Re: The Impulse Roller & Shape of Pallet

Ian Richardson

Hi All,

To add even further to the confusion, in Shortt's "free pendulum" clock, the impulse arrangement is the other way round!  The pallet (actually the flat surface of a Brocot jewel) rolls over and around the wheel.  It starts "dead" as a tangent to the wheel at the top, and falls down, rotating the wheel, until it drops off.  That has always seemed to me to be a better arrangement which could easily have been incorporated into an otherwise standard Synchronome.  Has anyone ever done that?

Ian R

-----Original Message-----
From: Bepi <pepicima@...>
Sent: Sat, 14 Nov 2020 16:02
Subject: Re: [synchronomeelectricclock] The Impulse Roller & Shape of Pallet

Hal, to minimize the escapement error, in my synchronome it can be made undetectable, you need to carefully center the impulse around the phase corresponding to a vertical pendulum rod. Adding energy when it's all kinetic doesn't change the period in the small angle approximation.
This is why I was looking for a way to mechanically control the phase with precision. Thanks Neville about your answer, I am still looking for a way to do it with better accuracy than by hand, I guess I need to devise a simple process to do it.
I am not claiming it's a needed adjustment for best accuracy, the opposite, I think I reported long ago in this forum that minimizing the escapement error doesn't significantly affect the period in the short turn accuracy, even a large escapement error seems to be very repeatable in a synchronome.

On Nov 14, 2020, at 14:47, H Hal via <haal@...> wrote:

Don't worry Bepi,
I live in a constant state of confusion.
You are impulsing the pendulum at some point during its swing. There are some points (during the swing) that the impulse will be very useful and efficient OR other points where the impulse will be detrimental (the child pushed by dad on the swing gets higher and higher OR gets lower and lower to a stop because it is tea time).
The phase angle represents a point somewhere on that sine curve (which represents the position of the pendulum in time) where impulse may be given.

On 14/11/2020 13:11, Bepi wrote:
Hal, sorry for adding to the confusion, let me make it worse now. In my pseudo-synchronome I control the clock-cycle phase of the impulse by changing a time delay starting from the previous period vertical crossing but it's clearer to speak about a phase angle, as in the angle of the tangent rule, p.-

On Nov 14, 2020, at 13:46, H Hal via <haal@...> wrote:

hi Bepi,

can you explain the difference between phase and time in relation to impulse or are you using the terms interchangeably?


On 14/11/2020 12:42, Bepi wrote:
Ian who are Mr Parsons and Mr Ball and where can I read about their results? I agree that the shape is probably of little importance, more relevant is the location of the impulse in phase/time.
Does anybody know how to regulate the impulse phase in a synchronome in an easy, controllable and accurate way?
The shape might be of some relevance in terms of repeatability which boils down to absence of sharp corners. 



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