Author Topic: Rabbit's Strutt clock  (Read 10610 times)

Offline millerdlca

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Rabbit's Strutt clock
« on: August 06, 2006, 03:06:25 PM »
Rabbit, on your web site you have a wooden William Strutt epicyclic clock which has piqued my interest. I've done some research and have obtained a couple of photos from a book in the library and am ordering the W R Smith book on building a brass version.

I was wondering what sources you used in designing and building yours and whether you used any published plans or developed your own.  I haven't found anything useful on the Interent as yet.

Thanks,
Dennis

Offline rabbit

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    • http://flashpages.prodigy.net/rpirtle/index.html
Strutt Epicyclic
« Reply #1 on: August 09, 2006, 08:16:42 AM »
thanks, Dennis.
i designed my own.  i figured out how it was supposed to work from a copy of a copy of a copy of a practically un-readable diagram. (a copy is attached with my tooth counts written on it).
From what i understand, the tooth counts for the brass version are probably unrealistic for a wooden piece.
If you try to make a layout of this gear train, you'll discover one of its mysteries: the meshing gears are not of exactly the same pitch! For example the 36 & 33 tooth gears of the "dial train" have the same pitch diameter; and the 30t meshing with the internal 64t are not even close to the same pitch. This sounds unfeasible, but the tooth shapes make up the secret.
My train has a 35.2 rev/hr escape which leads to about a 1 1/4 seconds pendulum with the 40t escape. (also quite odd, huh?) Mine has a "shortie" compound.
i just love this mechanical marvel because it's so complex and yet at the same time so simple. The simplicity of this train is partly why it's so efficient.
i still don't have a camera, so the pics on my website are all i have.
- rabbit

Offline millerdlca

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Struut Epicyclic
« Reply #2 on: August 09, 2006, 10:14:01 PM »
Thanks for the information Rabbit.  I had come across that image in my research (it is supposed to be from the book British Skeleton Clocks) but I couldn't really make out the tooth counts.  I've tried to track down a copy but it seems to be an uncommon book, at least around here (did a search through our provincial network of 265 libraries).  

I did find a similar book called Skeleton Clocks that describes the movement and gives the tooth counts but no diagrams, so it's a little difficult to follow what they are describing.  Your tooth counts will be most useful.

As for the W.R. Smith's version, I didn't really expect that the brass tooth counts would be directly usable as they are probably much too small.  I'm more interested in the information it will provide on the way it works and is put together.  The write-up for his book mentions the use of a Ferguson's Paradox in the gearing, which would be the ones you mentioned that mesh with differing pitches. I've looked up some information on the Ferguson's Paradox and I think maybe I'll need to make a model of one to understand how it works - my mind cramps trying to vsiualize the movement.

Dennis

Dave

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Rabbit's Strutt clock
« Reply #3 on: August 10, 2006, 12:51:07 PM »
Hi Dennis, i have plans for a Strutt type clock but the one by Bill Smith goes into more detail. If i remember correctly, Bills research found that the original clocks had depthing probs and he modified the gearing in his book. If you give me a call at creedclocks(at)hotmail.com i will scan what you need, just ask, regards Dave

Offline millerdlca

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Strutt clock
« Reply #4 on: August 11, 2006, 08:37:05 PM »
Thanks Dave, that would be great.  It will be interesting to see what differences there are between your version and the Bill Smith version.  I'll send you an e-mail off-list.

Dennis

SCAR

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Strutt clock
« Reply #5 on: August 29, 2006, 09:38:32 AM »
I've tried to diagram the Strutt train as I can figure it from the posts and Rabbit's photos.  I also tried to transcribe the text in the image as best I could.

My calculations based on the diagram seem to jibe with Rabbit's work and the image.  If interested, I can post these.

SCAR

image text:

Figure 4 [...]An exploded view of the clock.  The center pinion (A) of eight leaves is directly driven from the fusee wheel and carries on it an annular ring (B) freely mounted.  The outside diameter of this ring is cut with 168 teeth meshing directly with the escape pinion of six whose arbor (C) carries a 'scape wheel of thirty-four.  Pinned to the center arbor and mounted directly in front of the annular ring is a counterpoised carrier (D) which carries a single planet wheel (E) of sixty-eight.  This meshes with the 144 inner teeth of the annulus.  The planet wheel in turn carries a pinion of eight.  Meshing with this pinion are two solar wheels (F) and (G).  The wheel (G) of sixty-six is screwed through a spacer directly to the fixed center spider of the dial, thus providing the stationary [...] member of the epicyclic train.  The wheel (F) of seventy-two runs freely on the center arbor [...] extended pipe carrying the hour hand.  The setting of the hands on such a clock must be carried out independently as each is mounted with [...] friction [...].

The train is calculated as follows:

The center arbor rotates once per hour as also does the carrier.  The planet wheel rotates 8.25 per hour and the hour wheel (F) is driven forwards six teeth per hour and, therefore, rotates once in twelve hours.  Applying epicyclic calculations, the planet wheel drives the annular ring [...] (i.e., [sic]clockwise) 3.8958 per hour by its own rotation.  However, in one hour the carrier has completed one revolution and this must be added to the work done by the planet wheel, therefore, the annulus rotates 4.8958 per hour.  This action, therefore, drives the 'scape arbor anticlockwise 137.083 per hour (i.e., 2.2847 per minute or 155.36 beats per minute) necessitating a pendulum length of 5.8 in (14.8 cm).