Mild Steel as material for gears

Edited By Mogens Kilde on 12/12/2010 19:09:09

 Correct, i forgotten the cast iron in larger gear wheel ... same material running togheter are a bad idea due wearing properties.

Hello Morgens   there are two books which whilst they were written at the middle of the last centenary are still well worth looking at. The books are both by F.W. Britten. The most useful is ‘Watch and Clockmakers’ Handbook (Dictionary and Guide). This is a sort of encyclopaedia. The other is ‘Horological Hints and Helps’. I think I bought my copies (which are reprints) from Camden Miniature Steam Services (usual disclaimer). They advertise in the Model Engineer.

What you want to do by shortening your clock will mean a complete redesign of the whole clock. There are very close relationships between the length of the pendulum, the count (number of teeth) of the ‘scape wheel, the span of the escapement and the ratios in the ‘going train’ (the rest of the cogs). It is the pendulum length which is the foundation of the whole clock. To put it more simply a clock is a device which counts oscillations. Change one part and you will have to change all.

If I may give you one more Krona’s worth of advice do not work to normal engineering ‘fits’ they will be far too tights. Clocks are built with a rattling good fit. I learned this the hard way. It took me many days to figure it out. Keep everything LIGHT! (as light as you can).

NJH - thanks for the ‘plug’. I have used the method I describe in Model Engineer and with care, it works well.  I have used it to make the wheels for three clocks so far. It can be used to make straight spokes for flywheels and other similar things. I now know how to use it to make tapered spokes, but there are complications. Until I have used it and know it works I will not write it up. If anyone has problems with the method, send me a message via this site.  I must also thank the Editor of Model Engineer for the drawings (mine were dreadful).

I will not comment on steel/cast iron wheels, I have never used them.

Edited By Richard Parsons on 13/12/2010 06:35:36

Edited By Jens Eirik Skogstad on 16/12/2010 19:12:12

Mogens   Hi there again.  I must have been half asleep or had too much palinka (a sort of Hungarian rotgut or Snaps to keep out the cold) when I wrote to you not knowing about the use of iron.  Have a look at this clock - Sorry you will have to Google for it Salisbury Cathedral clock because some of the hypertext link throws up X""$£%&***! smilies.  It has been running since 1386. The metal is certainly wrought iron (hammered not cast iron). Like the headsman’s axe at the Tower of London it has probably had a new handle and perhaps a new head but it is a real old genuine axe.

There is a modern reproduction again probably in mild steel here. The point about both of these clocks is that they are very large and are very poor timekeepers.  You should also note that they use ‘Lantern wheels’ not pinions. Unlike Harrison’s lantern wheels in his chronometers where the bars rotated in brass disks these do not rotate. From the look of the reproduction of Wallingford’s clock the gears are involutes and in the Salisbury they were ‘filed up to fit’

Edited By Richard Parsons on 17/12/2010 16:13:21

Edited By Richard Parsons on 17/12/2010 16:20:39

Yes the Salisbury clock was the Rolex of its day. Of course it was used to trigger the bell or ‘Clocher’ which summoned the inmates to do their services (matins, vespers complin etc). The clock was looked after by brothers called ‘Vergers’ who used sundials to help them reset the machine. The point about the machine was that it would run and give them the time during overcast weather, at night and could ring bells.

The real quantum leap was the use of both the Verge escapement for marking the passage of time and the ’fan’ used to control striking mechanism. Richard of Wallingford’s verge is a real ‘dainty’. In many ways it was easier to build than the pallet verges with their large ‘scape wheel. 

Has anyone ever measured the accuracy with which the Salisbury Clock was built? The ‘clock wrights’ had no standards to work with. You could not go out and buy a 6 “ ruler. No machine tools (much) just forges, hammers, etc. The instruments they had were dividers, trammels, scribes and straight edges. How did they make the straight edges? 

Somewhere in Salisbury there are the Master Mason’s marks which were the reference point for the Stone masons to work from.  These determined the size of the whole building and each part of it.