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John Wildings great wheel skeleton clock

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Andrew Read 109/09/2018 18:09:42
11 forum posts

Hi, I’m completing my 1st clock John Wildings great wheel skeleton clock, it’s built and I have had it running for periods up to a week before it stops, I’ve re cut wheels that I thought were the issue and I think I’ve now narrowed the problem to the meshing of the centre wheel and 3rd wheel pinion which I just can’t seem to get right, if I spin the 3rd wheel and centre wheel in the frames they run well with no resistance but once the complete clock is assembled and wound 2 or 3 turns when it stops it’s always where a pinion leaf is just entering the centre wheel. Can anyone advise on what I may have missed or some way of checking the meshing, the wheel is cut 0.6 module and I brought the pinions from Ian T Cobb.

Neil Wyatt09/09/2018 18:52:12
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Have you tried marking the teeth with a dot of tippex to see if its the same tooth or even the same pair it sticks on?

It cold be one very slightly out-of spec tooth that's causing the issue or something like both gears very slightly eccentric and sticking when the two high points coincide. Everything changes when gears are under load, I know from experience, though not with clock gears.

Neil

Marcus Bowman09/09/2018 23:05:27
148 forum posts

I have not made one of these clocks, but can offer some suggestions arising from experience with other clocks.

I suppose you have tried testing the gear train with the clock assembled, but without the barrel or the escapement?

That way, you can apply gentle pressure and see and feel what is going on under gentle power but without the force applied by the spring. It's also quicker than waiting a week for the clock to stop.

As Neil says, it is a good idea to mark the offending teeth of pinion and wheel if you can identify them when the sticking occurs. Try it a few times. If it is always the same teeth, they can be given individual inspection and attention.

Is there an eccentricity caused by the seating on the wheel collet? It is always a good idea to finish turn the collet after it has been secured to the abor, before attaching the wheel.

If you know which tooth of the wheel is definitely causing the problem, I would recommend burnishing the face of the tooth before reaching for the file. Next in line would be the tip of a triangular scraper, followed by the burnisher, before reaching for the file.

Did you make the little depthing tool to J.W.'s design? It's quite handy. Not big enough for the great wheel, of course.

Neil is also right about the changes in meshing when the gears and arbors are under load. Skinny arbors tend to deflect under load.

Marcus

Andrew Read 110/09/2018 20:34:57
11 forum posts

Thanks Neil, Marcus, will have another look and see what I can find. I did make the JW depthing tool. Is it ok to treat the pinion in the same way as the wheel you mention above with burnisher in case it’s more than 1 tooth causing the issue? The disappointing thing is the depthing of the pinion and wheel looked good in the depthing tool

Marcus Bowman10/09/2018 22:38:32
148 forum posts

I would hesitate and have a cup of tea before removing metal from the (steel?) pinion. It may be that the pinions were supplied with a final polish, but, if not, I would certainly polish the leaves using a piece of approximately-shaped wood and some fine abrasive powder. Wilding recommends ~"coarse oilstone dust" in one of his other books. I think a more modern way would be a finer grade of diamond paste. Rub along the gaps between the teeth. Once satisfied, move to a finer grade. JW recommends Solvol Autosol, and that's as good as any for a final polish once any marks have been removed.

I might also try my luck with the arbor suspended in vee blocks and a DTI with an elephant's foot against the tips of the leaves, to see if you can measure any eccentricity. I suppose you could do this in-situ, if you can secure the frame and the DTI so that they do not move relative to one another. You could repeat this with the mating wheel. I understand that clockmakers of yore used a 'topping tool' to ensure the tips of the teeth were all at the same distance from the centre of the wheel.

Forgive me if I grasp at a few more straws:

I assume you burnished the pivots at the ends of the arbors. Those need to be well-finished and burnished to harden the surface. The shoulders where the pivots step back up to the full diameter of the arbor should be finely finished, and undercut if possible. A watchmaker would polish the faces of those shoulders. The inner edges of the bearing holes in the plates should have a really tiny chamfer. The idea is that the pivot shoulder cannot seize against the corner of the hole. The bearing holes themselves should have their inner surfaces burnished, to harden them and reduce friction. I know you probably did all that, but those are sources of additional friction.

You say the train runs freely under finger-power. How freely? It should coast for a long time, if there is nothing to impede its progress. What happens if you tilt the clock while the train is spinning freely? Same if you tilt it the other way?

Marcus

Marcus Bowman10/09/2018 23:12:10
148 forum posts

Another thought about sticky teeth (more straws to grasp at):

When the clock stops, is it possible to apply just enough additional (small amount only, of) pressure to move the teeth past the sticking point? If so, you may just be able to see a polished high spot around the tip of the wheel. Burnish that, or scrape and burnish. I have a daisy wheel mechanism I make quite often for the motion work on skeleton clocks, and I know that spotting high points in this way can help. It is quite tricky, though. And almost impossible if you have carefully burnished the acting faces of the teeth. Felt tip pens are sometimes useful here. You would expect the ink to be rubbed off each tooth in the same way, so any obvious differences indicate a problem. One thing worth saying is that one turn of the pinion or one turn of the wheel is unlikely to give you all the meshing combinations of leaves and teeth, so many turns may be required before the troublesome combination occurs.

Second thought is that it might be worth making sure all is ok with the barrel and spring. Springs sometimes rub inside the barrel, and that can make the clock stop once the initial kick from the spring has passed, and the spring is exerting a lower torque. Rubbing would tend to leave a scrape in one barrel end. If it is a strong spring, you may find the problem is with the barrel pivots binding under power.

Is the motion work behaving, or is there friction in the hands or pipe assembly? There are lots of parts in close proximity there, so there is lots of scope for friction.

Marcus

Andrew Read 111/09/2018 14:19:08
11 forum posts

Hi Marcus, really appreciate your response and to answer the points you raise, yes all pivots have been burnished and when the clock runs the recoil at the escapement is good so I think the friction is minimal at the pivots, I have also cut the tiny chamfer at the pivot holes in the plates. When I fit just the centre wheel and 3rd wheel it spins well under power from my finger and runs down and stops eventually however last night I put some resistance on the third wheel as I also moved the centre wheel and managed to get the pinion to but I think on 1 of the 3rd wheel teeth, if this is repeated and the wheels are just spun they run freely, the depthing as I said looks good so I'm at a bit of a loss with this problem, I will try to find if more butting is occurring when I can get back into the workshop

Andy

Martin Kyte11/09/2018 16:41:17
1335 forum posts
9 photos

By your description "just entering the centre wheel" the depth of engagement may be a tad to deep. Most of the action is supposed to hapen after the line of centres when wheels drive pinions to ensure no wedging action can occur. If you do decide that this is the problem you could bush the pivot hole and re depth the offending arbour. Don't do anything until you are certain of the problem. You are really the only one who can diagnose the issue as you have the clock in front of you. We are only in a position to say what it might be.

regards Martin

Andrew Read 113/09/2018 13:01:54
11 forum posts

Ok thanks for the suggestion Martin, will check and have a cuppa tea before assuming anything

regards Andy

Andrew Read 118/09/2018 20:56:39
11 forum posts

Neil, Marcus, Martin, thought I would let you know I’ve looked at the points you made and it looks like I needed to polish the pinions as once I looked at them they were really quite rough, I’ve now polished them and the clock is running again and running well. Thought I would just drop you a line thanking you for your help

Regards Andy

Marcus Bowman18/09/2018 22:34:19
148 forum posts

Glad to hear your clock is up and running sweetly now. You can count that a success.

What’s the next project...?

Marcus

Andrew Read 119/09/2018 08:49:03
11 forum posts

Hi Marcus

I have the plans and most of the materials for the Strutt Elliptical clock, not sure how difficult a build it will be but we will see, there are fusee's involved which I have never made although have always wanted to make 1

Was surprised that the pinion polishing was not mentioned in the John Wilding book on the large wheel Skeleton clock or that I haven't read about this before but will know next time to check

What clock projects have you worked on?

Marcus Bowman20/09/2018 08:29:50
148 forum posts

Andrew,

The Strutt is an interesting clock. I have the Bill Smith book on that one, and I have seen several completed clocks, some original and some made from the Smith instructions. Smith's book refers to the photos of a Strutt in Royer-Collard's book "Skeleton Clocks", but I see better photos of a wider range of Strutt & Wigston epicyclic clocks in Derek Roberts' book "British Skeleton Clocks" (Wigston was an engineer, and business partner of Strutt, so I imagine Strutt was the designer, but commercial manufacture was arranged by Wigston). I have seen instances of completed Strutts at verious ME exhibitions, and I think I recall seeing one a couple of years ago in the collection of the Worshipful Company of Clockmakers, held in the Science Museum. The interesting part of the machining of the Strutt is the cutting of the internal teeth of what Smith terms the ring gear.

I built a Wilding 16th Century one-handed clock with a verge and foliot escapement, as it was serialised in the Horological Journal in the late 1970s. I can still remember quite clearly the moment I got it to run, so I can imagine your ow joy with your current clock. I have a Widling Congereve almost clomplete, on the bench at the moment. I have built a number of skeleton clocks which originated from a Wilding design and are based on a pigeon timing clock. My plan was to start with the Wilding modifications and make some changes as I went through a series of those. The clock features a daisy wheel mechanism in place of the conventional motion work. After the first one, which was fairly close to the Wilding design, I made some significant departures from that design, so that the whole motion work is now quite different (although still based on the daisy wheel). The clocks also feature a prominent platform escapement, so I have had to learn how to deal with issues concerning springs and rating. Other parts of the original design have now been progressively modified, so that the whole thing is now rather different. That was the idea behind the 'series' of clocks, and although it has quickly taken me in directions I had not anticipated, I have enjoyed the journey. Along the way, I have been unable to avoid a constant stream of repairs to (mostly) longcase and wall-hanging clocks, and cuckoo clocks (which I find bring a smile...), all of which brought valuable (and sometimes hard-won) experience. And I have a design for a wall-hanging clock which I am almost ready to start making. That's if I can get the next 3 skeletons off the bench, and get the Congreve finished, polished and into its Perspex case. Interestingly, Wilding recommends polishing the pinion leaves, in the Congreve book (and others) but it is a technique explained in a number of general clockmaking and repairing books, so I am surprised it is not in the Great Wheel book. Polish; harden; re-polish (or at least clean after hardening).

I can recommend membership of the British Horological Institute, and its journal, as well as branch meetings of like-minded souls who are a constant source of good advice. They run good courses as well, at their headquarters. There is also a distance learning course which can be done at your own pace.

Marcus

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