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I am encouraged
I think I will have another try at Brian Law's Grasshopper escapement.
I made the parts a while ago but I could not get close to making it work.
With my new found knowledge, experience and success I hope to succeed.
Here goes ...
Where to start ...
Where to start ...
- Recheck the parts I have made
- Understand (not worry about) the features that are not specified
- find the main / significant movement points and analyse
- be prepared to adjust (12" rasp) the parts to suit
For example:
This is my starting point
Preparatory Analysis
Preparatory Analysis
I don't know where to start ...
In the gravity escapement there was an obvious rest (no movement) position that that I could use as a starting point.
There is no position like that for the grasshopper escapement - all parts are always moving.
My initial approach in these situations is to position the pallets (in this case the escapement arm) horizontally when the pendulum is vertical.
But, what is "horizontal" ? For example, in the above diagram I have "designed" the GH-RH Arm horizontally, but Brian Law has designed it not horizontally.
So, What to do?
So, What to do?
I am going to start twice - at the extremities of the pendulum swings (at rest for an instant ? ) and work in from there and hope that I meet in the middle with understanding.
Pendulum at far right
Pendulum at far right
There is a problem (as a colleague of mine used to say with a wonderful Greek accent - probably with one finger raised) ...
How far does the pendulum swing? What is "right"?
- So I was still using smoke and mirrors.
To start outside and work in I first need to start inside and work out? Think about it - you know what I mean.
I took a closer look at Brian Laws' diagrams and videos - and the starting point (above)
- When the pendulum is swinging right - the pallets (escapement arm (green) ) turn anti-clockwise
- This pushes the GH-LH Arm (red) anti-clockwise
- At some stage the GH-LH Arm (red) is in a position which "correctly" locks the escape wheel
- The GH-RH (blue) Arm touches the escapement arm (green) because of the balance weight and gravity but that is not important right now.
I estimated this position from diagrams.
I measured the angle and it came out a bit more than 5 degrees.
So, Pendulum at far right I chose to be 5 degrees from the vertical.
Note that the "horizontal" at mid-pendulum swing still has no independent meaning - it depends on how the part was "designed" and what you mean by "horizontal".
But, I think I have found one of my starting points.
Of course, one must remember the RULES.
Pendulum at far left
Pendulum at far left
Using similar logic ...
- When the pendulum is swinging left - the pallets (escapement arm (green) ) turn clockwise
- This pushes the GH-RH Arm (blue) clockwise
- At some stage the GH-RH Arm (blue) is in a position which "correctly" locks the escape wheel
- The GH-LH (red) Arm touches the escapement arm (green) because of the balance weight and gravity but that is not important right now.
I could measure the angle but it should be about the same and even if it is not then the other things are wrong (need adjusting) not the angle. The pendulum swings evenly.
So, Pendulum at far left I chose to be 5 degrees from the vertical.
A Note: The right-side diagram (above) looks OK. But the left-side diagram (at right) looks like it could be better - lengthen the stopping extrude on the arm (blue); or lengthen the pushing extrude on the escapement arm (green) so that it pushes the arm (blue) a bit more. We'll see.
Of course, one must remember the RULES.
So, there I have it - my starting point(s) ...
So, there I have it - my starting point(s) ...
... far right and far left
And, just by chance (because I had to work backwards (sideways?) ) the positions of the other parts thanks to gravity and inertia (? push).
So, will it work? ... Not as such --->
But what can I say? - to be helpful, I mean?
- the red stopper extrusion seems to go too far in
- the red stopper extrusion seems to hit the point of the tooth
- the red stopper does not get released
- the blue arm interferes with the red arm maybe it wouldn't if the red arm escaped)
- the blue stopper extrusion seems a bit short
Anything good ?
- the blue extrusion does seem to stop and release the escape wheel (and would again if the blue arm was released?)
- the red arm gets a lift away from the green arm (that's the "grasshopper hop", I think?)
Time passes ... Time passed ... Times past ...
Time passes ... Time passed ... Times past ...
I have tried lots of things - adjusting shapes, lengths, balance weights, turning pressure on the escape wheel - it "works" differently to the above but no better.
Most of the time the stopper stops but does not get released (escapes)
In the gravity escapement (times past) I had the same problem(s) - the arm slipped when it shouldn't or would not escape. I solved it (?) by adjusting shapes and drops and it all seems to be good.
So, back to basics ?
Let's assume ...
Let's assume ...
... that Brian Law's specifications are correct; and
... that I have followed the correctly (see RULES)
Of all the apparent problems, what can I adjust without changing the design?
In the past I have been at pains to have no recoil in my escapements because I think it is bad, however
I have had a rest and another look at the video ...
If I look very closely for a long time with lots of pause / plays I think I can see recoil. Is this bad? Is this good? Was it expected? planned?
So, another epiphany (I think) --- the recoil is planned, good and is what allows the arm(s) to escape.
So, here I am starting again at my starting point
So, here I am starting again at my starting point
Let's examine the model and see if / how recoil can happen.
Time passes ...
I haven't done much. I have been thinking a lot, and relooking at Brian Laws' diagrams and video; and checking my construction details - it all looks OK to me.
As a last resort I decided to ask the whole wide world in general.
I asked "How does the grasshopper escapement work?".
After sifting through all the offers to escape to great holiday destinations and offers from attractive single women to go out with me ...
... I received a reply from Guy D. Aydlett.
He was helpful and encouraging - I am on the right track.
So, here I am starting again at my starting point
So, here I am starting again at my starting point
Let's examine the model and see if / how recoil can happen
... time passes ...
... time passes ...
... time's passing ...
... time passes ..
... time's passed ...
( ... time's past ... )
Imagine, if you will, Clint Eastwood in the paper bag.
:-)
It's not working :-(
I am loath to change anything form Brian Law's instructions because his clocks work.
Of course, I have changed heaps of things like angles, length, teeth shape, pendulum swing angles ... all to not avail ... or at least, I am not prepared to present animations which are better but just show that I don't know what I am doing.
I think I'll go on a long walk
Grasshopper0001 Guy Adylett.pdfGoogle Sites
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