Member postings for Sam Stones

Hello again, especially Dick, Ian, and Norman,

Thank you for all your ideas, I really appreciate getting your type of assistance.

Just a couple of points about the use of guitar strings, and also in making extra equipment. At the risk of repeating my earlier comments, my target is to finish the clock while I still have some dexterity left. I also consider my workshop to be a very temporary affair, and am reminded on occasions that the Hobbymat lathe is, after all, still on loan.

As some of my pictures show, the mechanism of a skeleton clock is intended to be fully visible. That’s the primary purpose of piercing the frames and wheels. In the case of John Stevens clock, the most obvious animation is the balance wheel and spring sitting inside the top `cage’. The nice thing about steel guitar strings, is that they are already polished. So if I can keep them in that condition, there will be less effort needed to bring them up to scratch. I would agree however, for those who like that sort of thing, that the spring could be a nice blue colour after tempering, but once again . . .

I like Ian’s idea of passing a low voltage current through the wire to soften it. I did notice that being rather fine, the wire burns immediately (like wire wool) if placed in a naked flame. I could also imagine that with care, the use of electrical current in this way, could be employed in both the rehardening and tempering after the wire has been wound to size. Holding it to shape would be quite a challenge however.

In my next comment, if not before, there is likely to be an element of `egg-sucking’ for grandmas. However, I’m inclined to believe that winding the wire around a 4mm diameter mandrel to get a finished diameter of about 8mm, does actually subject a percentage of the steel section to stresses above the elastic limit. How much of this will be in tension (or compression), I could not imagine. Clearly, there would also be a certain % of the section which does not get stressed beyond the yield point, or the spring would come off a 4mm mandrel at 4mm without any `snap-back'.

Machinery’s Handbook offers a table for Arbor Diameters for Springs Made from Music Wire and although it doesn’t actually mention the OD I needed, by extrapolation and my own tests, I seem to be on the right track at 4mm.

In terms of `annealing’ (I have difficulty with the definition of annealing), early tests of heating previously wound coils to about 200 deg C showed very little relaxation, and all the wire that I have wound since remains very close to what I wanted without this treatment.

Finally, and switching to Norman’s comments about the case (thank you Norman), and where to buy them, I have elected to follow John Parslow’s approach. Refer ME p202 15 August 2008. It concludes John’s article called "15-day skeleton timepiece".

With the help of a friend with some good woodworking machinery, I now have a pine base suitably stepped, together with some pieces of Tasmanian oak beading to trim the surround. The ends of the beading have been mitred which is a task I have never enjoyed via the hand-sawing method.

I’m currently waiting for some shellac to dissolve and before I glue I will begin to apply this to the oak in multiple coats alternating with a rub-down with fine sand paper. I trust that PVA will hold everything together. The centre area of the base (inside the glass) will be covered in a dark blue material, the sort of cloth that is turned into tracksuits and the like. There’s a glass supplier down the road who has made fish tanks and display cases, so I’ll be talking to him next week. Alternatively, I’ll get him to cut the five pieces of glass, and glue them in place with clear silicone. Depending upon how the silicone runs between the glass, I imagine knifing off the excess to leave a very clean joint.

I reckon the French polish will be ready by now.

Regards to all,

Sam

Thanks for your comments Michael.

I agree with you about fluidics, and how it doesn’t seem to have established a place in technology. For companies into pneumatics, it was probably attractive in the early days, but I would assume that there are many more electronic switching solutions rather than adopting this method. I've seen (on TV) the results of using air lines to trigger lightening strikes through copper wire, but I imagine even this would not need sophisticated fluidics.

Regards,

Sam

When I introduced the thread about near empty tubes of super glue, and although it was a significant irritation at being ripped off, I was actually in the middle of some final experiments to make a usable balance spring for my skeleton clock.

In previous threads about balance springs, I searched and tested several ideas to try to find (with my limited equipment), a reliable method. As my own notes show, I had determined that a wire diameter of 0.2mm (0.008") would replace the flat section as used in the original clock design. This has since proved to be fairly accurate since the clock is now beating with an accuracy of less than 1 sec/hour, and responds well to fine adjustments.

That said, I can briefly describe my approach to making my balance springs. The most significant problem I have had when winding the spring onto a 4.0mm diameter mandrel has been how to uncoil it successfully after winding. Once released, the usual result has been for the spring to fly open and to wrap itself into an unuseable mess. There have been some very useful comments posted, some of which pointed to additional twisting which takes place (unseen) during the winding process.

Michael Williams wrote :- The traditional method of making very small springs with limited equipment is to pass the feed wire through a hole in a piece of flat soft wood and arrange for the flat part of the wood to bear down on the coils that you have already made . Until such time as you deliberately remove the wood the coil remains tight and under total control . You cut off surplus feed wire with the wood still in place and then slowly lift it away . As an added bonus there is an element of screw-cutting going on in the wood and after a few turns; a neat set of grooves form which help to keep the winding pitch constant . Please be very careful when winding springs under power - it is a terribly dangerous process.

Perhaps it was the hidden twist and how I anchored both ends of the wire which were responsible.

To avoid weakening the mandrel I had drilled the 1mm anchor hole through the larger 1/4" diameter section. What seemed to be happening was that the wire was skidding down the side of the step, thus introducing extra twist. This was rectified in my final attempts.

The free end was weighted and the wire was passed over a simple pulley. I took the trouble to stop the weight from spinning, expecting that any back and forth twisting would be transferred to the spring. Taking note of all the warnings, winding the wire onto the mandrel had always been done by hand with the main power switch turned off. This was very tedious and tiring for my old hands and fingers, since reaching the three-jaw was awkward. I had also chosen to wind the spring ACW so that I could see a little more of what was happening to the winding process.

It was at that point that I decided to wind the wire under power with the lowest lathe speed (267 rpm), and in reverse. The chuck was bolted so there was never any danger from it unscrewing. I also calculated that I had at least 15 seconds before I had wound all of the 1 metre length of guitar string onto the mandrel. I stood ready to switch off, and hey presto, a nicely wound spring. That was until I removed the wood which Michael had suggested.

Another tangled mess!

That was when I went off at a tangent, and began to explore the possibility of gluing the wire to the mandrel, and using a solvent to let the spring slowly uncoil. The traditional `glue’ in clock making is shellac which dissolves in methylated sprits. This would be ideal, or so I thought. So I tried again giving the tightly wound wire a good coating of shellac, waiting overnight for it to set.

It didn’t work so I figured that the shellac had not found its way under the wire and onto the mandrel. With that fixed, I tried again. The wire instantly flew into another mess, and another guitar string went into the bin. I interpreted this result to mean that the shellac was too brittle, and/or hadn’t bonded sufficiently. It was also possible that the meths had not fully evaporated completely from under the coils.

That’s where the super glue came into the picture. I should (again) point out that super glue (cyanoacrylate) sets by combining with moisture from the atmosphere or from your breath. It is also supposed to soften in acetone, which would be ideal, or so I thought. With a very thin coating of super glue applied to the surface of the mandrel, I tried once more, applying two coats to the tightly wound coils. Several hours later, I cut the wire.

When I fished the spring from the acetone, it became clear that although the glue had turned white(ish) it was still present. Very carefully, I teased the coils free, and found that I had to strip off whiskery lengths of glue still attached to the wire.

Remember, the diameter of the wire is only 0.008".

This posting may provide food for thought, but it has become more of a saga, so I must end here.

One question. Why didn’t the glue dissolve in the nail-polish remover?

Gentlemen,

In response to a couple of questions about my de-burring technique, especially from Pekka, I cobbled together a couple of schematics from what I remember. It was, after all about 30 years ago.

Michael Williams has reminded me also about the fluidics phenomenon, which I seem to recall involved Enots. However, I hadn’t realised that the valves mentioned could cope with liquids besides air.

This posting could be titled - How I de-burred the tiny holes in the PMM valve bodies.

Just to back-track a moment, the inside bore of the PMM valves had a honed and highly polished finish. That was eventually my minimum standard. Where the five 1.0mm holes broke through however, the best result was a sharp corner, while the worst was a burr. Clearly, the PTFE spool would be damaged if this condition prevailed.

The solution was quite a simple idea really, and one which Pekka alluded to in his earlier posting above.

I settled on tripoli as the preferred powder, and I presumed it was the same stuff found in liquid metal polish. It was cheap and could be mixed with water, so the PMM was safe from solvents. I added a very small amount of wetting agent to help to disperse the powder in the water, while avoiding a severe dose of the froths.

The mechanism was fairly simple too. I had an old washing machine motor and added a large ball race to the shaft with about 5mm eccentricity. This eccentricity was to produce my up and down movement. A couple of polypropylene (PP) adaptors suitably spigoted to locate into the bore of the valve body closed off the bore, one of which was drilled through to allow the slurry to pass. A simple ball valve sitting inside the bottom adaptor ensured a reasonable one-way flow of slurry. A stubby length of RPVC about 40mm diameter formed the body of the contraption, while providing a miniature priming tank for containing the slurry.

The tricky bit was still to come, ie. how to make the pumping action take place without too much leakage?

As I recall, this came in the form of a couple of rather chunky `O’ rings roughly the same diameter as the RPVC tube and about 6mm in cross section. Besides helping to form a seal between the tank and the outside world, there was sufficient `give’ in the `O’ rings and the rest of the contraption for the eccentric ball race to generate a pumping action. In other words, to squash the assembly up and down, forcing the slurry through the tiny holes.

Fifteen minutes of this while I carried on with something else, and the job was done.

It took a low power microscope to view the beautiful radii which had replaced the burrs and sharp edges on these largely inaccessible places. Although I’ve searched amongst my old samples to provide a picture, it would appear that they have all been dumped during successive moves.

Regards,

Sam

Gentlemen,

Thank you for your compliments, I’m only pleased to have somewhere to divulge some of my `tricks’.

Before I disclose my method of de-burring the 1.0mm holes into the body of the PMM (Perspex) valves, I need to make a couple of comments about the more recent postings.

I fully agree with Pekka regarding the machining and use of unfilled PTFE (Teflon). However, once its basic properties like creep, coefficient of friction, and inertness are understood, these can be dealt with as required.

Pekka, your comments have aroused my curiosity. I suspect that you have worked in a research environment where these valves (or similar) were in use. I designed them specifically for one task in a biological research laboratory. From your other comments, I have to say that I also developed and made several other pieces of laboratory equipment, none the least being an infusion pump which would physically accept standard syringes from 5ml to 50 ml.

Stepper motors were indeed used as the motive force, while the engagement and re-setting of the pump and syringe was achieved using a gearing-down lead-screw system not unlike a lathe split-nut arrangement. As I recall, with a wide range of speeds and syringes, discharge amounts could range from a millilitre or two over several hours, through to a relatively quick discharge of 50ml in just a few minutes.

Another very serious semi-production task I developed, also involved machining elastomers. This was where the kitchen freezer became an import part of the equipment. It was of course, necessary to push the frozen food to one side, to make room for the items to be `frozen’.

Coping with the high `discharge’ rate of the polyurethane swarf was perhaps the hardest part of this production line, until my son and I decided to let the swarf wrap itself around the wheels and remove it later. A sharp Stanley knife worked wonders.

As for the PTFE spools, and to pick up on the comments from Pat, Hansrudolf, and Andrew. Using the 1ml syringes as the `power’ source as mentioned before, the spool was caused to slide a mere 2mm, so that either one of two fluids could be switched rapidly as they were directed into the specimen bath. A material combination with minimal stick-friction was required. The best materials I had access to, and which were suitable for my modest home workshop were polymethyl methacrylate (PMM - better known as Perspex), and polytetrafluoroethylene (PTFE - better known as Teflon). Together, and with the degree of fit I had determined as suitable, these two materials produced virtually no stick friction, and provided a positive seal between the adjacent fluid channels.

Since you asked Hansrudolf, all of my work in making these valves was carried out on my Myford ML7, and a nerve-wracking Chinese mill/drill. It wasn’t (and dare I suggest still isn’t), possible to use a micrometer to measure the central diameter of the spools to the level of accuracy I found necessary, especially since this middle section (web) of the spool was only 1.5mm wide.

At this scale, PTFE is too soft and slippery to get any kind of sensible reading. What I did was to use Go/NoGo gauging and selective assembly. For repeatability, the Myford was good enough for me to leave the cross-slide locked, and make final surfacing cuts without disturbing anything but the saddle.

Getting back to the original Thread, and why de-burring was so important. The minimal interference fit of the central section of the spool and the valve body, was still such as to cause the PTFE to (dare I say) exude into the 1mm port holes. Therefore, any kind of sharp edge was likely to interfere with, and even shear off, a tiny sliver of PTFE from the spool. Since some of the research involved measured millivolts, any liquid bridging the central spool web was likely to interfere with these low voltage measurements.

This posting has growed like Topsy, so I’ll add another posting to describe how I de-burred the holes.

Regards to all,

Sam

To obtain a positive seal between the inside of the PMM and the PTFE spool, while bearing in mind that PTFE does creep, I made the centre section of the PTFE spools a small amount larger in diameter, ie. about 0.008mm (0.0003"). This was all I was prepared to trust from my lathe in a semi-production sense. The unfilled PTFE was ideal in terms of its low friction characteristics, especially that of `stick’ friction. Both materials (PTFE and PMM) had to be relatively inert to the fluids being processed.

In response to PekkaNF’s comments about machining PTFE, it's a material which is not easy to grip. Unlike POM (polyacetal, Delrin,) which is more rigid, and swarf normally comes away cleanly (unless static builds up and pulls the swarf onto the workpiece), unfilled PTFE is soft and slippery. Its creep resistance is very low too, so it becomes necessary to surround the workpiece with metal as a means of reducing movement (creep). At the time, I had quick release collets, so gripping the PTFE bar-stock was not an issue.

Another aspect which came to my notice in terms of the performance of the valve, was that at 19 degrees C, PTFE goes through a phase change and sharply increases in volume. This had to be taken into consideration for valves specified for use in applications where the operating temperatures were above 0 degs C, but below 19 degs C.

For these special lower temperature versions, I made the diameter of the PTFE spools a small amount larger to accommodate this drop in volume. I also had to supply special instructions for when the valve was not in use. Researchers could either keep the valves in the fridge or strip them down to remove the spool. Storing the separate parts at room temperature was not a problem, although an important part of preparation for use was to reduce their temperature to below 19 degrees, and to keep them below 19C while in use.

Returning to de-burring, I think Weldsol’s comments about using a sacrificial bar has merit, although I needed to make quite a few of these valves, so it would be necessary to jig the bar to accurately locate the hole centres and avoid significant (bar) wastage. This wouldn’t have been too much of an issue since I was already drilling the holes with a drilling jig. However, I do wonder about what would happen if the drill wandered slightly.

It doesn't want to let go! 

Regards to all,

Some considerable time ago, and quite by chance, I found myself designing and making a miniature five-ported hydraulic valve for use in medical research.

It was machined from solid Perspex (PMM) and measured about 26mm long by 22mm wide by 16mm deep. It was to be secured to a microscope stage operating at fairly high magnification, and hence had to be remotely controlled to avoid generating vibration. I chose to make the spool from Teflon (PTFE), which had to seal completely, two fluids being switched by the valve as the fluids passed through it. In other words, there must be no leakage.

The main bore of about 9mm diameter had to be machined and reamed with the minimal amount of frictional heat, so that final lapping (essential for accuracy and finish), didn’t cause crazing. Some liquids can be seen to induce stress-cracking from inbuilt stress, (a bit like happens when a high density polyethylene injection moulding comes into contact with detergent solutions). This crazing of the PMM was initially found to be a significant setback, until I developed a satisfactory low heat machining solution.

Once the word got out, I finished up making and selling several dozen of these individually manufactured valves to various research groups around the world.

My question is :-

To answer Nobby’s question, there are several 12BA screws in my skeleton clock. They hold the hardened end (thrust) plates in position for the bottom bearing of the balance wheel arbor, and the bottom bearings of the two escapement arbors.

Having said that, and this is about tapping and the use of tap wrenches, I have to admit that under these circumstances, I twirled the taps in and out between my finger and thumb.

AND, I was only tapping into brass.

It’s nearly forty years ago so I can’t remember exactly, but I may have assessed the resisting torque versus the tap’s strength together with the squeak coming from the brass/tap, to know when to back off.

If we are talking about screw size, my ego is quickly deflated when I peer inside an old watch.

Regards,

Sam

Hello Dick,

The delicacy of making the balance spring in my clock is such that I would find using a hot melt adhesive a bit too risky, but thanks for the thought.

Great stuff this Super Glue (cyanoacrylate), but is it just me or do others get ripped off when buying it.

The regular, off-the-shelf tubes of glue are marked NET 3g (three grams), but how coarse is the NET? Time and again when I buy a tube of this stuff, the tube certainly does not contain 3 grams of liquid. OK, so with a density of 1.1 g/cm3, the tube would contain less than 3 cubic centimetres.

But take a look at the photograph which compares a full tube with one which I squeezed until the air was expelled. Admittedly, I was in the middle of a job and couldn’t stop before using about two drops prior to re-capping the tube. I also have to accept that some of the glue is lost in filling the nozzle, but what happened to the rest?

Super glue was once about $2000 (or more) per litre, but the price of a tube (in a pack of eight) at the local cheap shop this morning was 25 cents per tube. Each tube weighed the same, and the glue could be heard sloshing about when shaken (not stirred). However, since there was only about 0.5cm3 in a tube, the retail price still comes out at about $500 per litre.

Hi Stephen, Dick, and Norman,

Thanks for your comments about using ball races, and about handling the main spring.

Given more time and a proper workshop, I would be very tempted to fit ball races into the clock. If you know of Rex Swensen (Sydney, Australia), he is a strong advocate of fitting them into clocks, and has offered several important engineering ideas to support his work. His notes can be seen in another forum.

As for removing the main spring, I can only offer the following comments.

Your word `gripe’ Dick, certainly describes the brief whirling sound the spring makes, as it unblocks itself. I had thought that this would have been fixed with oil!?

When I bought it from Messrs E E Gray of Clerkenwell, a London supplier back in the 70's, I simply inserted it (halfway) into the barrel before cutting it free from the wire binding. That’s where it has been ever since, and has never been unwound. At this point in time, I would not be able to tackle the exercise of removing it alone. Perhaps I should take it to a clock maker who should have a spring winder?

As a general warning to anyone who doesn’t know, there is still a lot of `power’ left in a spring of this kind. I understand that some of this power is often produced by the spring being initially manufactured with a partial curve in the opposite direction to the way it is eventually coiled in use.

I’m also left wondering what lubricant would best suit this situation, and for long term use. I know of lubricants containing a suspension of micro-fine PTFE (Teflon) particles.

Would this be a better bet?

Thanks again,

Sam

The new pictures show the three essential elements which are a part of the skeleton clock `coming alive’.

The fusee and barrel can be seen connected together via an 80lb (36kg) breaking strength braided fishing line. It was a nice stroke of luck that the line was yellow. It seems to go well with the brass.

During winding, the line is transferred (upwards) from the barrel to the fusee at a decreasing rate, thus providing a type of torque compensation as the main spring approaches being fully wound. I’m not convinced that the profile of the fusee, generated by a 2" radius, accurately compensates for the increasing main-spring torque. But it’s going to have to do, cos I won’t be making another. However, while I was winding it up completely for the first time, I could feel the compensation taking place.

Also visible in this picture, although not easy to determine, is the stop-work mechanism designed to prevent over winding, and thus avoiding having the line drop off the end of the fusee. It is identified by the notched steel arm pointing away from the camera. As the line is wound onto the fusee and travels towards the front of the clock, the spring-loaded steel arm is deflected into alignment with the snail-shaped hook, just visible under the small end of the fusee.

Although concealed within the `great wheel’, there is a blued-steel circlip-shaped spring called the maintaining spring. This provides continuing power to the clock during winding. While it is not obvious, there are 29 items (including screws) which make up the entire fusee mechanism.

The next picture shows each of the important parts of the escapement.

I deliberately chose a long exposure time to display the movement of the escapement. Hence the reason for the blurred image. There are already pictures in this album showing this part of the clock before the clock came to life. The oscillation of the lever is just visible as a double image above the fifteen-toothed ‘scape wheel. At the top of the picture is the over-stiff spring, responsible for the fast beat. It is made from 0.011" (0.28mm) diameter wire, whereas my calculations suggest it should be 0.008" (0.2mm) diameter. Other calculations reveal that this thicker wire produces a spring which is approximately twice as stiff as it should be.

My last picture to be added shows the bell and hammer in place. This `once-on-the-hour’ strike is just about to take place in the picture. However, because the clock is running at more than twice the correct speed, it currently strikes every 28 minutes. The hammer is lifted via a pin on the `minute’ wheel and `lifting piece’ positioned at the front of the clock. It was necessary to introduce a spring which would stop the hammer from bouncing more than once on the bell. This seems to work OK.

The rough-looking screw just about the hammer head provides end adjustment for the `fourth’ wheel (contrate), who’s teeth are turn at right angles to engage with the 14 toothed escapement wheel pinion.

In my opinion, that sort of finish is typical of very low grade mild steel (MS), where the swarf is tearing and periodically reattaching itself to the workpiece.

Someone gave me some old lift (elevator) 3" diameter winding axles, removed from a city office block in Melbourne. I was delighted until I came to use it. It turned out to be rubbish, and wouldn’t turn or mill without wearing out cutters.

With reference to this thread, a test with the same cutters on some free-cutting MS might prove me wrong. And of course, having the cutter height set correctly if that wasn’t already checked.