Beat Error and Positional Error

[canthus]

Assuming the hairspring is sitting correctly in the regulator pins, is flat, correctly coiled and clean.  The balance has been correctly lubed and pivots/jewels are all ok, and it is poised ok.  The timegrapher is set correctly for lift angle, beat rate etc   .I appreciate that the quality of the movement and lack of wear etc are important but assume that these are at acceptable levels.

What effect will beat error have, if any, on the positional timing?   Is there a target beat error range that should be aimed at for good positional error?

Your esteemed comments would be much appreciated.

 

 

[rodabod]

Should not affect it noticeably. Realistically I'd aim for <2mS but <1mS is excellent. 

[praezis]

dito, both are not connected.

Beat error is a big topic in communities, but is highly overestimated, it has little to no influence on the performannce.

If displayed as "ms" like with most TMs, this value is a vague indicator only: the identical beat error (i.e. the angle that the balance impulse jewel is off the middle line, with no mainspring power applied) will show different "ms" values, depending on 1) beat rate and 2) amplitude.

So you can say ">1ms is bad, <1ms is fine", but it is nonsense without stating amplitude and beat rate, which nobody does. The only exact value is beat error in degrees!

Frank

 

 

[rodabod]

Frank is right, I should have maybe mentioned that I almost always work with 18000bph watches. It's still handy to have a ballpark figure for what sounds reasonable. For example, if you are getting a reading of 9mS then it's probably advisable to adjust. I would only make any adjustments when the amplitude is healthy.

[canthus]

Thanks folks,  Had 9.9ms !!!!  Got it down to 4ms. Better but still messing about with it. Probably wreck the h/spring in the process!!!

[jdrichard]

  On 6/29/2017 at 8:41 PM, rodabod said:

Should not affect it noticeably. Realistically I'd aim for <2mS but <1mS is excellent. 

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I have serviced an Elgin Veritas and have the amplitude at 270 and the beat error 1.9ms. Watch is gaining 5seconds per day face up, and over a 3 day period is off maybe 7 seconds. Not sure if I want to mess with the beat error? 

 

Edited December 15, 2020 by jdrichard
Inaccurate

[rodabod]

I wouldn’t adjust that already-low value if it were me. I doubt it would achieve much if anything noticeable. 
 

I should really have been less vague when I made that statement about values in milliseconds as of course, that figure varies proportionally with beat rate - so you’d expect a lower value on higher beat rates. About 90% of the watches I work on are 18,000bph. 

[Watchfixr]

  On 12/15/2020 at 2:30 PM, jdrichard said:

I have serviced an Elgin Veritas and have the amplitude at 270 and the beat error 1.9ms. Watch is gaining 5seconds per day face up, and over a 3 day period is off maybe 7 seconds. Not sure if I want to mess with the beat error? 

 

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Ship it! Beat error in that range will not hurt anything.

[JohnC]

  On 12/15/2020 at 2:30 PM, jdrichard said:

I have serviced an Elgin Veritas and have the amplitude at 270 and the beat error 1.9ms. Watch is gaining 5seconds per day face up, and over a 3 day period is off maybe 7 seconds. Not sure if I want to mess with the beat error? 

 

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I am no expert but I feel that if you have that much amplitude you're basically done with the beat error. Now if the watch is varying by 200 seconds when you put it vertical, then maybe focus on the shape and poise of the hairspring. But if all that's okay, then no, resist the temptation!