Duncan,

Given that a quartz clock is just about cheap enough to give away in a box of cornflakes, I think any rules you care to make for a pendulum clock are valid. For myself, I am aiming for a couple of NE555 timer delays and some LEDs to check the timing. If possible I want to dispense with optical swing sensors and use the induced voltage from the remnant magnetism to control both the amplitude of swing and timing of the pulsing.

I too was thinking about using waste heat to stabilise the clock temperature, bimetallic powered louvres perhaps. But that still leaves the barometric pressure compensator unless I partially evacuate or pressurise the cabinet.

I'm going to have to start cutting metal soon!

Colin

Russel,

I plan to drive a counting wheel from the pendulum so I guess the Q will come down a lot. Extracting energy without introducing a pseudo escapement error could be fun but I'm looking closely at the techniques used in MORT.

Martin,

I can always drop the drive voltage or add a resistance in series with the coil to reduce the impulse. But if the electromagnet pulse is too small it can't easily be boosted.

As I don't want to build mutliple iterations of the clock I plan on giving myself a very generous overkill on the impulse.

And the good news is with the latest iteration of the magnetic circuit and a few bugs fixed in the spread sheet the balance point is a lot less sensitive to orders of magnitude changed in mu r.

Still, at the moment it looks like I have a 1kg copper coil that's over a kilometre long so I may try some shorter versions and only increase the coil size if I can't maintain the oscillations.

Cheers all.

Martin,

The following chart shows how the force in Newtons picks up as the pendulum closes the air gap between the two pole pieces. (The x axis shows the distance between the pole pieces in cms.)

Integrating the area under the curve shows that a balance point exists ( y = 0) with equal impulse before and afterwards this point on the x axis. This balance point should correspond to the bottom of the pendulum swing if the escapement error is to be zero.

The electromagnet should deliver around 1/3 of the energy in the pendulum with a 12V power drive. This is probably too strong but it will allow the voltage to be lowered or the excitation time shortened,

Colin

Thanks all.

Hot rolled steel is probably a good description. I can take it from there.

Hysterisis or remanence is no big deal at pulsing rates of 1 cps or so I believe. In fact a bit of remanence is highly desirable so I can use an induced voltage on the return stroke to monitor the amplitude of the swing and provide the timing for the next power swing.

Cheers, Colin

I am planning to make an electromagnetic mandrel, some yokes (shaped pole pieces) and a pendulum bob from something called black steel in Thailand. This steel is available in large sheets of varying thicknesses and can be plasma cut for pennies.

The idea is to use an electromagnet to impulse a steel pendulum bob with zero escapement error and the magnetic forces essentially tangential to the arc of the pendulum swing thus keeping g at 9.81 m/s/s.

My modelling suggests that the location of the centre of impulse from the electromagnet (needed to take the escapement error to zero) is a function of the magnetic permeability of the steel used, hence the query.

Can we please not make a silly situation worse? There are already concerns about 'never adding water to acid' - but this advice applies to only one acid, which we have here - sulphuric acid. BUT - and it is an important BUT - the advice applies to CONCENTRATED SULPHURIC ACID. ONLY.

Based on my experiences with concentrated hydrochloric acid with a pH of -1 I would remove the word Sulphuric from the above advice, i.e. any concentrated acid should be added to water and not vica versa.

Anyone else here have the title of European Engineer (Eur. Ing.)? It never did really catch on in the U.K.

Eur. Ing. Russell

The UK Passport Office recognises the title Eur Ing and because the European Federation of National Engineering Associations, FEANI, which issues the title is unconnected with the European Union the use of the prefix within the UK will survive the end of the Brexit process.

Just to annoy the Brexiteers, I and a number of others plan to add the prenomial Eur Ing to our passports when they next come up for renewal. (I know, it's petty, but there's not much else you can do.)

Eur. Ing, Whittaker

Martin, My last experience of working was in a dual ladder organisation where as an engineering advisor I was often paid more than my manager. It worked well, at least for me, but I don't know how common this structure is/was and whether it now survives in my old oil field service company now that the head count has dropped by 50%.

There are a suprising number of Martin Kytes on LinkedIn. Are you the one in York?

As a happily retired professional engineer living in Thailand I sometimes browse the job vacancies in the UK to see what I could turn my hand to if I decided to return to the UK. However, it seems that any job vacancies that include the word engineer are almost invariably never for professional engineers and any job vacancies for graduate engineers are for the newly graduated. What job description should a professional engineer that doesn't wish to be a manager look for?

In the UK if a male visitor introduces himself as an engineer the householder's response will often be to enquire whether he can take a look at the washing machine that is acting up. In Germany the same householder would rapidly introduce his unmarried daughter.

Sounds like I do have the real thing.

Thanks for the intelligent answers to my stupid question.

I guess I'd better give my supplier some positive feedback.

Cheers, Colin

It's only cost me a few dollars so it's no big deal ...

I decided to buy some spot drills for use in making accurately located holes in brass for a clock. The set of Chinese bits that arrived from AliExpress do not come to a conical point as I would expect. From one side the bit does come to a point but when rotated 90 degrees there is now a large flat profile that doesn't look as though it will deliver the wanted hole precision.

Who's confused about what a spotting drill should do/look like? Me and/or the Chinese supplier?

Thanks, Colin

A few years back and with a a bunch of students who comfortably post-dated metric money the following question came up on University Challenge,"What was the price on the mad hatter's hat in Alice in Wonderland in metric money?" And one of them still beat me to the answer.

In the early 1990s on a Japanese Oil Rig in Nigatta Prefecture I thought I had picked up a tape measure using decimal fractions of a foot. A day later I realised I had discovered a new a new unit of measurement, the kanejaku, when all of my depth log measurements started to appear slightly off depth with each other.

Marcus,

The Science of Clocks and Watches arrived and I've now finished it. OK I slid over some of the mathematics but I really enjoyed the graphical explanantion of why late or early pulsing of an escapement alters the regulation. I'm only sorry I had to encounter the cgs system again.

I guess I have all the books on horology I need now, well maybe just one more, Accurate Clock Pendulums by Bob Matthys, once I can justify 87 GBP for it (thanks John Haine).

Best regards, Colin

Duncan,

Yes it is too late but thanks for the offer.

On the other hand I am saving up for "Woodward on Time", it's currently available for $106. You can't help me out there can you?

Cheers, Colin

Marcus,

Thanks for the early, long and considered reply; I've placed an order for The Science of Clocks and Watches.

My feeling is that most practicing horologists couldn't explain why the amplitude of a pendulum swing stabilises or know where to find out why it doesn't continue increasing until it hits the wooden case or seriously damages the escapement. The only book I've found that covers this aspect is MORT by Woodward. Compare this to the case of steam or internal combustion engines where most practioners are again following a recipe to get a working engine but there is an immense field of scientific/engineering theory underlying these engines which is relatively easily accessible.

So we end up with a craft that develops its own technical vocabulary (wheels versus gears for example) and abhors the new; are not ball bearings the work of the devil?

I must not say more as, at present, I am no more than an armchair clock designer with plans that have worked perfectly while they stay in my imagination.

Thanks again, Colin

Since receiving a copy of Woodward's "My Own Right Time" a week ago I have read the book from cover to cover, twice. Are there any other publications out there that cover Horology in the same detail? And are the majority of professional clock makers just skilled artisans that have no idea of the mathematics and physics of why they do things?

(I took 10 minutes carefully drafting the above paragraph but I still know I'm going to get flamed.)

Colin

I could start a new topic but I think this one is a better start.

Has anyone heard of the daisy wheel motion of Wilding's take on the Woodward clock being doubled to not only deliver hours from minutes but also minutes from seconds? I'm guessing it's theoretically possible but it may be impractiacally complicated.

Why am I asking? I'm wondering if a free pendulum could drive a second wheel and hence a minute and an hour hand via two concentric daisy wheels.

Thanks, Colin

Neil,

I want to find the article that this post refers to.

A search of the www.model-engineer.co.uk website delivers the following, see below.

How do I find out where the article is?

Sorry if this a dumb question asked and answered too many times before.

Colin

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