Basic Clock Design

The Brocots:

Slides 26 and 47 of this presentation are interesting !!

MichaelG.

Edited By Michael Gilligan on 30/04/2016 22:36:20

Reading through the comments about Brocot escapements and looking at the pictures, I can see the benefits of them, especially with regards to construction. Are they used in clocks with a 1 metre ( 1/2 second?) pendulum? From slide 26 inthe linked presentation, I am not clear.

James.

Neil's post of the animation is the most interesting and most useful, and am surprised no one has so far commented on the lack of slight recoil on the animation.

I think some of you are making things far too complicated and technical, and going way off topic.

The essential basics when designing a clock/choosing what design are the parameters of timekeeping you are expecting.

There is a great deal of satisfaction every weekly wind not having to alter the hands, though if this is required if the clock is slow it takes a few seconds, and if fast perhaps a bit longer. If this alteration doesnt bother you then some of the discussion here is somewhat barmy.

I have had 30 odd years experience of dealing with tower/turret Church/public clocks. Some of these were 'modern' Victorian flat bed clocks, and some were far more rudimentary and earlier. The most problematic clock is that fitted in the 1960s to St Johns Church Cardiff made by Gillett and Johnston with Grimthorpe double beat escapement and automatic winding. It regularly stops for no apparent reason whatsoever. I have a view on the cause of the stoppages, though this is somewhat 'off topic' as per perhaps some posts above!

Cheers,

Julian

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Julian,

Not that it matters ...

1. "Neil's" animation is simply the one that I linked earlier ^^^
2. Timekeeping is a complex and interesting subject ... we are only scratching the surface here
3. On the last occasion when you "told us off" I explained my position regarding "Basic Clock Design"
4. Earlier today, James specifically asked me to continue posting

MichaelG.

More or less yes Michael. There is rather a lot on escapement efficiency on Abbyclocks including the dead beat. I am thinking it's a red herring. I'll have a look at the presentation later.

I don't see why a Brocot shouldn't be used on a 1m pendulum however tiny jewelled pallets might not be appropriate. I'll see if I can dig out some details on the pin size of one that uses something similar.

Julian seems to be unable to accept that some might want to make a rather accurate clock or that in real terms most additions are no harder to make than those in a simpler clock however he has a point on recoil but perhaps he could explain why there will be some.

Anyway as it was mentioned - by me sadly, Julian may not like that, this is the pin pallet.

Note again slight recoil comment but this is still a recognised dead beat. The reason I took some notice of it was the number of clocks I have had where those super fine escapement wheel tips have bent. Pretty easy to straighten again but it shouldn't happen. This one uses the wheel tooth top slope for the impulses. I get the impression that many clock makers don't like it - cheap watch technology. The Brocot is easy to manufacture too.

John

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Edited By Ajohnw on 30/04/2016 23:59:09

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... Mmmm ... Let's think about this ....

Maybe the lack of recoil is why it's called a Dead-Beat Escapement.

MichaelG.

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John Reynolds is using one in his [New Design of] Regulator ... serialised in both 'Horological Journal' and 'Engineering in Miniature'.

MichaelG.

Michael,

Thank you. Whilst I found it relatively easy to draw the pallets shown in my design, I do have doubts about my ability to accurately shape them in practice. The Brocot design, with its pins, seems to avoid the problems that I had envisaged with my design.

Back to the that part of the drawing board....... which is why I asked in the first place: to avoid as many pitfalls as possible.

Regards,

James.

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Julian,

I cannot speak for the other contributors, but:

I would be genuinely interested to know more about the clock, its problems, and your theory ... either on this thread, or perhaps a new one.

I couldn't find a picture of the St John's Church clock

... Is is something like this one ?

MichaelG.

As I pointed out in an earlier post, the diameter of the Brocot pallet is made equal to the tooth pitch of the escape wheel less the drop. So there is no problem with tiny jewelled pallets, just make the whole thing bigger to suit. Fully hard silver steel on brass has about the same coef. of friction as ruby on brass, perhaps just a little less hard wearing but it should last 100 years or more! My sister has a long case clock made by our great great grandfather about 175 years ago and it is still going strong with no jewels.

Russell.

Interesting photo MG. One wonders about the mentality of some people (referring to photo) that thought it a good idea to put the electric timer underneath it and 2 ft off the ground instead of beside it and a comfortable height.

Bazyle,

It may possibly be more intelligble in context: **LINK**

MichaelG.

The pins on a 2 sec period pendulum design I have are 0.095" dia and some one ran the clock with a 20lb bob on the pendulum.

Michael's presentation link is interesting - nearly dead beat, well they all are but big swings is worrying. That suggests a big impulse angle but the escapements he made were generally tiny. Escape wheel size and the centre distance between the escapement and wheel has an effect on this. If the pins stays the same size the impulse angle reduces as the wheel and spacing gets larger. This also has an effect on the angular effect clearances have, None of them can be made perfectly.

This is probably going to be tough going as it concentrates on the Graham but explains all sorts of things and how all dead beats relate so the Brocot design is all over the place.

**LINK**

I have my doubts about the efficiency arguments who ever wrote it but that's me. Theory is fine but often practice is different and theory turns into scotch mist.

John

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The reason for jewels Russell is the wish for no oil at all anywhere. But I would want to make sure it works first. They aren't cheap. This might start a debate on oiling jewels but I'll try the one that goes don't.

Whoops - I meant to add thanks Russell. That gives me a nice easy way of viewing the impulse angle.  Calculating what it is precisely may be a bit tough.

John

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Edited By Ajohnw on 01/05/2016 11:25:58

John [and James]

May I recommend that you look at Part_2 of John Reynolds' series

[February 2015 in HJ ... possibly available via your Public Library]

He covers the design and construction of his Brocot escapement quite succinctly.

MichaelG.

Thank you for the suggestion. I know that, unfortnately, it is not available at our library. I shall contact the Horological Journal to see whether it is possible to buy a back-copy.

James.

I think I can cope Michael. As I am aiming at a pendulum with a 1/2 sec beat I have a choice of tooth counts and hence wheel size plus the point Russel made. The impulse angle is formed by 1/2 the dia of the pallet at the angle it's presented.

What is clearer on Niel's animation is what happens when the pendulum swings further than the impulse angle which I think is the whole idea of the Graham. Next thing to look at and why the pdf I linked to suggests examining their behaviour at several angles. Maybe Russell can comment. The impulse on the Graham is provided at an arc at the centre of the swing.

John

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Alternatively ... I understand that the EiM series was launched about six months behind the HJ.

[not sure if the publication sequence is the same though]

MichaelG.

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Delighted to hear it ... and I look forward to seeing it.

Are you planning a compound pendulum, or do you have a convenient tower in which to install the clock ?

MichaelG.

A 1/2 sec beat pendulum works out at 248mm Michael - assuming the sums are correct this time.

B'ham library doesn't keep copies either, nor EiM. I do have several books with details of the Brocot in it but none so far really provide an answer to what happens when the pendulum continues to swing in what ever direction it's being impulsed in which it will tend to do. All make the point about the tangent and mention dead beat. I'm hoping Russell or some one can shed some light on that.

I can't edit the earlier post. The length of the arm also influences the impulse arc, longer --> shorter arcs.

Might be worth adding that the GIMP  can be used for animations. A bit tedious though but images can be rotated down to 1/10  of a degree so  there is enough resolution once the parts are drawn.

John

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Edited By Ajohnw on 01/05/2016 16:09:19