing original spring arrangement.

After spending many hours I finally got the clock running but the springs still did not feel like they were a good solution.

I stripped down the centre bosses and began to consider the idea of replacing the spring with simple compression springs.  Fusion 360 was calling.

I created an infill plastic boss to sit between the two brass plates of the centre boss.   The two bosses are identical.   The insert sat over the internal spacer pillars the central post.   I then put two M3 holes through the boss to allow an adjuster screw and a small compression spring to fit in each and act against the pallet ends.

Difficult to explain so here are some pictures.

 

Devon Sea Clock Centre Boss
Devon Sea Clock with centre boss cover removed showing how the spring act on both ends of the pallet.  The pallet hinges around an arbor pin which you can just see near the cylindrical brass rod. (This is a small counterweight to allow pallet weighting).
Devon Sea Clock new boss
Fusion 360 insert that sits between the two brass discs of the centre boss. Note that the pillar holding the original spring has been removed. The boss sites on the plate in the same orientation as the image above. The two lower holes in the front face take small compression springs with screw tensioners.   Note the wide wedge is to allow access to the grub screw adjustment.   The larger of the top three holes allows access to the rotation orientation adjustment screw.
Devon Sea Clock new boss view 2
Devon Sea Clock boss from other side showing the two spring holes.  The springs are from an old RS spring kit and are 2.5mm diameter in 0.25mm wire.

So far it seems to work and I am slowly bringing it on time with the Microset Timer.

Update – Clock now running pretty much to time and is keeping to a few seconds per day.   Really pleased with the outcome.  Microset is a wonderful piece of kit that lets you see all that is going on with a movement.