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Help & Guidance. , Please ! .

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D.A.Godley12/11/2020 19:29:12
120 forum posts
39 photos

i have , for many years , wanted to construct a clock , however , I allowed myself to be sidetracked and have , as a result , spent a lot of years building locomotives.

Recently ,whilst visiting an Abbey, I was taken by the relative simplicity , but beauty, of its clock design and movement , which stirred the past longings .

In consequence of the above , I have copied the series by Alec Price detailing the Half size Turret Clock( E in M. 2001 ) , lodging this as my next project ( when other items are completed)

My initial request for help revolves around the several pinions which are required , specifically, 8 tooth pinions . I understand that for pinions with only 8 teeth , a special cutter is required at , for a novice likely to have a problem while machining the item , Costly ! . There are , I am sure you experienced constructors will know , very economically priced cutters available, but only cutting down to 10 teeth , which brings me to the burning question , Is it possible to use one of these to cut the 8 tooth pinion somehow ? .

Michael Gilligan12/11/2020 19:53:59
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20052 forum posts
1040 photos

When your Abbey clock was constructed, the pinions would have been filed by hand ... so anything’s possible.

We are spoiled with a fancy cutter for everything !

An alternative would be to use Lantern pinions.

MichaelG.

Martin Kyte12/11/2020 21:03:53
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2721 forum posts
48 photos

I remember Alec's clock at a show. Very interesting it was too. Birdcage frame if I remember correctly. I also went to a lecture by him on clock wheel cutting, he was a great advocate of making his own cutters so you may like to have a go too. Tooth form is much less of an issue on a turret clock as within constraints friction is much less of a worry. After all within limits you can add as much weight as you wish as the overall construction is much more robust than even a longcase clock. Lets face it tower clocks probably lean towards blacksmithing than horology at least in the early forms and I mean no disrespect by that. Another option for pinions would be to make a form tool and plane them. If all else fails as Michael Gillingham has suggested there is always lantern pinions.

best regards Martin

bernard towers12/11/2020 21:11:40
568 forum posts
109 photos

I made the Wilding Turret Clock and made the cutter for the wheels it turned out to be fairly easy, the pinions are lanterns which personally I think look more interesting but good for a turret as there is plenty of room for the dirt to go! I also cast the brass for the wheels which was interesting.will put some pictures in my album.

D.A.Godley16/11/2020 10:09:05
120 forum posts
39 photos

Thank you to those who responded , and I will take account of the suggestions , however , I have serious doubts about my ability to make the cutters . Understanding the geometry of the various drawings and diagrams of cutters which I have discovered on the Internet is quite daunting, let alone actually making one .

A little more ( as in A Lot ) of reading is called for I think ! , and perhaps some experimenting? .

Bazyle16/11/2020 10:52:05
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6295 forum posts
222 photos

When teh range of teeth is quoted for a cutter it is not a rock solid limit where the resulting teeth fall apart. The cutter is optimised for the middle of the range to save having to have a specific cutter for every tooth count. A production company would make the exact cutter they needed of course. So a 10 tooth cutter will still work for 8 but just be sub optimal resulting in a little more friction and wear over 20 years. You can always re-use pinions from an old clock and there are some places that provide cut wheels for the common amateur designs though I don't know about this one. You could also contact your local branch of the BHI many of which are currently still meeting by zoom and someone might have a spare part.

Nigel Graham 216/11/2020 11:12:08
2009 forum posts
27 photos

I don't know if you have looked at Ivan Law's book Gears and Gear Cutting (Special Interest Model Books, Workshop Practice Series, No.17).

He includes and explains the basic, most important geometry from first principles; whereas full treatises on gear theory dive straight to oceanic depths of complexity; and generally, considerably de-mystifies the subject of designing and making spur, bevel and worm-gears.

One chapter and shows how to make gear-cutters, both single-point (fly cutters) and multi-tooth. Now, this is for involute teeth and I do not know if your clock uses that or hypocycloidal forms - or whether it matters in the light of others' comments here.

(I think, but am not sure, that hypocycloidal-tooth wheels are the usual in small clocks, as the shape loses a little strength but more importantly reduces friction, compared to involute shape. You can't mix them though, in any application - excepting the lantern-pinion oft found in clocks, gears of any given pitch, tooth-form and pressure-angle will mesh only like-for-like.)

++++

As a digression from the lantern-pinion with its rod-teeth, for anyone modelling certain types of very old equipment; some such as manually-operated cranes and horse-gins, made cheaply for rough work, used a very crude tooth-form commonly called hollows and rounds. The tooth tips and roots were hemi-cylinders meeting tangentially on the pitch-circle, simple to make but incapable of transmitting much power and then only at low speed, with considerable friction and jarring. That was not from cost and difficulty in precisely cutting metal to cycloidal shapes, in their day. Instead, despite the illusion given by the shape, hollows-and-rounds teeth do not roll on each other as involute and related teeth do, but slide with changing velocity ratio.

The Classical Greek orrery, the Antikythera appears from the photos, to have triangular teeth - but that beautiful instrument still worked!

David Noble16/11/2020 13:25:35
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308 forum posts
15 photos

As a very new clock maker, I would recommend 'Wheel and Pinion Cutting in Horology' by J. Malcolm Wild. He explains very clearly how to make the cutters. I have found it hugely helpful.

David

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