Author Topic: Great Escapement Clock  (Read 4734 times)

Offline Cedar

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Great Escapement Clock
« on: December 18, 2013, 12:19:52 PM »
I thought other members of the Clock forum may be interested in some pictures of the latest clock from the Cedar clock workshop (my basement).  For some time I have been wanting to design a clock that breaks the clock making rules and makes the escape wheel the dominant feature of the clock, rather than the smallest wheel.  It took me a number of attempts to get to a design that I liked and works.   I now understand why keeping the escape wheel small, to minimize its inertia, is conventional wisdom.

I have put a video of the clock running on youtube at the following link.

http://youtu.be/gaTgut273XI

Richard.

Offline Sablatnic

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Re: Great Escapement Clock
« Reply #1 on: December 19, 2013, 09:52:13 AM »
Like it a lot!

Is it very noisy?

Offline jasc15

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Re: Great Escapement Clock
« Reply #2 on: December 19, 2013, 03:00:38 PM »
Very attractive.  I like the highlighting of the escapement mechanism in the design.  What particular problems did you have with the large escape wheel, since you say you now know why their inertia is typically kept to a minimum.  Seems like it runs fine with a large escape wheel.

Offline Cedar

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Re: Great Escapement Clock
« Reply #3 on: December 22, 2013, 12:38:12 PM »
The clock is no more noisy than my other Graham escapement clocks. It makes a "sturdy" tick-tock, but nothing excessive.

Ideally, you want the escape wheel to have a low moment of inertia (minimize the weight * distance from wheel center) because the escapement stops every time it hits the pallet and then has to be re-started by the force (torque) from the going train.   The higher the inertia of the escape wheel the greater the torque required from the going train. 

The escape wheel in my original design was made from 1/4" ply with a wider rim.  To get the clock to run with a reasonable weight I had to change the escape wheel to 1/8" ply and make the rim as thin as practical.  Originally, I designed the clock to run for 36 hours for a single wind.   However, I had to increase the diameter of the winding wheel to keep the weight sensible and the final design runs for 24 hours.

Offline jasc15

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Re: Great Escapement Clock
« Reply #4 on: December 23, 2013, 08:19:01 AM »
A bit of technical insight to rotational inertia (usually called moment of inertia in engineering parlance):

The moment of inertia of on object can be halved by halving the thickness of the wheel, as Cedar did, but it is more sensitive to the radius (or diameter) than to thickness.  It is related to the square of radius, so a wheel of half the radius will have one fourth the inertia.

Offline Sablatnic

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Re: Great Escapement Clock
« Reply #5 on: December 26, 2013, 03:06:18 AM »
In my opinion the good looks is absolutely worth the cost in higher weight!
I like it a lot!!

Offline steve323

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Re: Great Escapement Clock
« Reply #6 on: December 28, 2013, 09:24:58 AM »
That is a great looking clock.  I agree that the emphasis on the escapement and faster moving gears makes the clock much nicer to look at. 

Can you post a side view showing the spacers and gear stacking.

thanks
Steve

Offline Cedar

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Re: Great Escapement Clock
« Reply #7 on: January 19, 2014, 11:42:32 AM »
Attached is the best photo I could take of the side of the clock.  I hope it helps you understand the sequencing and position of the wheels.

Richard.

Offline steve323

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Re: Great Escapement Clock
« Reply #8 on: January 21, 2014, 12:36:41 PM »
Richard, Thanks for posting the additional picture. 

I like how most of the wheels are way out in front.  Maybe not very practical, but it really lets you see the interaction.

The 1/8" ply for the escapement looks really thin.  It makes sense that it would be required to keep the weight lighter.  I suppose the middle portion could be laminated with an additional thickness to give it more stability and still keep the outer rim lightweight.

Steve