Computer Aided Design of Grasshopper Escapement Geometries

[glathoppa]

http://soptera.wordpress.com (go to 'DOWNLOADS') includes PDF files explaining how single pivot, twin pivot and twin balance grasshopper escapement geometries may be created using Computer Aided Design (CAD) techniques.

Any realistic designer choices can be incorporated, although you should ideally stick to Harrison's choices (they're all defined in the text). End/start ratios of 1:1 are a big no-no, according to Harrison.

You'll need to learn basic CAD (great fun, IMHO) and high precision demands the creation of a fair number of geometries. Turbocad 15 software (for example) is very cheap and is apparently perfectly adequate.

Cheers!


Edited 13th October 2013 to revise link to files.

[steve323]

Welcome to the forum glathoppa.  And thank you for posting some interesting links.  I have never seen the double pivot grasshopper escapement before.

There is not too much activity on this forum (if you exclude the obvious spam).  Maybe I will find some time to make some progress on my clock someday. 

Steve

[glathoppa]

The following links to beautiful animations of Harrison compliant grasshopper escapements should be of interest and value:

Single pivot Harrison compliant grasshopper escapement: https://www.youtube.com/watch?v=7TBWJC0HYRE

Twin pivot Harrison compliant grasshopper escapement: https://www.youtube.com/watch?v=swGGflJd71I

The comments section of each video may be read in full, by left clicking 'SHOW MORE', located a few lines below each video.

Both of Ken Kuo's animations and the mechanical designs are entirely based upon the geometries illustrated and created in the 'Downloads' section at http://soptera.wordpress.com (please see my opening post, above). Both geometries therefore comply exactly with Harrison's final intentions, recorded close to the time of his death (i.e. in his 1776 manuscript 'Concerning Such Mechanism...' and an apparently associated, contemporary illustration, currently catalogued as 'MS3972/3' in The Worshipful Company of Clockmakers library).

Should any links fail or become out of date (as they all too often seem to do), please visit www.youtube.com and search for username 'Ken Kuo'. Then search within Ken Kuo's videos for 'One Pivot Grasshopper Escapement - John Harrison' and 'Two Pivot Grasshopper Escapement - John Harrison'. Please note that similar versions with similar titles amongst Ken Kuo's videos fail to incorporate visible recoil and are, therefore, less informative.

[glathoppa]

In addition to my previous post, the following Ken Kuo animation should also be of interest and value:

Unilateral twin pivot Harrison compliant grasshopper escapement: https://www.youtube.com/watch?v=fBfp9riiJxc

All currently known written, illustrated and/or physical evidence attributable to John Harrison indicates that he invented and constructed three configurations of the grasshopper escapement: the twin pivot, the single pivot and the twin balance. There is, however, currently no written, illustrated or physical evidence that Harrison ever identified, recorded or constructed a fourth configuration, which will be referred to as the ‘unilateral twin pivot’ or ‘UTP’ grasshopper escapement.

Ken Kuo's geometry, but not the entirety of the mechanical arrangement, are based upon the description in the 'Downloads' section at http://soptera.wordpress.com (please see my opening post, above). This geometry therefore complies exactly with Harrison's final intentions, recorded close to the time of his death (i.e. in his 1776 manuscript 'Concerning Such Mechanism...' and an apparently associated, contemporary illustration, currently catalogued as 'MS3972/3' in The Worshipful Company of Clockmakers library).

The comments section of this video may be read in full, by left clicking 'SHOW MORE', located a few lines below each video.

To avoid misunderstandings, please note my comment re pallet nib bounce, which is unnecessarily excessive in the video.

My response to misleading comments by 'KEvronista' should also be read in full by left clicking 'View all 3 replies' below his first post. KEvronista eventually acknowledges his error, although I do worry that some observers will be lead astray if they don't read the entire exchange.

Should the link fail or become out of date (as they all too often seem to do), please visit www.youtube.com and search for username 'Ken Kuo'. Then search within Ken Kuo's videos for 'Unilateral Twin Pivot Grasshopper Escapement (UTP Grasshopper Escapement)'.