Help!

[Richard ParsonsParticipant @richardparsons61721]

Has anyone any ideas?

I have long been aware that there are more ways than one to ‘skin a cat’. I will not describe my favourite method. Before starting out to undertake any project or part of a project I like to rehears in my mind the way I am going to do it. I do this down to the way I am going to hold the work piece and the cutters I will use. I do this before I assemble the materials I will need and start work.

I want to build Artificer’s Eureka (pub ME 17 Feb 1949). The original clock was a Synchronome with an oscillating balance wheel. The armature formed the cross bar of the oscillating balance wheel. The balance wheel is temperature compensated. No problem except the diameter is 73-74mm and it weighs is just short of ½ Kg . It has to be!, it must contain enough energy to physically turn the ‘going train’.

In a Synchronome time piece, the oscillator receives an impulse every full oscillation. I want to use the Hipp principle where the impulse only occurs when the amplitude of the oscillations falls too low. This means that the electromagnetic armature will not be part of the balance wheel. It will be replaced by a magnet.

The problem is How to make the balance wheel and of what? The classic method is to chuck a piece of steel and trepan narrow groove who’s OD is a little bigger than the width of finished wheel. The groove is filled with brass and flux and the whole lot fused together. The surplus is then machined away etc. The balance wheel finishes at 2 7/8” (73.03mm) diameter groove is 13/16” (20.64mm) deep and about 1/16” wide. How do I machine this? Heating is no problem I have a muffle furnace that will do that, but how do I drain out the flux (borax in this case) displaced by the melting brass.

I have looked at tin cans but these are only 0.010” (0.25mm) thick. I need three times this thickness. There are now two local supermarkets I cannot go into for at least 12 months. I was ‘hodded out of’ by the men from ‘Rent-a-Goon’ for measuring the diameter of any likely tin. You try explaining in your own language to a person who has failed all of their examinations in ‘stupidity’ (well you have to have some ‘nous’ to get a pass). That you did not care what was in the *!??ing tin all you wanted was a flaming tin of the right size. Now try doing that in an impossible language like Hungarian.

My welding is NBG and the local welders will always take the whole thing to bits and weld it up the wrong way round. They just cannot help it – it is genetic I think-.

Any one any ideas how to make the balance wheel? The problem of the spring is yet to come

Edited By Richard Parsons on 08/04/2011 17:23:03

Edited By Richard Parsons on 08/04/2011 17:25:39

[Richard ParsonsParticipant @richardparsons61721]

[Sam StonesParticipant @samstones42903]

Hi Richard,

I feel sure that you will have already perused the ME Forum for ideas!?

If not, then insert `Balance’ into <Keyword> and `Clocks’ in <All Topics>, this brings up several posting about issues I had with balance wheels and balance springs.

In particular, they highlight some of the `struggles’ I’ve had with the escapement of my skeleton clock.

Clearly, the larger size of your intended wheel is likely to introduce additional challenges, which may not have surfaced during the time I was making my balance wheel, c.1973

Suffice it to say that I had five attempts at fusing the brass ring into the steel sink. To get enough heat, and with the help of a friend, I/we resorted to the use of an oxy-acetylene torch.

The primary causes of failure were non-fusion of the brass to the steel, and blow holes in the brass. I put the former cause of failure to insufficient heating and melting, while the blow holes may have been due to trapped flux escaping up through the brass. No doubt the heavier brass was displacing the melted flux (and/or gases). My final attempt (which can be seen in one or two of my pictures) still displays a couple of tiny blow holes. I must also admit to getting wrong, the thickness ratio of brass to steel, and trust that there will still be enough temperature compensation for a reasonable time-keeping result.

As for the spring, that was becoming quite a saga, for me at least. However, thanks to the generosity of one of you gentlemen, I have been sent a spring which has all the makings of a very close approximation to the recommended design.

When I’ve regained some of my health, and the cooler Melbourne weather is upon us, I intend to pursue this to completion. If not, SWAMBO will descend upon yours truly.

 

Good luck,

 

Sam

[Sam StonesParticipant @samstones42903]

Hi again Richard,

Without too much thought, an obtuse idea momentarily traversed some of my neurons.

Since you have actually contemplated using tin cans, could you apply sufficient brass to a flat strip of steel, and then carefully bend the result (with the brass on the outside), to become your wheel rim? After all, the rim will (normally) be in two semicircular pieces.

To remain ductile, I imagine that the brass would need to be annealed progressively as you bend (or roll) the strip to the desired radius.

 

Clearly, there would need to be plenty of brass, and even an excess of steel, for the lathe work to produce the proper article.

 

Sam

Edited By Sam Stones on 09/04/2011 01:28:53

[Richard ParsonsParticipant @richardparsons61721]

Why tin cans you ask. They are good steel and circular. My first idea was to Locktite and rivet the brass shim on to the tin then make up a boss weighing some 300 grams. The problem here is the thickness (or rather the thinness) of the metal used. The ratio of thickness of brass to steel shown by artificer is Brass 0.08” (2.03mm) to steel 0.05” (1.27mm). At the moment I am looking at Aluminium as a possibility as I have some.

Hi Sam you have been there done it, and got the ‘Tee’ shirt. What flux did you use and what brass? There is a very good site on brazing here. Here they stress the need for flux displacement/escape. I know from the past, there is a need to use a flux which assists in the ‘out-gassing’ of the melted metal. My muffle furnace is quite able to melt enamels and silver, so brass is no problem. I have even made ‘Sheffield Plate’ in it. It just takes time. In his book Watch and Clock making and repairing W.J Gazeley shows a process he calls ‘hammering down’ to compact the brass after melting and initial machining.

[Richard ParsonsParticipant @richardparsons61721]

I have tried the link again here. This PDF is realy worth reading as it applies to all forms of brazing, silver soldering and even soft soldering.

Edited By Richard Parsons on 09/04/2011 12:50:31

[Richard ParsonsParticipant @richardparsons61721]

Graham The reason I think that Artificer changed his mind about silver soldering and talked about soft solder is the problem of the distortion of thin brass at silver soldering temperatures even in a furnace. From past experience it all ends up as old Curley put it ‘like the waves of the Danube’.

I have a set of slip rolls and tried the idea of rolling circles, but they are difficult to make them a true circle. It was then I started measuring tins. Most of them seem to be within a few 0.02mm of a true circle. And if you leave an end in it will stand a lot of ‘rudery’ until they distort. Once you have made up the rest of the wheel and attached it you can then cut out the end with a tin opener.

The temperature compensation depends on average movements of the various parts of the wheel. I am at the moment working on making a ‘foliot’ using Harrisons grid iron compensation system. After all the bulk of the mass. in Eureka, was along one diameter.

[Sam StonesParticipant @samstones42903]

Hi Richard,

I have to return my `T’ shirt, because it’s too long ago to remember anything about the flux, and I can only guess at what (grade of) metals I used. I think the steel was high carbon (probably silver steel), and the brass was `off-the-shelf bar from the local supplier. I/we took no measures to release the flux/gases. When I say `we’, I made the parts in my own workshop, and then took them into work where they had the oxy torch.

I recall making the brass ring a tight fit onto the (interface) diameter of the steel `sink’ and, before fluxing, I made absolutely sure that everything was clean. An old RAF trade-training catch phrase was `Clean and Tin’. But that was for soft soldering electrical work.

Upon scanning the 1972 ME (five part) article, it would appear that I actually deviated from John Stevens design of a one-piece brass wheel, and followed the bi-metallic design as described by Gazeley. What was I thinking???

I have no real experience of rolling except from forming some 1/16″ aluminium sheet into large cylinders about 8″ diameter and 5″ long. They were casings for the lights of some TV show or other. Again too long ago. However, with respect to its visibility, unless you obtain a truly round wheel, it will look somewhat primitive as it oscillates. That has been one of the issues I’ve had to address wrt the helical balance spring in my clock. In other words, unless the wire of the spring is accurate in pitch, diameter, and held central at both ends it will `wobble’ and look odd.

I think you have started at the right `end’ of the clock, because once you have determined the `beat’, then the gear(box) design should be relatively simple.

Good luck,

Sam

[Richard ParsonsParticipant @richardparsons61721]

Sam Thank you. You might well have hit the nail on the head. It does not matter what the thing looks like, what is important is the regularity of the beat. I can monkey with the ratchet and going train later.

I was thinking about a bar oscillator (a foliot) using a Harrison grid iron arrangement. This evening I remembered a ‘thought exercise’ I did some years ago as how to ‘improve’ on the ‘grid iron’. I invented (others have probably done the same) a different type of compensation. Instead of using the 5, 7 or 9 bars Harrison used I used two tubes and one bar fitting them together concentrically. I can calculate the natural oscillation of a foliot for a given length. Once I have worked the logic of the expansion I will get EXCEL to work out the lengths for me.

Actually the one clock seems to have come up for sale and the sellers published the whole of Artificer’s writings on the matter. The weight of the original balance arms comes out to approx 25% of the total weight, this supprised me I thought it would be less.

I do not know if you has a shufti at the second link I gave about brazing. There is something in it that may give the Boiler Builders food for thought.

Cheers Dick

Edited By Richard Parsons on 10/04/2011 05:09:52

[Richard ParsonsParticipant @richardparsons61721]

Graham – Mine are the pyramid type! And tend to make spirals rather than circles. But they are better than nowt and they ‘do’ for the Hungarians most of whom do not know if ‘it’ was drilled, punched or counter bored.

Yes I like clocks they can be open to interpretation. This one the Eurka uses little metal which is very scarce over here. Two or three years ago Worthy Oriental Gentlemen appeared with suitcases full of money and the country was swept clean.
Thanks

Dick

[BusterParticipant @buster]

I made a two part balance years ago and found it very easy but i did leave enough room between the parts for the solder to flow and the parts were over sized for trimming later, cheers David

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