Prototype "Harrison - Graham" Escapement

Richard Cedar

NAWCC Member
I thought that members of this forum might be interested in the inception of the latest clock from Cedar Clocks (www.CedarClocks.com). For some time, I have been mesmerized by the motion of the two compound pendulums used on Harrison's H1 clock and have wanted to incorporate them into one of my clocks. Artist friends would describe the movement of the pendulums towards each other before reversing before a collision as creating "visual tension". However, I did not want the complexity of Harrison's Grasshopper escapement.

I recently realized that one could combine the Harrison double compound pendulum with a Graham deadbeat type escapement. (I am sure this is not novel as almost every possible escapement configuration has been explored in the past.) To maintain some sort of symmetry, I decided to split the pallet so that the entrance face is on one side escapement and the exit face on the other. Below is a video of a prototype of the resulting "Harrison-Graham" escapement made from plywood.

This prototype has a 6" diameter escapement wheel with 30 teeth. The pendulum beat is set so that the escapement revolves once per minute. However, I have not decided on the final size of the clock, whether it will be a table or wall clock, or even what I will make it from (walnut wood or acrylic). The next steps are to design the wheel train layout and decide the clock size and type. This is the part of the clock design process I enjoy most, trying to create an attractive configuration, both as a static and kinetic sculpture that also functions as a clock.

Richard Cedar.

bruce linde

NAWCC Member
Donor
nice... i was noticing that there's a lot of additional on the locking faces after locking, which made me think about friction, which made me wonder how this thing is powered? and how long it will run?

Richard Cedar

NAWCC Member
I deliberately designed the pallet with a large locking angle to increase the arc of the pendulum and the visual impact of the pendulums swinging towards each other. I plan to experiment with different pallet face angles as I suspect there is an optimum combination of face and locking angles that maximizes the pallet arc and minimizes friction.

Having had consistent feedback from the galleries where I have displayed my clocks, it appears that customers are put off buying clocks that need winding. Because of this, all my recent clock designs have used electric-powered remontoires. This also gives an additional kinematic element to the clock that I explored in my latest clock.

I plan to do something similar, although not the same, for this clock. The other advantage of an electric remontoire is that one does not need to be paranoid about friction in the wheel train so greatly freeing up constraints on creativity. I used weights on the prototype escapement for simplicity, and so I could measure the torque required to power the escapement.

Richard Cedar.

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tok-tokkie

Registered User
That is a great idea = Harrison & Graham. Using an electric remontoire to escape the tyranny of a drive train and concentrate on the visual & kinematic interest of your designs is both practical and appropriate. As you state "kinetic sculpture".

Richard Cedar

NAWCC Member
Tok-Tokkie - Thanks. “Escaping the tyranny of the drive train” would be a great title for a book on clock design.

Phil Burman

Registered User

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