Dark Lady Clock

Don't worry John. When this style of clock was first made do you think they had half the precision you have achieved and yet they still ran. At worst it will perhaps need a slightly bigger rock to power it. You would not have to make new wheels just run a slitting saw or straight flycutter through the gaps. The top curve is to avoid having a sharp corner caused by a flat top as the real work is done by the flank.

Thank you, Bazyle ... That's very succinct

MichaelG.

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[John Silver] : Could you please post a picture [flatbed scan would probably suffice] of the teeth on your wheel; and of the flycutter that you have made ? ... It may be that a 'second operation' using the flycutter is all you need & it would be useful to compare the actual profiles.

Edited By Michael Gilligan on 25/07/2016 07:02:08

I used the single point cutter from the drawings, not a precision tool but it cuts regular teeth, if of questionable profile. A light touch here and there with a fine file helped free up the running. They are very forgiving, which I suppose is a feature of this clock.

John If you consider what tools were available in the early days of clock making The wheels and pinions would have been cut by hand probably using home made saws and files your clock should run Don't make the pivot holes too tight To be pedantic you don't cut the teeth, you cut the space between them

Roy  ps I find the steady slow beat of this clock to be very  therapeutic

Edited By roy entwistle on 25/07/2016 08:54:38

Somewhere I once found or was directed to a paper that demonstrated convincingly that the only reason cycloidal gears are used in clocks was tradition. For low friction, efficiency and tolerance of mis-alignment involute gears were shown to be superior. But they need more cutters.

The antikythera mechanism had dozens of gears with hand-made 'square' teeth...

I note you say your bushes are a close fit, every thing I have read about clock making suggests the bushings need to be loose enough that the gears will slide freely from side to side if the frame is tipped. If the clock is 'stiff' consider opening out the bushes a little before condemning your gears.

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Start here, Neil, and follow your nose

http://www.csparks.com/watchmaking/

Lantern Pinions present a special case though.

MichaelG.

Now that's a mechanism I would ultimately like to build - Antikythera - probably the most amazing piece of engineering ever built. I have ever found any plans, although the curator of some museum built a pretty accurate version, and even demonstrated how the Greeks made the gears (look for the Horizon program).

I'd love to get more info on the Antikythera mechanism (I don't want to build the lego version though )

Anyway,I took this video of my main gear and the second wheel pinion - it was fairly critical setting the spacing between the gears but it does seem to run freely??

Edited By John silver on 25/07/2016 08:58:25

Edited By John silver on 25/07/2016 09:00:50

They are not unlike the wheels in the windmill at the end of the road, though on a smaller scale.
New wooden teeth on the mill are roughed out then allowed to 'bed in', they soon take up an eficient profile and quieten down.

As you say, the original would likely be made in a smithy or by a mill wright so the techniques and tools at our disposal make it much easier.

I have been asked to make a scaled up version in timber for a garden.

That looks pretty good, John Silver

Sorry if I pressed the Panic Button last night.

MichaelG.

Edited By Michael Gilligan on 25/07/2016 09:01:14

No problem, although I'm I still think I'll need to re-do at least one of the lantern pinions with a straighter drill entry

I guess the proof of the pudding will be when I have fitted the second (& third) arbors and then see who they all turn and whether they jam up or not??

Right website although I couldn't find the route again it helped me find the page via google:

**LINK**

Neil

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1. http://www.csparks.com/watchmaking/
2. http://www.csparks.com/watchmaking/CycloidalGears/index.jxl
3. http://www.csparks.com/watchmaking/CycloidalGears/RichardThoen.xhtml

Admittedly that final link is buried in the text ...

" Finally, I would like to mention a privately published monograph by my gear-expert friend, Richard Thoen. This work explains why, in his opinion, cycloidal gearing belongs entirely in the dust-bin of history."

... but I thought you might like to follow the plot.

MichaelG.

Ah! I have read hat page a few years ago so I didn't want to re-read it all, I just looked at the obvious links

Neil

He quotes this on those pages

it wasn't until the mid-20's -- when Professor Earle Buckingham invented the involute function

My father reckoned that this view cropped up during WW II. When we were on holiday in my very early teens we saw a type of small crane on a docks that clearly used involute gearing with 18xx cast into the gears.

As I understand it the original source is mentioned here

**LINK**

The earliest "engineering" reference to them I have ever found dated back to the very late 1700's.

Back on topic.

Ball races are sometimes used on mechanical precision clocks. This seems to indicate that the traditional mystic certain degree of looseness isn't such a good idea either.There is a web page some where showing the reduction in friction ball races can give. Sorry but I didn't keep a link.

John

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Interesting point, John

I'm sure that Euler deserves credit, but equally unsure that he invented the mathematical function [which is what Earle Buckingham gets the credit for].

Here is another interesting page:

http://www.metalmite.com/2012/11/who-invented-the-involute-gear-and-metalmite/

[which may, or may not, be a demonstration of a 'factoid' being created]

... Note the credit at the foot of the page.

MichaelG.

I don't think that the mathematical function is much use. Just like cycloids the profile needs modifications in order to be of any use - undercutting being a problem with involute.

Anyway here is a different account of gear teeth.

**LINK**

Also

**LINK**

My interest has always been more just how did they do it in the past on all sorts of "things". I doubt if it was this way in the case of gear teeth.

**LINK**

John

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Edited By Ajohnw on 28/07/2016 20:31:30

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On the contrary ... I suspect that it was the discovery of a mathematical function that permitted mass-production.

Euler knew the geometrical description, but that only enables a limited range of production processes.

Beyond that, I'm out of my depth ... So please don't expect a meaningful debate.

MichaelG.

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Edit: p61 of this book seems to support my opinion:

https://books.google.co.uk/books?id=TrbHcs-cSFAC&pg=PA61&lpg=PA61&dq=euler+involute+gear&source=bl&ots=kOlHDiz64N&sig=WXaVlRI3KBtEAmVRc-TAIKKJI9k&hl=en&sa=X&ved=0ahUKEwixoLjx4pbOAhXKAMAKHW_dAFMQ6AEIKjAG#v=onepage&q=euler%20involute%20gear&f=false

Edited By Michael Gilligan on 28/07/2016 22:08:54

One link I posted suggests that involute was in wide spread use in the 1800's.

What got me going on this subject before, a long time ago was a comment that only cycloid was used in the UK around WWII which is clearly a load of rubbish. Maybe this was true of some instrumentation areas but clearly not in others.

John

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OK so I'm on to planting the train and have sized up the second arbor and the main wheel and second wheel run nice and smooth.

However, it's a bit vague on the actual position of the main wheel on it's arbor. The text says "Position the main wheel collet 8mm from the rear of it's arbor and secure with loctite"

By collet I am referring to the spacer without the securing screw..

Looking at the photo's, the main collet appears almost flush with the main plate. I would assume you want clearance to stop the collet rubbing??

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Yes ... It only needs a few thou' but you definitely need clearance.

A good 'rule of thumb' is that when assembled, you should be able to hear a 'click' from each arbor if you turn the clock over ... front down to back down [or vice versa].

MichaelG.