Member postings for Marcus Bowman

Colin,

One of the books I have, to which I find myself returning at intervals, is one of Derek Roberts' volumes: Precision Pendulum Clocks - France, Germany, America, and Recent Advancements. This contains little theory, and is too expensive as a casual purchase, but it contains many good photos of mechanisms, particularly the pendulums, suspensions and other details of the later fine timekeeprs by Reifler, Fedchenko; The Littlemore clock, and it has a chapter by Philip Woodward. There is much joy to be had just savouring the fine craftsmanship. Examples of many of the mechanisms can be seen at the Royal Observatory.

Another book I see mentioned from time to time, and again in this month's Horological Journal, is The Theory of Horology, by Reymondin, Monnier, Jeanneret and Pelaratti, published by the Swiss Federation of Technical Colleges/WOSTEP with the latest edition dated 2015. I am not convinced you would find enough about clocks in the book, or enough about heavy theory, as the description says more about watches. Fearfully expensive, but a book that has been around for a long time. I do not have a copy on my shelves, as my pocket money won't stretch that far.

Marcus

Looks like a C to me. Lathes.co.uk says 'A (gearbox and power feeds), B (changewheels with power feeds) and C (changewheels and hand-cross feed) ' and that accords with my own experience.

The leadscrew engagement handle also tells you something about the age (black plastic on the much later models), as does the position of the backgear change handle (top of the headstock on much later models). The thickness of the base of the cross-slide indicates whether the lathe is 4.5inch or 5inch centre height.

Serial number (often at the right hand end of the bed, stamped into the front bed way, should also tell you (at least on the underdrive machines, but I imagine on the others too).

There are different bed lengths.

Marcus

Woodward wrote 'Woodward on Time' (WOT) which is excellent. However; I don't have 'My Own Right Time' (MORT) and suspect there is some overlap. WOT contains all of Woodward's articles, mostly published in the Horological Journal (monthly journal of the British Horological Journal). You will find much of interest at the level you seek, in the BHI Journal. Membership is not cheap, and the Journal does not have a huge number of pages (about 44 pages per issue), however; it is the place where you will find the most relevant information and articles, both practical and theoretical (reflecting the craft/theory balance typical of the way horology has developed.

The USA-based National Association of Watch and Clock Collectors (NAWCC) are worth a look, but once a member you may also opt into the Horological Science Newsletter, which will more than satisfy any desire you might have to delve into theory. I have found them to be an excellent and very helpful source.

There are lots of books dealing in a serious manner with particular aspects of clocks and watches; and some of those contain some theory. Many contain an in-depth review of a particular kind of clock, and some contain associated musing s on the theory. There are also lots which review types of clocks but do not delve into theory at all. All are expensive (a trait of horological publications of any size).

I believe the craft/theory balance is represented by Wilding and Woodward. John Wildings books are tremendous if you want to make a clock but are not bothered by theory; while Woodward never intended to be a maker, but was interested in the theory. Both have helped take us forward, and both are necessary components in the development of theory. That craft-then-theory path represents fairly typically the way horology has developed since its beginnings. I do believe, though, that the subtle underlying physics are just that - subtle- and most people looking at, or even repairing a clock or watch do not fully appreciate the influence of physics on the physical article, or the theory brought into action in a clock. That's not just true in horology, of course.

Woodward's most important practical work, based on theory, was W5, an impressively accurate clock completed in 1985, and detailed in MORT, I believe. WOT contains a chapter entitled 'A Fresh Look At W5' (first published in Horological Science Newsletter). There has been a lot of interest in that clock, and the underlying theory, and it has been subject to some important development, since the WOT book.

One or two other titles from my bookshelf:

The Science of Clocks and Watches (Rawlings)

Clock and Watch Escapements (Gazeley)

Wheel and Pinion Cutting in Horology (Wild)

One of the conundrums is that early pioneers understood, at least partially, what they were doing, but did not develop the physics or spread the knowledge. The craftsamn protected his own key knowledge, perhpas? That means later studies of the development of particular types of clocks represent an attempt to trace, reveal, and understand the early knowledge (a kind of knowledge archeology perhpas). So there are interesting strands of theory in many of the serious horological books on particlat clocks. Synchronome, by Miles, for example, survays the life and works of Synchronome and his clocks, but also contains clear and well expressed explanations of the theory and practical realisation on which the clocks are based. So a further list perhpas depends on the kind of clock in which you are interested.

I have those kinds of books on Synchronome, longcase, precision pendulum, chronomoeter, musical and electric clocks, which suggests I am interested in the pure mechanics and physics in all clocks and watches, which seems about right. That's the spot that Woodward hits. MORT and WOT being the top of that pile.

Marcus

I console myself with the thought that the annual running cost of a large Paul-Allen-style boat is approximately 10% of its running cost. Paul Allen owns TWO of the world's 100 largest super yachts. Octopus cost $200M and Tatoosh cost $160M, so the annual bill just for his water-borne transport is, er..., enough to keep the economy of a small country afloat.

I have to say that, like Neil, I do rather like those big boats.

That's clearly an aspirational statement, because all my yachts are currently models under 1metre. I need to think bigger.

Marcus

There is an article in Horological Journal dated March 2003 2hich is by Derek Pratt, discussing his double daisy wheel mechanism on one of his sculptural clocks. There is a mention of an earlier article by Peter Hastins in the August 1979 issue, which is seen as a seminal article giving a comprehensive explanation of the daisy wheel and its many variations.

Here's a thought:

I have built several clocks using a daisy wheel arrangement for the drive to the hands. The basic dimensions were taken from a John Wilding design, and he, in turn, took the dimensions from a much earlier article.

When I chased up the source documents, I discovered that the daisy wheel is an inherently non-linear gearing. The time will be correct at some point, but will be too advanced at some intermediate times, and too retarded at others. The variation is dependent on the length of the anti-rotation stalk. I have a relatively long stalk, but the variation is still present.

I had to vary the dimensions of the daisy wheel itself, and then had to experiment with the pin spacing to get it all to work in a smaller size (the problem being that the as-designed size causes the wheel to obscure the winding square, in some positions of the eccentric cam). I couldn't get the dimensions to scale from the original theoretical explanation.

I also find that there is considerable scope for the weight of the hands to emphasize the clearance present in the daisy gearing.

So; an interesting, but deceptively simple solution to gearing the hands.

It does look pretty though, especially if you skeletonize the daisy wheel itself.

Marcus

Water of Ayr stones were produced a few miles from where I stay. Quarrying from the river Ayr was halted many years ago, and as far as I know the stocks are all gone. I still see it listed as available in some places, but don't know if that is the real thing. I have a couple of sticks I use from time to time. It is very soft, and I would suggest too soft for everyday use. I only use it for frosting polished brass plates.

For honing, it depends on the fineness of the finish you require.

600 grit diamond stone, followed by 1200 grit, will give a finish good enough for the faces of a graver for turning steel or brass. Those stones/plates are readily available. For finer finish, a 2000 grit diamond stone or a ceramic lapping stone or wheel used with diamond spray (3 micron, down as far as 1/4 micron). If you need a better finish than that, you better order some strong sunglasses...

Hardened work takes a better polish that unhardened material, so, as with grinding, harden the work before polishing. Yes; unhardened work can be lapped more quickly, but it will not take a really good finish or polish.

Other interesting polishing and lapping compounds include traditional powders and polishes used by clock and watchmakers. I'm not convinced they are capable of giving a better polish than diamond spray, though. I have one or two powders, but use them infrequently.

If you have a lot of lapping/polishing to do, you might look at the GRS Power Hone (try H.S. Walsh).

There are also some useful polishing papers, from the finer grades of emery 0, 0/2, 0/4 etc, and crocus paper.

For plastics, there are micro-polishing fluids and pads which give a terrific finish if you have the patience.

Arkansas stone is worth a look too, but is rather expensive, and, in the end, not any better than diamond; and less effective than the finest grades of diamond spray.

The only real problem with all of this is that a really fine finish takes a little time.

Marcus

I think this is also an issue with other magazines from other companies. I have a digital subscription to another magazine and find the digital copy not half as handy as the paper copy, while the paper copy would come via surface mail from far away and be much more expensive. I will not renew that digital subscription, but, as you found, I think I will lose the ability to access the digital copies.

So it seems as though we buy access only and not actually a copy of the magazine.

For the magazine to which I subscribed, I have already decided that the content is not worth the continued subscription, so that solves the problem.

This, of course, is the software subscription problem, where software companies are moving rapidly to a subscription basis where you get to use the software, but only as long as you pay the monthly subscription. The accumulated cost is very high indeed, but you are effectively paying a ransom to be able to continue to access the files you create using the software. Local copies of files are fine, but if you can't access the software to open the files, you will be stuck.

Can you download the issues as PDF files?

Is there a Kindle version available, because there is no annual subscription for the device, and the files are added to your perpetual "cloud" storage area?

Marcus

Once you have seated the rivet, if you make the free length of shank protruding beyond the material (the part you will punch to make the head) between 1.25 and 1.5 times the diameter of the shank. That will allow you enough material to form the head. Less than 1.25 x dia is too little to form a complete hemisphere, and more than 1.5 x dia is too much, which results in the bit nearest the plate/sheet being squashed out, like a fungus at the bottom of a mushroom.

The previous advice to use the pre-formed heads on the outside is good, but not always possible.

Pliers-style manual snap tools used to be available from a chap called Dave Noble, but seem not to have been obtainable for some years. There was a good design in MEW or ME some time ago, and I think Model Engineers Laser does the laser cut parts.. The trouble is the operating head is quite large and needs to be able to fit behind the rivet. There is also an air powered tool commonly called a crocodile (or alligator?) which squeezes rivets closed, forming a flat head or a mushroom head, depending on the anvils fitted to the tool. I have one of those tools, but, again, it is usually too large or has too short a throat to fit where I want to rivet.

Marcus

The pinions for this clock are stated as being "best" made out of blued pivot steel. I disagree strongly. Pivot steel/Pinion wire has a poor finish on the surface. Try abrading it lightly with a very fine paper, and you will see the surface is like a ploughed field. The wire will be uncut, so that's not going to provide the low-friction surface you need. Carbide rod or HSS rod would be much better.

Marcus

One of the problems with the dimensions is that while they are all in imperial units, cycloidal gears are usually dimensioned in Module (M), which is a metric measure.

42DP is approximately the same as 0.6M, but not exactly. So if you convert calculations based on 0.6M to imperial units, there is a small error. The same would be true if you did it the other way around, of course.

Using the Thornton's guide to wheel and pinion cutters,

Module (M) = twice the centre distance in millimetres / sum of teeth in wheel and pinion

Or: centre distance = half of sum of teeth x M

= 98 x 0.6 = 59.8 giving a centre distance of 29.9mm

1&5/32 is 29.36875mm and 1&7/32 is 30.95, so you can see that either imperial figure is a compromise and, as the drawing says “approx”.

It is not unusual to vary the depth of cut on a clock wheel, just a little, so I would use a 0.6M cutter, and increase the depth just a touch. That ‘touch’ could probably be calculated from the Thornton’s guide, or perhaps by using Gearotic (which I think now includes cycloidal gears). That thins the teeth slightly, but not enough, in this case, to cause a problem.

I have seen a clockmaker’s depthing “tool” which allowed meshing to take place without disturbing the dividing setup used to cut the teeth of the wheel, so that the correct depth can be judged at that stage. They are not common, and would not be required for this job, although one would be jolly convenient.

It would be worth calculating all the centre distances, as a check, to see if any others need a slight adjustment, or if the errors cancel out as you progress up the train.

Marcus

John Wilding's depthing tool is a simple but useful tool. Plans were included in the BHI Journal around 1979 or 1980, as I recall. It was in the instalments of the first of three clock designs intended to be made on the Unimat 3 (or larger lathe, of course). The clock you are building was also published in instalments in the BHI Journal, as most of John's clocks have been. That's perhaps the source of the reference to the "1st series".

I made that first clock, which was based on a 16th Century one-handed clock, and I made the simple depthing tool as well. The DT design has appeared in several places since then, I believe. And others have published similar designs of DT too.

Marcus

I have the same book, but it shows different dimensions. Are you using an up to date copy? My copy is date d1998.

From the full-size plan, measurements for centre distances (sadly, in old units) starting from the barrel arbor are shown as:

3.25inches, 1&17/32inches (which is the dimension that is troubling you, I think), 1&5/32, 1&3/32, 1&3/32

John Wilding is very helpful and, in my experience, responds to letters. I do not have an up to date address, since he moved, but you might be able to contact him through RiteTime, or the British Horological Institute (of which he is a member. He had an article published in this month's BHI Journal.)

Marcus

Yes; reading what you think you see is a definite hazard.

One method I have met is to read the text backwards. My own version of that is to read it upside down. Bonkers, really; but an interesting exercise, especially when you discover the brain is still able to read what it wants to see instead of what's really there.

Marcus

Good price!

I use 450 x 450 x 16mm which costs £120 (inc VAT) for one piece. Shocking really; but someone else pays for it and I machine it (in fear and trepidation in case I muck it up). It is not supplied through a metal dealer, but a company who take the machined plate and use it as a mould plate, hence the particular size. I suspect the 3rd party being involved in the supply accounts for the substantial markup.

If your supplier is the company I think it might be, I have great trouble getting a firm quote from them, despite my close proximity, so I usually order other aluminium in large sizes from a company in Yorkshire who send it up here at surprisingly low cost. Two way traffic, or what...

Marcus

Could this be a vice? The mechanism reminded me of a vice for thin parts, but if the height of the jaws is adjustable, that would allow it to grip a greater range of thicknesses.

Marcus

I agree with the initial comment on knowing what the part is for, and then selecting an appropriate material. Material selection is about the most important initial step in any job, and in terms of value, a good choice can make a decent job, while a poor choice makes it difficult to get a decent finish, or sufficient strength, etc.

I also agree that grade 6082/HE30 has good machining properties, as does the tooling plate.

I believe the 7000 series grades have better machining characteristics, and are significantly stronger, but at much greater cost. The tooling plate, which I use from time to time, machines nicely, but unless you specifically need guaranteed flat plate, the cost would be hard to justify, as it is very expensive.

So 6082 is the best compromise for the everyday jobs, in my book.

The results depend on speeds and feeds, as with almost any material. Running with a broad cut of 38mm, 0.5mm deep at 500mm/minute is fairly spectacular on a small mill, but although the finish is not bad, machining dry with a carbide cutter designed for aluminium is likely to produce thin hairy slivers which will attempt to weld themselves back onto the job. Running a little slower or less deep gives a finish like chrome plating.

Marcus

I second Brian Hutchings earlier reply re: belt. I have an AUD with the underdrive (motor in the cabinet), and I renewed the belt years ago. Cut it off, then fit a T-belt. The links are easy to assemble, and it can all be done without dismantling anything. Take care when oiling the backgear reservoir. Over-enthusiastic oiling with attendant spillage will shed oil onto the belt and it will slip. Other than that, I have had 20 years out of the current belt, and it looks as good as new.

You might also want to squeeze a rag into the gap at the headstock end of the bed, between the vee and the sheet metal cover at the rear of the headstock. Oil or coolant will run along the bed, and through that gap, then drip down onto the belt. My last rag lasted about 15 years, before I changed it.

Marcus

Harold Hall's articles provided good guidance on how to tackle the job, so they might be your first port of call. As I recall, there have been other similar series in ME over the years.

The book 'Building a vertical steam engine from castings' by Andrew Smith is still available, I think. That deals specifically with the Stuart 10V, and although it was written in 1977, it gives good advice.

I have built a 10V and the only real challenge was in converting the drawings to metric units.

The 10V is an ideal project and leads to a very satisfying model.

Marcus

In practical terms:

I have owned an Oxford welder for more than 40 years, and I can tell you that it will require a heavier-than-domestic wiring feed, and appropriate trips (see Nick_G's post).

In a previous workshop, I began with a 16 amp industrial-style socket wired into its own fuse at the fusebox, but had endless trouble with the earth arrangements, so abandoned that temporarily many years ago. Using the welder via a 13A domestic plug into a good quality 13 amp socket for short welds the socket face plate soon had burn marks on it, and it got very hot if welding over a metre or so at a time. You can't really run more than about 110 amps with this setup. The 2.5mm2 wiring leading to the socket also got hot, which is a potentially serious problem.

So I would caution you not to begin by using a domestic wiring arrangement with this welder, but to install a proper high capacity fuse, thicker wiring and an industrial plug. Domestic wiring is a definite fire hazard.

I also have a large capacity fire extinguisher in the workshop, but that would not be much good if the wiring in the walls overheats.

One other problem is that when the welder is switched on there is a significant surge which can trip a domestically-rated fuse. The more often the fuse trips, the more prone it is to tripping. It's a cycle of despair relieved only by taking note of the differences between types and ratings of breakers (see Nick_G's post).

I'm hoping to add a different type of welder shortly, but it is clear that any welder capable of welding anything other than thin sheet (car body thickness) will draw more current than can safely be delivered via 13 amp domestic fuses and cables. The specs on many models make this clear, and I note that at least one manufacturer will not supply a 13A plug for their more capable welders.

Having said all that, the Oxford is a robust welder capable of heavy duty. I have not had a moment's bother with mine, despite miles of welding.

Marcus

I assume the 'learned discussions' were printed in the journal the month before the article was published...

More seriously;

One difference between a one-pulse-per-rev system and a system which uses one index pulse plus a train of intermediate pulses is that while the 1ppr system calculates the stepper pulse rate needed for the next whole revolution, the multiple ppr system is capable of reducing ongoing and cumulative errors caused by variations between the theoretical pulse train and the actual motion of the work, in each revolution. So it produces a better match between prediction and actuality over the course of a single revolution, in an open loop system. Not quite responding before it happens, but certainly closer to continuous correction.

I agree with the earlier comment about power and electronic motor speed. As far as I can see, the typical variable speed control boards for low powered lathes and mills also use a single pulse per rev and have a visible variation in speed under varying load, especially at low rpm. That is bound to lead to variations in pitch and in cutting performance.

If there is a small range of optimum cutting speeds for a given material and diameter of work, why do we slow down for thread cutting? That seems illogical. I get better results when cutting at closer to theoretical optimum speeds. I suspect the low speed is to allow for operator thinking time, to allow for disengagement of the leadscrew half-nuts. I've had better results using higher speeds but arranging the direction of feed so that rapid disengagement is not required; or by using mechanical auto-disengagement or trip-switch electrical shut-off to cater for the fact that my own internal processing speed is very slow. An automated system, whether CNC or not, copes with this quite nicely. But I would not expect to have to make big compromises on the integrity of the pitch.

Marcus