Pendulum clock runs *fast* in hot weather

[NY]

We have a very old pendulum grandfather clock - the pendulum is probably
about 2 feet long with a slow tick. I've noticed that in the hot weather,
when it's probably been warmer inside the house than normal, the clock is
running *fast*. I would expect it to run slow, since the pendulum will
lengthen slightly in the warmer temperature and

t = 2 pi sqrt (l/g)

as l increases, so does the time period t between ticks

The pendulum is a single rod, not a multi-bar rod with two different metals
so as to compensate for thermal expansion.

[T i m]

On Fri, 3 Aug 2018 09:30:30 +0100, "NY" <m...@privacy.net> wrote:

>We have a very old pendulum grandfather clock - the pendulum is probably
>about 2 feet long with a slow tick. I've noticed that in the hot weather,
>when it's probably been warmer inside the house than normal, the clock is
>running *fast*. I would expect it to run slow, since the pendulum will
>lengthen slightly in the warmer temperature

<snip>

Lower viscosity of the lubrication on the lighter / faster moving bits
= less drag?

Cheers, T i m

[newshound]

My thought too. I wonder if it is a "spring" one rather than having
traditional weights. Whilst the spring unwinds very slowly, there's a
lot of area in contact with a very thin film of often rather thick,
sticky oil. If I had a bit more time I'd have a look at what temperature
does to the viscosity of air, which is also slowing the pendulum.

[Graham.]

Not according to Mr Newton.

--

Graham.
%Profound_observation%

[GB]

On 03/08/2018 09:30, NY wrote:

> The pendulum is a single rod, not a multi-bar rod with two different
> metals so as to compensate for thermal expansion.

I'd have another, really, really close look at that pendulum. The
thermal compensation mechanism may not be that obvious.

[NY]

"newshound" <news...@stevejqr.plus.com> wrote in message
news:f7OdnRqkgYULhvnG...@brightview.co.uk...

> On 03/08/2018 10:00, T i m wrote:
>> On Fri, 3 Aug 2018 09:30:30 +0100, "NY" <m...@privacy.net> wrote:
>>
>>> We have a very old pendulum grandfather clock - the pendulum is probably
>>> about 2 feet long with a slow tick. I've noticed that in the hot
>>> weather,
>>> when it's probably been warmer inside the house than normal, the clock
>>> is
>>> running *fast*. I would expect it to run slow, since the pendulum will
>>> lengthen slightly in the warmer temperature
>>
>> <snip>
>>
>> Lower viscosity of the lubrication on the lighter / faster moving bits
>> = less drag?
>

> My thought too. I wonder if it is a "spring" one rather than having
> traditional weights. Whilst the spring unwinds very slowly, there's a lot
> of area in contact with a very thin film of often rather thick, sticky
> oil. If I had a bit more time I'd have a look at what temperature does to
> the viscosity of air, which is also slowing the pendulum.

Sorry, I should have said. It uses weights rather than a spring. Bloody
nuisance having to remember to wind it every morning :-)

Would viscosity of lubrication oil and air around the pendulum affect the
timing of the pendulum? I can imagine them causing more energy to be lost as
heat.

[newshound]

If the pendulum is hung from a flexure pivot, then lubricant doesn't
affect the "free" period of the pendulum, but the escapement does give
it a little "push" (after all, it has to supply some energy to overcome
air resistance). So less friction in the drive mechanism may give you
slightly more "push".

Engineering Toolbox shows both dynamic and kinetic viscosity of air
increasing with temperature, which is not what I was initially
expecting. On reflection, though, that is right. It's been a long time
since I thought about kinetic theory.

https://en.wikipedia.org/wiki/Kinetic_theory_of_gases

[newshound]

Both weights and a spring are still providing a "push" to the
escapement, so could be affected by lubrication.

Viscosity of air goes up rather than down with temperature. Damn.

[charles]

In article <pk179j$vs8$2...@dont-email.me>,

I have a 1903 bracket clock with pendulaum. It is NOT a temperature
compensated one.

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

[T i m]

On Fri, 3 Aug 2018 10:30:04 +0100, "NY" <m...@privacy.net> wrote:

<snip>

>Would viscosity of lubrication oil and air around the pendulum affect the
>timing of the pendulum?

No, but the viscosity of the oil might impact the running of the
escarpment etc?

Cheers, T i m

[T i m]

On Fri, 3 Aug 2018 10:38:15 +0100, newshound
<news...@stevejqr.plus.com> wrote:

<snip>

>Viscosity of air goes up rather than down with temperature. Damn.

;-)

Cheers, T i m

[T i m]

And the escapement. ;-)

Cheers, T i m

[Clive Page]

On 03/08/2018 10:00, T i m wrote:
>

> Lower viscosity of the lubrication on the lighter / faster moving bits
> = less drag?

We have a similar pendulum clock and see that it also runs a bit fast in this weather. My guess was also that it was the lower viscosity of the oil, or perhaps lower air drag on the pendulum.


--
Clive Page

[John Entwistle]

How is the pendulum bob fixed to the rod? I have a 1900-ish pendulum
clock whose flat circular bob is supported at its bottom. So as the
temperature rises the bob's center of gravity moves upwards and tends to
compensate for expansion of the rod downwards. The clock keeps excellent
time, within 5 seconds per day when compared with a radio-controlled
clock. This is despite its pendulum rod being made of wood which I would
expect to be affected by atmospheric humidity, but it doesn't seem to be.

---
This email has been checked for viruses by AVG.
https://www.avg.com

[GB]

On 03/08/2018 10:51, charles wrote:
> In article <pk179j$vs8$2...@dont-email.me>,
> GB <NOTso...@microsoft.com> wrote:
>> On 03/08/2018 09:30, NY wrote:
>
>>> The pendulum is a single rod, not a multi-bar rod with two different
>>> metals so as to compensate for thermal expansion.
>
>> I'd have another, really, really close look at that pendulum. The
>> thermal compensation mechanism may not be that obvious.
> I have a 1903 bracket clock with pendulaum. It is NOT a temperature
> compensated one.
>

Does it run slower or faster in hot weather?

[newshound]

That's a *very* interesting point. Wood seems to have an expansion
coefficient of around 3 x 10^-6, the first reference I checked gave
brass as 10 to 19 * 10^-6 (both per degree C).

[NY]

"newshound" <news...@stevejqr.plus.com> wrote in message

news:h9adnTaqYIhSz_nG...@brightview.co.uk...

>> How is the pendulum bob fixed to the rod? I have a 1900-ish pendulum
>> clock whose flat circular bob is supported at its bottom. So as the
>> temperature rises the bob's center of gravity moves upwards and tends to
>> compensate for expansion of the rod downwards. The clock keeps excellent
>> time, within 5 seconds per day when compared with a radio-controlled
>> clock. This is despite its pendulum rod being made of wood which I would
>> expect to be affected by atmospheric humidity, but it doesn't seem to
>> be.

The pendulum on this clock supported at the bottom like that. Goodness knows
how the length is adjusted, because the weight doesn't move freely up and
down the rod, resting on a nut that you can wind up and down a threaded rod.
It looks as if you have to rotate the whole weight to move it up and down
the screw, but if that's how you adjust it, it's very stiff and I'm not
about to try it in case I break something. I just correct it each morning
(and maybe in between if I notice it's wrong) so it remains no more than a
couple of minutes fast.

+/- 5 seconds a day is pretty bloody amazing for a clockwork clock. It's
good even for a quartz clock: the real time clock on my PC loses or gains
more than that, but then gets corrected by scheduled process syncing with
time.windows.com (or whatever) every 24 hours; I think the worst I've seen
it (compared with time.is) is about 90 seconds out.

How long did it take to get it that accurate, given that you have to make a
small adjustment to the pendulum length and then wait ages to see how much
time it has lost over maybe 24 hours to work out how much further you need
to adjust the screw, iteratively homing in on the correct setting. I suppose
if you know the gearing of the clock (pendulum ticks per minute of hand
movement) you can time a few ticks and extrapolate from there - but the more
ticks you count, the less measurement error there will be.

Actually, it's uncanny. When I went to check the pendulum fixing just now, I
found that the clock had stopped literally a minute or so ago, after I'd
forgotten to wind it this morning. What is the chance of it stopping exactly
at the time that I check the clock?


This is a very old full-height grandfather clock that has been in the family
for years. It's named Francis after a distant ancestor who was a
clock-maker. It would have been incredible to have found one of his own
clocks in an antique shop, but my parents did the next best thing and bought
one from a clockmaker who had lived in the same part of the country at about
the same time - which I think was early 19th century. I presume the
mechanism is original - in design, even if some parts have been replaced
like-for-like over the years.

You'd tend to expect a big clock to have a deep sonorous chime, but this one
has a little bell about the pitch of a bell used on a shop counter for
attracting the assistant's attention - a bit weedy, as if its voice hasn't
broken. The chiming mechanism is a bit uneven: I presume it has a wind vane
that crudely regulates the interval between the chimes, and sometimes for no
apparent reason you get a few chimes with a bit of time between them and
then a couple of hurried ones at the end, as if it's saying "Sod it. Twelve
o'clock is a lot of hard work. I'm nearly there, try and get the rest over
quickly." But that just gives it character ;-)

[newshound]

On 03/08/2018 14:39, Jethro_uk wrote:

> On Fri, 03 Aug 2018 14:31:01 +0100, NY wrote:
>
>> +/- 5 seconds a day is pretty bloody amazing for a clockwork clock.
>

> Didn't Harrisons watch (which had to go to sea) far exceed that. In the
> 1700s ?
>
Harrison's H4 was pretty incredible, but in fact the French were close
behind

https://en.wikipedia.org/wiki/Marine_chronometer

Can't immediately spot the accuracy of the H4, but this link has an
unreferenced statement suggesting that mechanical marine chronometers
got to 0.1 seconds per day, giving an accuracy of 1 - 2 miles after a
sea voyage of a month.

[newshound]

Here's a better one

https://www.theguardian.com/science/2015/apr/19/clockmaker-john-harrison-vindicated-250-years-absurd-claims

0.6 seconds over 100 days, and that was a pendulum clock to Harrison's
design (though not, of course, at sea on a sailing ship).

[NY]

"Jethro_uk" <jeth...@hotmailbin.com> wrote in message
news:pk1lua$539$5...@dont-email.me...

> On Fri, 03 Aug 2018 14:31:01 +0100, NY wrote:
>

>> +/- 5 seconds a day is pretty bloody amazing for a clockwork clock.
>

> Didn't Harrisons watch (which had to go to sea) far exceed that. In the
> 1700s ?

Yes but it was probably a far more elaborate mechanism with far more checks
and counter checks that a normal clock mechanism. To make something that
keeps consistent time, in a range of temperatures and on board a heaving
ship, was a fantastic achievement. And it must have taken ages to adjust the
clock, little by little, until it was keeping the correct time, even if once
it *had* been set, it remained accurate. I presume it was a rotating balance
wheel as opposed to a pendulum, so it would be a matter of tweaking the
length of the spring. And what would they have used as a reference against
which to measure how far fast or slow the Harrison watch was, while
adjusting it. I suppose for a fixed location, the movement of the stars is
known so you can tell the time fairly accurately using those and compare the
watch against that.

Come to think of it, I wonder why my PC clock is so bad. Quartz watches keep
better time and don't need much adjustment back to correct time. I wonder if
when the PC is on, it uses some other time source than the quartz crystal.

[newshound]

PC clocks were never particularly accurate because they didn't need to
be. Doesn't everything get time from the internet these days?

[Bob Eager]

On Fri, 03 Aug 2018 15:04:24 +0100, newshound wrote:

> PC clocks were never particularly accurate because they didn't need to
> be.
> Doesn't everything get time from the internet these days?

We have one clockwork clock. All the rest get their time via NTP, or from
Anthorn.

--
My posts are my copyright and if @diy_forums or Home Owners' Hub
wish to copy them they can pay me £1 a message.
Use the BIG mirror service in the UK: http://www.mirrorservice.org
*lightning surge protection* - a w_tom conductor

[NY]

"Bob Eager" <news...@eager.cx> wrote in message
news:fsj5q0F...@mid.individual.net...

>> Doesn't everything get time from the internet these days?
>
> We have one clockwork clock. All the rest get their time via NTP, or from
> Anthorn.

A clock only needs to be as accurate as the gain or loss that you can
tolerate in the interval until it is next synchronised with a master time
source.

Windows defaults to syncing once a week. After I found my PCs drifting by
several minutes, I changed that to once every day. It's a shame that it
requires a registry change, and isn't changeable from a menu built into
Windows.

As I understand it, the Raspberry Pi doesn't have a battery-backed real time
clock, and has to set itself afresh every time it is booted and can talk to
an NTP server. I presume it resyncs periodically while it is running.


I'm cautious of clocks that have no free-running capability, which depend
entirely on a radio source. My wife bought a Rugby clock/radio years ago and
towards the end it started displaying bizarre times, probably if it lost the
radio signal, because it couldn't keep going (even if with a slight error)
until the next time it got a valid time. Not good when it's the alarm clock
that wakes you to go to work :-(

[Harry Bloomfield]

T i m submitted this idea :

> Lower viscosity of the lubrication on the lighter / faster moving bits
> = less drag?

Less drag, usually means the pendulum can swing higher, the higher it
swings, the slower it ticks.

[T i m]

On Fri, 3 Aug 2018 15:25:37 +0100, "NY" <m...@privacy.net> wrote:

<snip>

>As I understand it, the Raspberry Pi doesn't have a battery-backed real time
>clock, and has to set itself afresh every time it is booted and can talk to
>an NTP server. I presume it resyncs periodically while it is running.

Wouldn't all that be down to the OS running on it, so not the RPi
itself?

On one ESP32 project I built it makes a WiFi connection, connects to
an NTP server, logs the values of a temperature sensor to an SD card
and then goes to sleep for n time.

On my Arduino projects I have an external RTC.

Cheers, T i m

[Harry Bloomfield]

NY explained on 03/08/2018 :

> +/- 5 seconds a day is pretty bloody amazing for a clockwork clock.

I would expect much better than that, from a half decent mechanical
watch.

> It's good
> even for a quartz clock:

Again it depends upon the quality of the unit. The none adjustable
ones, yes +/- 5 seconds. I can usually adjust a decent one to +/- 1
second per week kept on the wrist.

> the real time clock on my PC loses or gains more
> than that, but then gets corrected by scheduled process syncing with
> time.windows.com (or whatever) every 24 hours; I think the worst I've seen it
> (compared with time.is) is about 90 seconds out.

Like some clocks, those are the very least accurate usually with no way
to trim them for best accuracy, besides there location subjects them to
wide temperature variations.

The most accurate crystal based clocks, have the crystal and oscillator
mounted in an oven or a double oven system. I have one which usually
manages 0.1 second per month.

I have a cheap Sekonda quartz, which manages around a surprising one
second per month on the wrist.

Most consistently accurate, for year in year out, are radio controlled
watches and clocks or ones synched via mobile mast/ internet.

[The Natural Philosopher]

Of course it doees. NTP on the internet> PROBABLY accurate to a ms or so.



--
"If you don’t read the news paper, you are un-informed. If you read the
news paper, you are mis-informed."

Mark Twain

[Harry Bloomfield]

NY used his keyboard to write :

> Come to think of it, I wonder why my PC clock is so bad. Quartz watches keep
> better time and don't need much adjustment back to correct time. I wonder if
> when the PC is on, it uses some other time source than the quartz crystal.

Microsoft syncs them to the Internet once per day.

[T i m]

But that's not a lighter / faster bit or the issue is it?

(The idea is) It's less drag on the things that regulate the thing
that regulates the time. ;-)

Do you have a more plausible reason?

Cheers, T i m

[NY]

"The Natural Philosopher" <t...@invalid.invalid> wrote in message
news:pk1sgk$48n$1...@dont-email.me...

>> I wonder if when the PC is on, it uses some other time source than the
>> quartz crystal.
> Of course it doees. NTP on the internet> PROBABLY accurate to a ms or so.

Ah, sorry, you misunderstood me. I was meaning for its free-running, in
between fairly rare resetting by an NTP source. I seem to remember some
bollocks about the RTC on a PC only using its quartz crystal to keep time
when the PC was off, and that it used another way of keeping time (using the
CPU) while the PC was booted to an operating system. But I can't remember
enough details to google it.

And then of course, while it is booted, it can synchronise to a master time
source to kick it back to correct time if the local tick (whether crystal or
something else) has drifted a bit.

Windows' default for NTP is as infrequent as once a week. I found the
registry tweak to change this to every 24 hours.

I've just checked with time.is and the clock is current 0.7 sec ahead,
having last synced at 22:15 last night (for once, the Date and Time |
Internet Time tab actually tells me when it last synced, usually that info
is not given for some reason).

[NY]

"Harry Bloomfield" <harry...@NOSPAM.tiscali.co.uk> wrote in message
news:pk1sk2$5rn$1...@dont-email.me...

I'm sure by default it's once a week. I remember changing it to once a day
when I found that my clock was sometimes as much as a couple of minutes
wrong when it was syncing once a week.

[The Natural Philosopher]

On 03/08/18 17:06, NY wrote:
> "The Natural Philosopher" <t...@invalid.invalid> wrote in message
> news:pk1sgk$48n$1...@dont-email.me...
>>> I wonder if when the PC is on, it uses some other time source than
>>> the quartz crystal.
>> Of course it doees. NTP on the internet> PROBABLY accurate to a ms or so.
>
> Ah, sorry, you misunderstood me. I was meaning for its free-running, in
> between fairly rare resetting by an NTP source. I seem to remember some
> bollocks about the RTC on a PC only using its quartz crystal to keep
> time when the PC was off, and that it used another way of keeping time
> (using the CPU) while the PC was booted to an operating system. But I
> can't remember enough details to google it.
>

That certainly was correct the last time I was involved - free running
oscillator taht is realtively ribbish at timekeeing.

> And then of course, while it is booted, it can synchronise to a master
> time source to kick it back to correct time if the local tick (whether
> crystal or something else) has drifted a bit.
>
> Windows' default for NTP is as infrequent as once a week. I found the
> registry tweak to change this to every 24 hours.
>
> I've just checked with time.is and the clock is current 0.7 sec ahead,
> having last synced at 22:15 last night (for once, the Date and Time |
> Internet Time tab actually tells me when it last synced, usually that
> info is not given for some reason).

IIRC linux is almost every minute...not sure

"Generally we can also call it as polling interval and minimum time is
64 sec and maximum time 1024 sec , but you can still change it as you
want by doing changes at /etc/ntp.conf."


--
If you tell a lie big enough and keep repeating it, people will
eventually come to believe it. The lie can be maintained only for such
time as the State can shield the people from the political, economic
and/or military consequences of the lie. It thus becomes vitally
important for the State to use all of its powers to repress dissent, for
the truth is the mortal enemy of the lie, and thus by extension, the
truth is the greatest enemy of the State.

Joseph Goebbels

[Harry Bloomfield]

T i m formulated on Friday :

> But that's not a lighter / faster bit or the issue is it?
>
> (The idea is) It's less drag on the things that regulate the thing
> that regulates the time. ;-)
>
> Do you have a more plausible reason?

No, just expressing my thoughts on the subject from knowing how
mechanical time-pieces generally behave. My best guess would be that
the pendulum does have some compensation built in and the compensation
is over compensating when the weather heats up.

[Harry Bloomfield]

NY wrote on 03/08/2018 :
> I'm sure by default it's once a week. I remember changing it to once a day
> when I found that my clock was sometimes as much as a couple of minutes wrong
> when it was syncing once a week.

I have just checked and W10's default is once per week, with no means
to change it - earlier versions did it once per day. I use a utility
which sets my PC once every hour NetTime, because I am fixing a few of
my old watches up at the moment and I need accurate references.

[Robin]

Ahem, I think you may temporarily have overlooked that a - if not the -
point about using a pendulum for timekeeping is that the period of
oscillation is independent of the amplitude.

--
Robin
reply-to address is (intended to be) valid

[Harry Bloomfield]

It happens that Jethro_uk formulated :
> Which, given the nature of TCP/IP is quite a feat.

The clock setting utils, check the average path delay to the time
servers, then adjust the time suit.

https://time.is/ give a constant accurate on screen time reference,
compared against your PC's clock.

[NY]

"Robin" <r...@outlook.com> wrote in message
news:c3ea8d1e-9eb3-bd80...@outlook.com...

> On 03/08/2018 16:14, Harry Bloomfield wrote:
>> T i m submitted this idea :
>>> Lower viscosity of the lubrication on the lighter / faster moving bits
>>> = less drag?
>>
>> Less drag, usually means the pendulum can swing higher, the higher it
>> swings, the slower it ticks.
>
> Ahem, I think you may temporarily have overlooked that a - if not the -
> point about using a pendulum for timekeeping is that the period of
> oscillation is independent of the amplitude.

There's also the fact that a pendulum only obeys an *approximation* to
simple harmonic motion, and this gets progressively worse as the angle of
swing increases. I'm not sure whether the period actually alters if the
swing is too wide.

But I agree, for normal amounts of swing, a fundamental defining
characteristic of a pendulum's usefulness ought to be that it is independent
of swing.

[Harry Bloomfield]

NY was thinking very hard :

> Ah, sorry, you misunderstood me. I was meaning for its free-running, in
> between fairly rare resetting by an NTP source. I seem to remember some
> bollocks about the RTC on a PC only using its quartz crystal to keep time
> when the PC was off, and that it used another way of keeping time (using the
> CPU) while the PC was booted to an operating system. But I can't remember
> enough details to google it.

The PC reads the RTC as it boots, then the PC maintains it own separate
version of time until next boot. What you see when you check the time
on your PC is the PC's version. Adjusting the time, writes to both
clocks.

[Robin]

On 03/08/2018 17:24, Robin wrote:
> On 03/08/2018 16:14, Harry Bloomfield wrote:
>> T i m submitted this idea :
>>> Lower viscosity of the lubrication on the lighter / faster moving bits
>>> = less drag?
>>
>> Less drag, usually means the pendulum can swing higher, the higher it
>> swings, the slower it ticks.
>
> Ahem, I think you may temporarily have overlooked that a - if not the -
> point about using a pendulum for timekeeping is that the period of
> oscillation is independent of the amplitude.
>

<sigh>

Sod's law of course then means that I had to forget to add "for small
amplitudes that is"


sorry

<sigh>

to make up for it, I've dug out one of the formulae for the true period.
That suggests the pendulum would need to increase its amplitude by
about 15 per cent to make a difference of 10 seconds a day

[Robin]

On 03/08/2018 17:34, NY wrote:
> "Robin" <r...@outlook.com> wrote in message
> news:c3ea8d1e-9eb3-bd80...@outlook.com...
>> On 03/08/2018 16:14, Harry Bloomfield wrote:
>>> T i m submitted this idea :
>>>> Lower viscosity of the lubrication on the lighter / faster moving bits
>>>> = less drag?
>>>
>>> Less drag, usually means the pendulum can swing higher, the higher it
>>> swings, the slower it ticks.
>>
>> Ahem, I think you may temporarily have overlooked that a - if not the
>> - point about using a pendulum for timekeeping is that the period of
>> oscillation is independent of the amplitude.
>
> There's also the fact that a pendulum only obeys an *approximation* to
> simple harmonic motion, and this gets progressively worse as the angle
> of swing increases. I'm not sure whether the period actually alters if
> the swing is too wide.
>

thanks - though it'd have been even more helpful if you'd nudged me on
that before I posted ;)

[Harry Bloomfield]

The Natural Philosopher formulated on Friday :

> That certainly was correct the last time I was involved - free running
> oscillator taht is realtively ribbish at timekeeing.

My recollection is that it used(s) the CPU's own crystall oscillator,
rather than a free running oscillator. Still rubbish at keeping time
though.

In the pre NTP days, I used to have a TSR, which would frequently
adjust both clocks, based on time running and time off.

[The Natural Philosopher]

On 03/08/18 17:24, Robin wrote:
> On 03/08/2018 16:14, Harry Bloomfield wrote:
>> T i m submitted this idea :
>>> Lower viscosity of the lubrication on the lighter / faster moving bits
>>> = less drag?
>>
>> Less drag, usually means the pendulum can swing higher, the higher it
>> swings, the slower it ticks.
>
> Ahem, I think you may temporarily have overlooked that a - if not the -
> point about using a pendulum for timekeeping is that the period of
> oscillation is independent of the amplitude.
>

It is not.

It is approximately true for small angles of swing


--
All political activity makes complete sense once the proposition that
all government is basically a self-legalising protection racket, is
fully understood.

[The Natural Philosopher]

On 03/08/18 17:34, NY wrote:
> "Robin" <r...@outlook.com> wrote in message
> news:c3ea8d1e-9eb3-bd80...@outlook.com...
>> On 03/08/2018 16:14, Harry Bloomfield wrote:
>>> T i m submitted this idea :
>>>> Lower viscosity of the lubrication on the lighter / faster moving bits
>>>> = less drag?
>>>
>>> Less drag, usually means the pendulum can swing higher, the higher it
>>> swings, the slower it ticks.
>>
>> Ahem, I think you may temporarily have overlooked that a - if not the
>> - point about using a pendulum for timekeeping is that the period of
>> oscillation is independent of the amplitude.
>
> There's also the fact that a pendulum only obeys an *approximation* to
> simple harmonic motion, and this gets progressively worse as the angle
> of swing increases. I'm not sure whether the period actually alters if
> the swing is too wide.
>

yes. It does. Imagine if it ALMOST goes full circle and hesitates at the
top...and falls back down.

> But I agree, for normal amounts of swing, a fundamental defining
> characteristic of a pendulum's usefulness ought to be that it is
> independent of swing.

In reality it is given just enough impetus to have a CONNSTANT amplitude
of swing.

[T i m]

On Fri, 03 Aug 2018 17:17:09 +0100, Harry Bloomfield
<harry...@NOSPAM.tiscali.co.uk> wrote:

>T i m formulated on Friday :
>> But that's not a lighter / faster bit or the issue is it?
>>
>> (The idea is) It's less drag on the things that regulate the thing
>> that regulates the time. ;-)
>>
>> Do you have a more plausible reason?
>
>No,

Ok?

>just expressing my thoughts on the subject from knowing how
>mechanical time-pieces generally behave.

Ok.

>My best guess would be that
>the pendulum does have some compensation built in and the compensation
>is over compensating when the weather heats up.

Ok, so that could be an equally plausible reason. ;-)

Cheers, T i m

[harry]

Fine weather = high air pressure = denser = more resistance.
Maybe it's to do with humidity.

[NY]

"Harry Bloomfield" <harry...@NOSPAM.tiscali.co.uk> wrote in message

news:pk1vg0$ph0$1...@dont-email.me...

On older versions of Windows (certainly up to and including W7) there's a
key which sets the number of seconds between polls of the NTP server). I
wonder if W10 doesn't use it. The key is

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\W32Time\TimeProviders\NtpClient\SpecialPollInterval

That's SPECIALPOLLINTERVAL (a lower-case L and and upper-case i look
identical in some fonts).

On a default installation of Windows, the value is 604800 (7 days) but I've
set it to 86400 (1 day).

You need to restart the W32TIME service for it to pick up changes in the
key.

My only Win10 PC is difficult to get at right now, otherwise I'd try
changing the key and seeing whether W10 honours it - eg set it to 1 minute,
restart W32TIME, manually set the time to an almost-correct value and then
check that it magically changes to the correct time within a minute.

[Harry Bloomfield]

NY explained :

I know about the key and I found it in W10, setting it seemed to make
no difference at all that I could tell. I have used the same key before
in previous versions and had it work fine.

[Harry Bloomfield]

harry wrote on 03/08/2018 :
> Fine weather = high air pressure = denser = more resistance.
> Maybe it's to do with humidity.

Air is denser in cold weather.

[Archibald Tarquin Blenkinsopp]

On Fri, 3 Aug 2018 18:00:39 +0100, The Natural Philosopher
<t...@invalid.invalid> wrote:

>On 03/08/18 17:34, NY wrote:
>> "Robin" <r...@outlook.com> wrote in message
>> news:c3ea8d1e-9eb3-bd80...@outlook.com...
>>> On 03/08/2018 16:14, Harry Bloomfield wrote:
>>>> T i m submitted this idea :
>>>>> Lower viscosity of the lubrication on the lighter / faster moving bits
>>>>> = less drag?
>>>>
>>>> Less drag, usually means the pendulum can swing higher, the higher it
>>>> swings, the slower it ticks.
>>>
>>> Ahem, I think you may temporarily have overlooked that a - if not the
>>> - point about using a pendulum for timekeeping is that the period of
>>> oscillation is independent of the amplitude.
>>
>> There's also the fact that a pendulum only obeys an *approximation* to
>> simple harmonic motion, and this gets progressively worse as the angle
>> of swing increases. I'm not sure whether the period actually alters if
>> the swing is too wide.
>>
>yes. It does. Imagine if it ALMOST goes full circle and hesitates at the
>top...and falls back down.

A common problem with pendulum clocks. I believe the problem was
solved by virtue of the Notwen Elppa damping system. One of these
little units will ensure that no pendulum goes into overdrive.

Operating without same can tip the balance and induce positive
feedback into the pendelum thus having a destabilising effect on the
space time continuum.

AB

[newshound]

On 03/08/2018 17:34, NY wrote:

Also, the amplitude of the pendulum will (almost) be controlled by the
escapement. There will be a second order effect though.

[newshound]

But I don't think it is the density which controls the resistance, but
the viscosity, which goes in the other direction.

[Rod Speed]

"Harry Bloomfield" <harry...@NOSPAM.tiscali.co.uk> wrote in message

news:pk1sk2$5rn$1...@dont-email.me...

That varys with the OS.

[Johnny B Good]

Checked my desktop's clock just now against Time.is

"Your time is exact!
The difference from Time.is was -0.003 seconds (±0.044 seconds)."

IIRC, I got a similar result the last time I tried this some months or
years ago.

I've been running Linux Mint 17.1 KDE64 for just over 3 years now so
have no idea of just how shite the MoBo's RTC actually is[1]. The quartz
crystal oscillators are stable enough, the problem is the manufacturers
simply can't be arsed to calibrate them[2].

The later versions of MS windows are pretty shoddy with regard to
syncing to NTP. That business of leaving the System Time to go unchecked/
corrected for a week at a time is yet one more minor (in the overall
scheme of MS badness) thing not to like about windows ten.

Just refreshed the page...

"Your time is exact!
The difference from Time.is was +0.001 seconds (±0.043 seconds)."

and a minute later...

"Your time is exact!
The difference from Time.is was +0.000 seconds (±0.044 seconds)."

That's via Opera's VPN. I'll turn off the VPN and try again.

"Your time is exact!
The difference from Time.is was +0.012 seconds (±0.026 seconds).

That's about what I'd expect having eliminated the extra latency of
Opera's VPN service. It also confirms that my 13 year old Casio Data Bank
360 watch is still one second ahead since the last time I had to rescue
it from January the first 2000[3] a week or so back.

Ever since I disabled the VPN option, subsequent refreshes with time.is
have been giving differences in the +0.012 and +0.011 range (±0.025
seconds). The last time I checked the time.is site under win2k, ISTR
seeing variations of 2 or 3 seconds between ntp sync events (but that was
with the previous MoBo which may or may not have had a less inaccurate
RTC).

=========================================================================

[NOTES]

[1] The OS upgrade from win2k to Linux Mint being the result of a major
hardware upgrade that had sidelined win2k (lack of driver support and
more importantly, the waste of a 64 bit CPU on a 32 bit OS).

The consequence being that I've been shielded from the RTC's
shortcomings as a cheap watch by Linux Mint's NTP daemon service which
not only takes care of syncing with ntp services, it also applies a
correction factor to the system clock to keep drift to a minimum, unlike
MS windows' system clock's time keeping.

With win2k at least, the user could choose their own internet time
synchronising schedule. AFAICR, I set mine on a 3 hour 59 minute schedule
to reduce clashes with requests from "The Whole World and their Dog" as a
compromise between overloading the servers and the clock error getting
out of hand.

I'd have to shut the PC down and unplug from the LAN, leave it say 12
hours and make sure to go straight into the cmos setup when I next power
up to see the RTC time before Linux gets its chance to 'correct the time'
using its calibrated correction factor when it's unable to access the
internet, if I want to see just how piss poor the RTC's accuracy is for
the lack of any attempt at calibration by the MoBo manufacturer.

[2] Not even to the humble timekeeping standards of your typical quartz
watch (a lousy +/- 30 seconds a month when, with a bit of care, they can
readily be set to stay within +/-1 second a month from one year's end to
the next before needing another tweak - assuming access to the padding
trimmer, not a normal option in the typical on-board RTC oscillator).

[3] It has the best thought out digital watch display I've *ever* seen
but after 9 years of faithful service, just as it had finally settled
down to an accuracy of +/- 1 second per annum, it took to blanking out/
resetting itself to the 1st of January 2000 every few months or so.

The last time I had to rescue it from its brief sojourn in the past, the
'shock' of the 'rescue' was so severe, the pin holding the retaining
toggle on the adjustable clasp of the stainless steel bracelet jumped
free. Luckily, I was able to find it and reassemble the clasp.

I really aught to replace it but the only digital watch that comes close
to the display ergonomics of my quirky Casio is another DB360 and the
only sensibly priced sources seem to be Ebay traders so I've played my
strong suite and procrastinated like crazy - it's what I do best.

--
Johnny B Good

[Max Demian]

On 03/08/2018 18:00, The Natural Philosopher wrote:
> On 03/08/18 17:34, NY wrote:
>> "Robin" <r...@outlook.com> wrote in message
>> news:c3ea8d1e-9eb3-bd80...@outlook.com...
>>> On 03/08/2018 16:14, Harry Bloomfield wrote:
>>>> T i m submitted this idea :
>>>>> Lower viscosity of the lubrication on the lighter / faster moving bits
>>>>> = less drag?
>>>>
>>>> Less drag, usually means the pendulum can swing higher, the higher
>>>> it swings, the slower it ticks.
>>>
>>> Ahem, I think you may temporarily have overlooked that a - if not the
>>> - point about using a pendulum for timekeeping is that the period of
>>> oscillation is independent of the amplitude.
>>
>> There's also the fact that a pendulum only obeys an *approximation* to
>> simple harmonic motion, and this gets progressively worse as the angle
>> of swing increases. I'm not sure whether the period actually alters if
>> the swing is too wide.
>>
> yes. It does. Imagine if it ALMOST goes full circle and hesitates at the
> top...and falls back down.
>
>> But I agree, for normal amounts of swing, a fundamental defining
>> characteristic of a pendulum's usefulness ought to be that it is
>> independent of swing.

> In reality it is given just enough impetus to have a CONNSTANT amplitude
> of swing.

The theory states that the period of oscillation is independent of the
amplitude if the centre of gravity of the pendulum describes a *cycloid*
which is the locus of a point on the circumference of a circle, rather
than an arc of a circle. (A cycloid looks like a circular arc which is
turned up at the ends.) This was worked out by Christiaan Huygens,
inventor of the pendulum clock.

Some pendulum clocks achieve this by means of cycloidal jaws
constraining the suspension spring.

More usually the amplitude is kept small, where a circular arc
approximates to a cycloid, or the amplitude is kept as nearly constant
as possible.

--
Max Demian

[Martin Brown]

On 03/08/2018 15:25, NY wrote:
> "Bob Eager" <news...@eager.cx> wrote in message
> news:fsj5q0F...@mid.individual.net...

>>> Doesn't everything get time from the internet these days?
>>
>> We have one clockwork clock. All the rest get their time via NTP, or from
>> Anthorn.

Some get their time from GPS if they want greater precision.

> A clock only needs to be as accurate as the gain or loss that you can
> tolerate in the interval until it is next synchronised with a master
> time source.

It only *needs* to be that accurate but there is real clockmakers kudos
in having something that drifts by only a miniscule amount over the
period where it needs to be rewound. 200 day clocks for instance.

Marine chronometers and observatory clocks at the beginning of the last
century represented the peak performance of classic mechanical clocks.
They also included cunning mechanisms that prevent rewinding interfering
with the accuracy and amplitude of the pendulum beat.

The Shortt-Synchronome was the ultimate in precision mechanical clocks -
good enough to detect seasonal variations in the Earth's rotation back
in the 1920's - long before atomic clocks.

http://clockvault.com/heritage/

> Windows defaults to syncing once a week. After I found my PCs drifting
> by several minutes, I changed that to once every day. It's a shame that
> it requires a registry change, and isn't changeable from a menu built
> into Windows.

That is mainly because the designers CBA to load and trim the crystal
properly unlike the ones in cheap watches which are usually done right.

> As I understand it, the Raspberry Pi doesn't have a battery-backed real
> time clock, and has to set itself afresh every time it is booted and can
> talk to an NTP server. I presume it resyncs periodically while it is
> running.

The original PC design didn't have an RTC either - you had to manually
set time and date every time you booted it (pre internet).

> I'm cautious of clocks that have no free-running capability, which
> depend entirely on a radio source. My wife bought a Rugby clock/radio
> years ago and towards the end it started displaying bizarre times,
> probably if it lost the radio signal, because it couldn't keep going
> (even if with a slight error) until the next time it got a valid time.
> Not good when it's the alarm clock that wakes you to go to work :-(

Domestic "atomic clocks" usually do have a local RTC that is disciplined
by the incoming signal to trim it when free running to fractions of a
ppm. Simpler ones just free run at whatever the crystal inside happens
to oscillate at.

My guess at the design of the pendulum that is running fast would be an
invar main pendulum bar with an iron weight that is about 1/10 its
length supported from below. This is approximately tempco = 0ppm.
Trouble is invar used to vary from batch to batch.

--
Regards,
Martin Brown

[AnthonyL]

My Windows XP's clock updated this morning and is next scheduled to
update the same time (+-) next week. I run SymmTime which is set to
update every 60mins from ntp0.pipex.net in Cambridge.
Disappointingly:

Time.is
Your time is exact!

The difference from Time.is was +0.011 seconds (ą0.056 seconds)

That would make the difference between finishing on pole and being on
the second row.

--
AnthonyL

[m...@hotmail.com]

On Fri, 3 Aug 2018 09:30:30 +0100, "NY" <m...@privacy.net> wrote:

>We have a very old pendulum grandfather clock - the pendulum is probably
>about 2 feet long with a slow tick. I've noticed that in the hot weather,
>when it's probably been warmer inside the house than normal, the clock is
>running *fast*. I would expect it to run slow, since the pendulum will
>lengthen slightly in the warmer temperature and
>
>t = 2 pi sqrt (l/g)
>
>as l increases, so does the time period t between ticks

We've had a lot of high pressure systems, there is a barrometric
effect on the pendulum too.

---
This email has been checked for viruses by AVG.
https://www.avg.com

[harry]

Who cares?
Nobody actually needs a clock to be that accurate.
Plus or minus five minutes is good enough for my needs

[Rod Speed]

"harry" <harry...@btinternet.com> wrote in message
news:2599d0e8-779d-476d...@googlegroups.com...

Wrong, as always.

> Plus or minus five minutes is good enough for my needs

But isnt when you use the PC as a PVR.

[Richard]

Your PC might need updating if still using a pendulum clock.

[Rod Speed]

"Richard" <smit...@btinternet.com.invalid> wrote in message
news:pk6d2m$1t8j$1...@gioia.aioe.org...

It doesn’t. That comment was about time, not pendulum clocks, stupid.

[T i m]

On Sat, 4 Aug 2018 23:46:07 -0700 (PDT), harry
<harry...@btinternet.com> wrote:

>On Friday, 3 August 2018 21:21:29 UTC+1, newshound wrote:
>> On 03/08/2018 18:55, harry wrote:
>> > On Friday, 3 August 2018 16:14:20 UTC+1, Harry Bloomfield wrote:
>> >> T i m submitted this idea :
>> >>> Lower viscosity of the lubrication on the lighter / faster moving bits
>> >>> = less drag?
>> >>
>> >> Less drag, usually means the pendulum can swing higher, the higher it
>> >> swings, the slower it ticks.
>> >
>> > Fine weather = high air pressure = denser = more resistance.
>> > Maybe it's to do with humidity.
>> >
>> But I don't think it is the density which controls the resistance, but
>> the viscosity, which goes in the other direction.
>
>Who cares?

Those interested in such things, especially horologists?

>Nobody actually needs a clock to be that accurate.

Do they?

>Plus or minus five minutes is good enough for my needs

Ah, then that makes you 'a nobody' (funny how the Fanatical Brexiteers
can only see everything from *their* POV).

5 minutes is a very long time if you miss a train, flight, the
beginning of the film, interview, auction or the launch.

Sorry, just remembered ... you are a Fanatic Brexiteer so don't like
standards ... probably want us to launch a new post Brexit 'Little
England only meantime'? 1440 +- 5 minutes / day?

Cheers, T i m

[newshound]

On 05/08/2018 07:46, harry wrote:
> On Friday, 3 August 2018 21:21:29 UTC+1, newshound wrote:
>> On 03/08/2018 18:55, harry wrote:
>>> On Friday, 3 August 2018 16:14:20 UTC+1, Harry Bloomfield wrote:
>>>> T i m submitted this idea :
>>>>> Lower viscosity of the lubrication on the lighter / faster moving bits
>>>>> = less drag?
>>>>
>>>> Less drag, usually means the pendulum can swing higher, the higher it
>>>> swings, the slower it ticks.
>>>
>>> Fine weather = high air pressure = denser = more resistance.
>>> Maybe it's to do with humidity.
>>>
>> But I don't think it is the density which controls the resistance, but
>> the viscosity, which goes in the other direction.
>
> Who cares?

Anyone who is interested in science?

[newshound]

On 04/08/2018 09:15, Martin Brown wrote:

>
> Marine chronometers and observatory clocks at the beginning of the last
> century represented the peak performance of classic mechanical clocks.
> They also included cunning mechanisms that prevent rewinding interfering
> with the accuracy and amplitude of the pendulum beat.
>
> The Shortt-Synchronome was the ultimate in precision mechanical clocks -
> good enough to detect seasonal variations in the Earth's rotation back
> in the 1920's - long before atomic clocks.
>
> http://clockvault.com/heritage/
>

Fascinating. This states that variations in atmospheric pressure are
enough to affect high accuracy pendulum clocks.

[dennis@home]

Not exactly high accuracy if the pressure affects it.
Maybe a suitable bellows mechanism is need in the pendulum?

[bert]

In article <pk1se2$4mj$1...@dont-email.me>, Harry Bloomfield
<harry...@NOSPAM.tiscali.co.uk> writes
>NY explained on 03/08/2018 :
>> +/- 5 seconds a day is pretty bloody amazing for a clockwork clock.
>
>I would expect much better than that, from a half decent mechanical
>watch.
>
>> It's good even for a quartz clock:
>
>Again it depends upon the quality of the unit. The none adjustable
>ones, yes +/- 5 seconds. I can usually adjust a decent one to +/- 1
>second per week kept on the wrist.
>
>> the real time clock on my PC loses or gains more than that, but then
>>gets corrected by scheduled process syncing with time.windows.com (or
>>whatever) every 24 hours; I think the worst I've seen it (compared
>>with time.is) is about 90 seconds out.
>
>Like some clocks, those are the very least accurate usually with no way
>to trim them for best accuracy, besides there location subjects them to
>wide temperature variations.
>
>The most accurate crystal based clocks, have the crystal and oscillator
>mounted in an oven or a double oven system. I have one which usually
>manages 0.1 second per month.
>
>I have a cheap Sekonda quartz, which manages around a surprising one
>second per month on the wrist.
>
That's better than my bloody Rolex!!
>Most consistently accurate, for year in year out, are radio controlled
>watches and clocks or ones synched via mobile mast/ internet.
Vehicle clocks seem to be particularly bad IME.
--
bert

[Bob Eager]

On Sun, 05 Aug 2018 17:48:22 +0100, bert wrote:

>>The most accurate crystal based clocks, have the crystal and oscillator
>>mounted in an oven or a double oven system. I have one which usually
>>manages 0.1 second per month.
>>
>>I have a cheap Sekonda quartz, which manages around a surprising one
>>second per month on the wrist.
>>
> That's better than my bloody Rolex!!
>>Most consistently accurate, for year in year out, are radio controlled
>>watches and clocks or ones synched via mobile mast/ internet.

Or...

https://en.wikipedia.org/wiki/Hoptroff_London


--
My posts are my copyright and if @diy_forums or Home Owners' Hub
wish to copy them they can pay me £1 a message.
Use the BIG mirror service in the UK: http://www.mirrorservice.org
*lightning surge protection* - a w_tom conductor

[newshound]

I'm still interested in the physical mechanism. The thread is about why
someone's clock runs fast (rather than slow) in hot weather, and there
have been suggestions that it might be the fact that atmospheric
pressure is consistently high (rather than that the temperature is hot)
which is the explanation. But high atmospheric pressure would cause more
drag on the pendulum, and thus should slow the clock down.

To my mind one of the more plausible explanations is that the C of G of
the metal "bob" might go up, shortening the period. But reduced drag in
lubricants is another possibility.

[newshound]

On 05/08/2018 18:58, Bob Eager wrote:
> On Sun, 05 Aug 2018 17:48:22 +0100, bert wrote:
>
>>> The most accurate crystal based clocks, have the crystal and oscillator
>>> mounted in an oven or a double oven system. I have one which usually
>>> manages 0.1 second per month.
>>>
>>> I have a cheap Sekonda quartz, which manages around a surprising one
>>> second per month on the wrist.
>>>
>> That's better than my bloody Rolex!!
>>> Most consistently accurate, for year in year out, are radio controlled
>>> watches and clocks or ones synched via mobile mast/ internet.
>
> Or...
>
> https://en.wikipedia.org/wiki/Hoptroff_London
>
>

Wikipedia editing fail!

"However, the technology used its quartz timepieces is still unknown to
the public."

[NY]

"bert" <be...@bert.bert.com> wrote in message
news:rhJxYjOW...@ghcq.uk...

> In article <pk1se2$4mj$1...@dont-email.me>, Harry Bloomfield
> <harry...@NOSPAM.tiscali.co.uk> writes
>>NY explained on 03/08/2018 :
>>> +/- 5 seconds a day is pretty bloody amazing for a clockwork clock.
>>
>>I would expect much better than that, from a half decent mechanical watch.

I've never had a clockwork clock that has been anywhere *near* as accurate
as a few seconds a day. Most seem to gain or lose up to five minutes a day:
you get used to that fact that this one gains and this one loses. And trying
to adjust the length of the pendulum or the tension in the balance wheel
spring is a never-ending chore of tweaking it one way, finding that I've
converted a small gain into a large loss, making a smaller tweak in the
opposite direction (hoping to do a binary chop to home in on the correct
setting), only to find that it defies all logic and loses even more. I think
the position of the pendulum screw on my smaller grandmother clock is
totally unrelated to the amount it gains or loses. Sadly that clock is
waiting for me to find a repairer, after it stopped working when we moved
house, even though I removed the pendulum and laid the clock horizontally in
the boot, surrounded by other things so it couldn't slide. It now runs for a
few minutes, with a tick that starts as a fairly even tick-tock, but then it
starts "limping" - the interval between the tick and the tock becomes longer
than that between the tock and the tick, until eventually the ticking gets
fainter and fainter, and them dies altogether.

Hope fully when I get that clock repaired, the mystery of the adjustment
screw and its relationship to the amount the clock gains or loses can be
solved.

[newshound]

As a teenager in the 1960's I decided to invest in a stopwatch
wristwatch to take to university (reading physics, so stopwatch used in
quite a lot of practicals in those days). Not silly money, around £20
IIRC. After a fair bit of tweaking I managed to get it good to a few
seconds a day, and it stayed that accurate for several years, although
it got a bit more random after that, presumably because of wear. The
good old says when you could rely on the time signal on the radio!

[dennis@home]

Well I don't believe anyone has mentioned the special thermally
compensated pendulums that consist of several lengths of different wire
running up and down the pendulum so its centre of mass stays in same
place when the temperature rises so its probably the length of the
pendulum changing.

If it has been copied for cosmetic reasons rather than using the correct
alloys anything could happen.

[Thomas Prufer]

On Sun, 5 Aug 2018 20:59:58 +0100, newshound <news...@stevejqr.plus.com>
wrote:

>To my mind one of the more plausible explanations is that the C of G of
>the metal "bob" might go up, shortening the period. But reduced drag in
>lubricants is another possibility.

But, but...

CoG would be a first-order effect, and drag and viscosity of air or lubricant an
second order-effect?


Thomas Prufer

[The Natural Philosopher]

Well maybe

"The difference between this true period and the period for small swings
(1) above is called the circular error. In the case of a typical
grandfather clock whose pendulum has a swing of 6° and thus an amplitude
of 3° (0.05 radians), the difference between the true period and the
small angle approximation (1) amounts to about 15 seconds per day. "

Thank you wiki. So amplitude of swing is definitley in te second order,m
raytetr than the 3,4, 5th order effects

15 seconds per day is around one in 5000 or 200 parts per million.

Now what does the change in pendulum length give us..

let's go from say 20 degrees C to 30 degrees C on a steel pendulum shaft.

https://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html

That is around 110-125 parts per million

Oh dear. Its in the same ballpark as amplitude.

Note that lead is around 300ppm over the same temperature range, which
suggests that a long lead bob of around 30% of the length of the steel
pendulum BOTTOM mounted should give a decent sort of temeperature
compensation.

Where does this leave us? well in the same shit we were in already. At
least two possible effects - thermal expnasion and frictional reduction
leading to larger amplitudes are in theiry capable of altring te clock
times. In unpredictable directions - since most pendulum clocks are
thermally compensated, it maye be that they are OVER compensated to
allow better accuracy over more normal temperature swings.


--
If I had all the money I've spent on drink...
..I'd spend it on drink.

Sir Henry (at Rawlinson's End)

[NY]

"The Natural Philosopher" <t...@invalid.invalid> wrote in message
news:pk99gu$bor$1...@dont-email.me...

In the case of my clock, the pendulum is about 1.2 m long, made of
rust-coloured rod about 2 mm diameter which is almost straight but very
slightly wiggly in places. The pendulum bob is a brass disc about 10 cm
diameter, supported at the bottom so thermal expansion *may* move its C of G
closer to the pivot point, compensating for expansion in the length of the
rod. I say "may" because the bob seems to be attached firmly to the rod,
rather than resting on it, so the centre of the bob may not be able to rise
as it expands - it may be better to regard the bob as being attached at its
centre rather than its bottom.

https://s22.postimg.cc/j57t1q7oh/20180806_121906.jpg
https://s22.postimg.cc/bch59rh4x/20180806_121927.jpg
https://s22.postimg.cc/5oauiuhxd/DSC_0140.jpg

These show the mechanism (side-on) with the rod attached to a torsion strip
of flexible metal and the attachment to the escapement, and the pendulum
bob. It took several attempts to get the pendulum bob in the right place,
not obscured by the winding chain, because my camera seemed to have a long
delay between pressing the shutter button and the shutter/flash firing. Not
sure what's going on there because the SLR (which I used for the photo of
the bob) should fire instantaneously.

The period of the pendulum is 2.0 seconds (averaged over about 10 cycles),
made up of 1.16 sec to the opposite side and 0.84 sec to return to the
start - so the tick and the tock are not quite evenly spaced.

[newshound]

The OP specifically said it was *not* a compensated pendulum. Apparently
it is a wooden rod with a metal (brass, lead?) fixed at the bottom (so
that the CofG may move upwards with increasing temperature)

[NY]

"newshound" <news...@stevejqr.plus.com> wrote in message
news:vvqdnchPSMESpPXG...@brightview.co.uk...

> The OP specifically said it was *not* a compensated pendulum. Apparently
> it is a wooden rod with a metal (brass, lead?) fixed at the bottom (so
> that the CofG may move upwards with increasing temperature)

Metal, not wooden, rod. Looks like iron or brass, but dark, not silvery
(iron) or yellow (brass), so very tarnished with age.

[newshound]

On 06/08/2018 12:49, NY wrote:
> "The Natural Philosopher" <t...@invalid.invalid> wrote in message

>
>

> In the case of my clock, the pendulum is about 1.2 m long, made of
> rust-coloured rod about 2 mm diameter which is almost straight but very
> slightly wiggly in places. The pendulum bob is a brass disc about 10 cm
> diameter, supported at the bottom so thermal expansion *may* move its C
> of G closer to the pivot point, compensating for expansion in the length
> of the rod. I say "may" because the bob seems to be attached firmly to
> the rod, rather than resting on it, so the centre of the bob may not be
> able to rise as it expands - it may be better to regard the bob as being
> attached at its centre rather than its bottom.
>
> https://s22.postimg.cc/j57t1q7oh/20180806_121906.jpg
> https://s22.postimg.cc/bch59rh4x/20180806_121927.jpg
> https://s22.postimg.cc/5oauiuhxd/DSC_0140.jpg
>
> These show the mechanism (side-on) with the rod attached to a torsion
> strip of flexible metal and the attachment to the escapement, and the
> pendulum bob. It took several attempts to get the pendulum bob in the
> right place, not obscured by the winding chain, because my camera seemed
> to have a long delay between pressing the shutter button and the
> shutter/flash firing. Not sure what's going on there because the SLR
> (which I used for the photo of the bob) should fire instantaneously.
>
> The period of the pendulum is 2.0 seconds (averaged over about 10
> cycles), made up of 1.16 sec to the opposite side and 0.84 sec to return
> to the start - so the tick and the tock are not quite evenly spaced.

That's an interesting point. ISTR that you normally try to adjust the
mechanism so that the swing is symmetrical either by tilting the case,
or adjusting the whole mechanism within it. Perhaps some simple thermal
expansion effect shows up if there is assymetry.

[Terry Casey]

In article
<j_SdneWpwvT69PrG...@brightview.co.uk>,
m...@privacy.net says...

>
> It now runs for a
> few minutes, with a tick that starts as a fairly even tick-tock, but then it
> starts "limping" - the interval between the tick and the tock becomes longer
> than that between the tock and the tick, until eventually the ticking gets
> fainter and fainter, and them dies altogether.
>

That means that the pendulum is no long swinging equally about
the vertical.

It used to be common when I was a kid to find mantlepiece
clocks propped up at one end or the other with a piece of
folded paper or card to get them to run smoothly. With wall
mounted clocks, it usually means it's mounted slightly skew-
whiff.

The actual answer is quite simple: the pendulum has a friction
clutch at the top to adjust its position with trespect to the
movement.

If the clock is wall hung, use a spirit level to get it
perfectly vertical and make a small mark on the wall so that
you can see immediately if it has moved.

Now start the clock and see if that cures the problem. If not,
you need to adjust the pendulum's vertical position

Move the pendulum to one end of its natural travel range and
keeping going slightly further, just overcoming the
resistance.

Start the clock and listen. Is it better or worse? If better
keep nudging the pendulum a bit further in the same direction
and try again. If it is now worse, move the pendulum in the
opposite direction, again moving it past its natural end stop.

Repeat the adjustments until the clock sounds right. All
things being equal, it should now carry on ticking without
stopping.





--

Terry

[whisky-dave]

On Friday, 3 August 2018 09:30:35 UTC+1, NY wrote:
> We have a very old pendulum grandfather clock - the pendulum is probably
> about 2 feet long with a slow tick. I've noticed that in the hot weather,
> when it's probably been warmer inside the house than normal, the clock is
> running *fast*. I would expect it to run slow, since the pendulum will
> lengthen slightly in the warmer temperature and
>
> t = 2 pi sqrt (l/g)
>
> as l increases, so does the time period t between ticks
>

> The pendulum is a single rod, not a multi-bar rod with two different metals
> so as to compensate for thermal expansion.

Might be some clue here.

https://www.ehow.com/about_5390207_do-slow-down-warmer-weather.html
or you live in an alternatoive universe

[whisky-dave]

I doubt many use an old grandfather clock to set a PVR or a PC.

[newshound]

Sorry, my mistake; but another poster *does* have a wooden one (and this
does have a surprisingly low expansion coefficient)

[newshound]

That's a pretty light-weight link. If the OP claims to observe the
opposite effect, I am inclined to believe them.

[whisky-dave]

On Monday, 6 August 2018 17:07:27 UTC+1, newshound wrote:

>
> Sorry, my mistake; but another poster *does* have a wooden one (and this
> does have a surprisingly low expansion coefficient)

His name wasn't Pinokio was it ;-)

[Jim Ericsson]

On 06/08/2018 12:49, NY wrote:

> https://s22.postimg.cc/5oauiuhxd/DSC_0140.jpg
>

I was going to flippantly say the pendulum was made of Zirconium
tungstate a material with a negative thermal coefficient, but this
picture gives me another idea.

The picture clearly shows that the pendulum has rubbed against the
wooden case, this would slow it down. Perhaps the clock was adjusted to
take this rubbing into account when cool but at higher temperatures the
rubbing stops or is lessened by movement of the pendulum due to thermal
expansion?

[NY]

"Jim Ericsson" <m...@privacy.net> wrote in message
news:KndaD.2032644$Vs7.1...@fx41.am4...

I think the arc-shaped scratch on the back wall of the clock, roughly level
with the nut at the bottom of the pendulum, is from times when the pendulum
has not been set in motion truly parallel to the back wall and has scraped
until it has started to swing true. I've not seen any evidence of it
happening all the time, only as an initial start condition.

Oh, by the way, I solved the problem with the camera delaying taking flash
photos. I'd somehow set the flash to red-eye, where it flashes a dim light
on the camera a few times to contract the subject's pupils before firing the
main flash and taking the photo. Without my reading glasses on, the symbol
in the display looked like rear-curtain flash rather the one for red-eye.
Too much technology...

[bert]

In article <MPG.35d25ceaa...@news.eternal-september.org>,
Terry Casey <k.t...@example.invalid> writes

Fascinating. I didn't know that. I'll try it on our clock.
--
bert

[Dave W]

You guessed that the bob might be adjusted by a nut on a screwed rod,
but I can't see any trace of a thread on the rod. Also you said you
don't want to turn the bob, so how can you see the back and say that
it's fixed at its bottom?

It looks as if the whole pendulun might be removed by unhooking at its
top for examination.

How much does it gain in hot weather compared to cold?
--
Dave W

[Dave W]

Further thoughts: The first thing you must do is to tilt the clock
sideways till it ticks evenly.

You said the striking tended to hesitate, which sounds as if the oil
has gone gooey and stiff. Probably the hands also hesitate sometimes,
looking like slow running, but the hot weather has liquified the oil
so less hesitation at present. I suggest a good dowsing in WD40 to
disssolve the old oil, followed by re-oiling with clock oil or maybe
sewing machine oil which might be easier to get. Not '3-in-1' oil
which tends to solidify when the lighter fraction has evaporated.
--
Dave W

[Max Demian]

Aaargh! WD40! You should take it to bits and clean it all - my dad used
petrol - then reassemble and put the tiniest amount of clock oil in each
bearing. (The oil is only held in by surface tension.)

But, since it appears to be working, leave it alone or it'll never work
again.

--
Max Demian

[Terry Casey]

In article <L5G5uMJl...@ghcq.uk>, be...@bert.bert.com
says...

>
> In article <MPG.35d25ceaa...@news.eternal-september.org>,
> Terry Casey <k.t...@example.invalid> writes
> >In article
> ><j_SdneWpwvT69PrG...@brightview.co.uk>,
> >m...@privacy.net says...
> >>
> >> It now runs for a
> >> few minutes, with a tick that starts as a fairly even tick-tock, but then it
> >> starts "limping" - the interval between the tick and the tock becomes longer
> >> than that between the tock and the tick, until eventually the ticking gets
> >> fainter and fainter, and them dies altogether.
> >>
> >That means that the pendulum is no long swinging equally about
> >the vertical.
> >

> >If the clock is wall hung, use a spirit level to get it
> >perfectly vertical and make a small mark on the wall so that
> >you can see immediately if it has moved.
> >
> >Now start the clock and see if that cures the problem. If not,
> >you need to adjust the pendulum's vertical position
> >
> >Move the pendulum to one end of its natural travel range and
> >keeping going slightly further, just overcoming the
> >resistance.
> >
> >Start the clock and listen. Is it better or worse? If better
> >keep nudging the pendulum a bit further in the same direction
> >and try again. If it is now worse, move the pendulum in the
> >opposite direction, again moving it past its natural end stop.
> >
> >Repeat the adjustments until the clock sounds right. All
> >things being equal, it should now carry on ticking without
> >stopping.
> >

> Fascinating. I didn't know that. I'll try it on our clock.

Did you get round to trying it - and was it successful?

[NY]

"Terry Casey" <k.t...@example.invalid> wrote in message
news:MPG.35df8651d...@news.eternal-september.org...

>> >If the clock is wall hung, use a spirit level to get it
>> >perfectly vertical and make a small mark on the wall so that
>> >you can see immediately if it has moved.

Both clocks are longcase, standing on the floor.

>> >Now start the clock and see if that cures the problem. If not,
>> >you need to adjust the pendulum's vertical position
>> >
>> >Move the pendulum to one end of its natural travel range and
>> >keeping going slightly further, just overcoming the
>> >resistance.
>> >
>> >Start the clock and listen. Is it better or worse? If better
>> >keep nudging the pendulum a bit further in the same direction
>> >and try again. If it is now worse, move the pendulum in the
>> >opposite direction, again moving it past its natural end stop.
>> >
>> >Repeat the adjustments until the clock sounds right. All
>> >things being equal, it should now carry on ticking without
>> >stopping.
>
>> Fascinating. I didn't know that. I'll try it on our clock.
>
> Did you get round to trying it - and was it successful?

For the very old grandfather clock about 7 feet tall, I tried that. I can't
feel any change in resistance as I move pendulum aside as far as the side of
the case, which is obviously the limit of its travel. I wonder if the
mechanism is so old that it doesn't have automatic adjustment.

Maker dates from early 1800s (Barwise Mitchell, Cockermouth) and may not
have had any enhancements since then.


For the much newer granddaughter clock (about 4 feet tall), the pendulum is
about 3" long and consists of a bob that hooks onto a vertical piece of
springy metal that nudges the escapement feed sideways. This moves with the
same resistance as far as a hard limit, beyond which the escapement release
doesn't move any further and the spring metal pivots about the escapement
release mechanism rather than about the suspension point of the springy
metal which is slightly higher.

Pressing and holding the springy metal on one side of its hard limit doesn't
seem to alter the neutral rest position of the bob or the even-ness of the
tick and the tock. The clock runs for a few minutes and the ticks get
fainter and fainter until the clock stops. The hands do go round. The
mainspring (and chiming spring) are both fully wound and the mainspring
winder definitely won't go any further, so it's not broken and winding
forever without tightening the spring.

The clock seems to be fairly sensitive about its fore/aft angle. Against the
wall it stops but pulled out a few inches it has been running for about ten
minutes and the tick sounds more even. I wonder if that's what the problem
was. I'll find a spirit level and see how vertical it is fore/aft and
side/side.

[Dave W]

Up to now it's been about your grandfather clock, but now you also
mention a granddaughter clock. Regarding the original one, I don't
understand Terry Casey's suggestions. Perhaps he's trying to bend the
flexible strip at the top of the pendulum, which might have the same
effect as tilting the whole clock sideways by a wedge underneath.

Making the clock vertical by plumbline or spirit level is no guarantee
that it will tick evenly. so I recommend you try my tilting
suggestion.

I did post that on 07/08/18, but unfortunately the title got prefaced
by Re:Re: and shows up outside this thread, so maybe you didn't see
it.
--
Dave W

[Dave W]

On Thu, 16 Aug 2018 15:38:40 +0100, "NY" <m...@privacy.net> wrote:

Up to now it's been about your grandfather clock, but now you also
mention a granddaughter clock. Regarding the original one, I don't
understand Terry Casey's suggestions. Perhaps he's trying to bend the
flexible strip at the top of the pendulum, which might have the same
effect as tilting the whole clock sideways by a wedge underneath.

Making the clock vertical by plumbline or spirit level is no guarantee
that it will tick evenly. so I recommend you try my tilting
suggestion.

--
Dave W

[Dave W]

[Terry Casey]

In article <3tudnSzq87
_bEejGnZ2dn...@brightview.co.uk>, m...@privacy.net
says...

>
> For the very old grandfather clock about 7 feet tall, I tried that. I can't
> feel any change in resistance as I move pendulum aside as far as the side of
> the case, which is obviously the limit of its travel. I wonder if the
> mechanism is so old that it doesn't have automatic adjustment.
>
> Maker dates from early 1800s (Barwise Mitchell, Cockermouth) and may not
> have had any enhancements since then.
>

Any clock I've had any contact with has had a slipping clutch
arrangement to couple the pendulum to the escapement - just a
screw with a fibre pad on the end. Possibly the screw has been
overtightened or the pad has 'glued' itself to the escapement?

This is easy to get at with a mantle clock because the back
door opens, giving access to the movement. You would hve to
remove the movement in this case to check and rectify the
problem.

>
> For the much newer granddaughter clock (about 4 feet tall) .

>
> The clock seems to be fairly sensitive about its fore/aft angle. Against the
> wall it stops but pulled out a few inches it has been running for about ten
> minutes and the tick sounds more even. I wonder if that's what the problem
> was. I'll find a spirit level and see how vertical it is fore/aft and
> side/side.

Assuming the wall is true, you can replicate the same effect
by loosening the movement fixings and putting suitable packing
detween the bottom of the movement and the case. Over a
distance of nearly 4 feet, the thickness of the packing will
be only a minute fraction of 'a few inches' to create the same
angle and shouldn't be noticeable under normal operating
conditions.

[Terry Casey]

In article <66sbndd4eavpshbno...@4ax.com>,
da...@yahoo.co.uk says...

>
> I did post that on 07/08/18, but unfortunately the title got
> prefaced by Re:Re: and shows up outside this thread, so
> maybe you didn't see it.

I don't recall seeing it but I don't think there will be any
doubts this time!

[Johnny B Good]

On Fri, 03 Aug 2018 20:31:39 +0000, Johnny B Good wrote:

====snip====

>
> Checked my desktop's clock just now against Time.is
>

====snip====

>
> "Your time is exact!
> The difference from Time.is was +0.000 seconds (±0.044 seconds)."
>
> That's via Opera's VPN. I'll turn off the VPN and try again.
>
> "Your time is exact!
> The difference from Time.is was +0.012 seconds (±0.026 seconds).
>
> That's about what I'd expect having eliminated the extra latency of
> Opera's VPN service. It also confirms that my 13 year old Casio Data
> Bank 360 watch is still one second ahead since the last time I had to
> rescue it from January the first 2000[3] a week or so back.
>
>
=========================================================================
>
> [NOTES]
>

====snip====

>
> [3] It has the best thought out digital watch display I've *ever* seen
> but after 9 years of faithful service, just as it had finally settled
> down to an accuracy of +/- 1 second per annum, it took to blanking out/
> resetting itself to the 1st of January 2000 every few months or so.
>
> The last time I had to rescue it from its brief sojourn in the past,
> the
> 'shock' of the 'rescue' was so severe, the pin holding the retaining
> toggle on the adjustable clasp of the stainless steel bracelet jumped
> free. Luckily, I was able to find it and reassemble the clasp.
>
> I really aught to replace it but the only digital watch that comes
> close
> to the display ergonomics of my quirky Casio is another DB360 and the
> only sensibly priced sources seem to be Ebay traders so I've played my
> strong suite and procrastinated like crazy - it's what I do best.

=========================================================================

Follow up on that note:

It seems procrastination *does* pay after all!

Whilst on a fortnight's cruise to the Canaries earlier this month, I
managed to purchase another Casio DB360 in Gibraltar. I'd spotted a
similar (not exact and in black) Casio in the window of a small
electronics shop in Main Street (Jaya Bazaar) so went in to have a closer
look.

Whilst chatting to the proprietor about my desire to purchase another
DB360 to replace the rather battered example I was wearing, he told me he
thought he might have that exact model in his stock room and went off to
check, returning with a brand new boxed DB360 (complete with ~250 page
-40 in English- instruction manual booklet).

Talk about serendipity! At a mere £32.95 (Sterling), I couldn't resist
the opportunity to purchase a watch I'd been able to handle and verify as
a fully functioning "Real Deal"(tm) item. Never mind the 'Travelling
Costs' (that was a sunk cost anyway), it seemed a much better risk than
paying an eBay trader a similar amount and keeping fingers crossed that
I'd actually receive a brand new unused (if rather old stock) Casio
DB360. :-)

The *only* difference[1] between the original and the new watches being
their countries of manufacture - Malaysia (old) and China (new). Apart
from that (and the wear and tear on the old), they're otherwise
identical. It's funny how things work out, given enough time.

BTW, checking against the time.is site with the browser VPN disabled, I
get the following:

Your time is exact!
The difference from Time.is was +0.011 seconds (±0.027 seconds)

With the browser VPN enabled, I get this result:

Your time is exact!
The difference from Time.is was +0.003 seconds (±0.048 seconds).
Time in London, United Kingdom now:
00:34:25
Saturday, September 1, 2018, week 35
Sun: ↑ 06:14 ↓ 19:47 (13h 33m)


[1] If you ignore the fact that the new watch seems to have gained ~6
seconds in the past 16 days since I bought it, compared to the ~4 seconds
gained by the old watch since I stopped wearing it.

I've never worn any watch to bed as a rule so my watches have always
been subjected to some level of daily thermal cycling (even with my first
LCD watch, a Sekonda with a display that blanked out at low room
temperatures!).

--
Johnny B Good