Help!

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

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

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.

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

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 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

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.