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Clock No. 2 AIP

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Yojevol

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Over the past year I have been plodding away with my 2nd attempt at making a wooden clock. I didn't record much of the making so I'll pick up on the project at this final stage hence AIP - Assembly In Progress. I've had the clock running on and off for the last couple of months and I've been taking time to sort out the inevitable little wrinkles which have causing minor deficiencies. Having optimised the pendulum length to give any accuracy within 1sec/min, I've now dismantled it and am giving it a last tidy up.
This clock is very different from my first clock. Although it has the same basic gear train, it is assembled in a completely different way in order to achieve its main design feature. It is also very 'thin' clock as compared with the Simplicity. All will be revealed it goes together. So here goes:-

The Frame
This is made out of 12mm veneered ply from B&Q. It is basically a solid product but occasionally you come across lumps of variable thickness which have been thrown in to fill possible voids. It's pretty obvious that the plys have been subjected to high pressure in a large press to squash them into a consistent thickness product. I bought it for my first effort and it has been a reasonable plywood to work with.

Frame.jpg


The main thing to watch out for in the glueing up was to ensure that the shaft holes were lined up properly (something I failed to do in the first clock). This time I inserted the 5mm brass shafts into their location holes to keep the 3 main elements in line.
Brian
 
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donwatson

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Thanks Brian. Another great piece of work and many thanks for showing. This may inspire me to start again but 'so much to do so little time'
Don
 

J-G

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You've given yourself a headache by selecting B & Q's plywood :) As you've found it is not the best quality but naturally it is at a particular price-point. It may well do the job so I can see why you would take that route, buying a full 8' x 4' sheet of Baltic Birch plywood from a reputable timber yard would probably be 3 - 4 times the price. Even specifying A/B grade would be 2 - 3 times the cost.

As far as aligning the spindle holes, it would be better to drill the holes slightly smaller than the finished size and then Ream the components after assembly -- ie. use (say) 4mm pegs to align the components for glue-up but then Ream out to 5mm Ø to suit the real spindles once the glue has cured.
 

Yojevol

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Did I say 1sec/hour above? No No No not at this stage. Now corrected at 1sec/min

Drive System
This design features a chain drive rather than cord and pulley, so the first thing I had to do was buy some chain so I could design a sprocket. The choice of suitable chain was severely limited and I had to settle for something rather heavier than I would have liked. Some years ago I bought some brass chain which would have been ideal but no sign of it now.
I felt that the minimum number of teeth on the sprocket was probably 5 so its circumference is equivalent to 10 links. It is made of a sandwich of the toothed wheel and 2 side plates which support the links between the teeth. The teeth have tapered tips so that they engage easily with the next link in the chain.
A ratchet wheel is attached to the sprocket and this transmits motion to the output drive gear via 3 pawls. This arrangement allows the drive weight to be raised easily. The ratchet wheel is a common source of failure on these wooden clocks as each tooth takes in turn the full force of the weight . On this clock I've made the ratchet much beefier than the Simplicity's which also has the benefit of being much easier to make.

Winder assembly.JPG



The output gear meshes with a pinion which is attached directly to the minute hand via its shaft (the far one in the above photo). Therefore the pinion rotates at 1rev/hour and, as there is a 8/32 ratio of gear teeth, the sprocket rotates once every 4 hours. This means the chain will drop 10 links, or 168mm, every 4 hours which is a very acceptable 1m over 24 hours.

@J-G The use of the 'cheap' 12mm ply certainly hasn't caused any headaches. I used it on the Simplicity centre wheel without any problem. The worst that happen is a cosmetic flaw as shown here:-

ply inclusion.jpg

The rest of the sheet has disappeared now - my daughter pinched for one of her projects!

On this occasion the method assembly has been quite satisfactory although I have had a problem with some of the shaft sockets being out of true. I've put that down to my old Sealey pillar drill having an adjustable angle table which could have been slightly out of true. Hopefully I've solved that problem by replacing it with a much older Startrite-Mercury drill with a non-adjustable table.

Brian
 
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Yojevol

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The Going Train
Why is it called the Going Train? I have been told that it determines where the energy from the driver is going.

It starts with the 1st Gear which in this case has 60 teeth and it is fixed to the shaft coming from the drive so it turns at 1 rev/hour. This drives the 2nd Gear via an 8 tooth pinion which gives it a rotational speed of 60/8 revs/hour. The 64 tooth 2nd Gear in turn drives the Escape Wheel via another 8 tooth pinion giving it a speed of 60/8 X 64/8 revs/hour. Lo and behold that works out as 60revs/hour or, amazingly, 1rpm. Each tooth of the Escape Wheel interacts with the Pendulum twice in in every rev, so as it swings each way once per second, the Escape Wheel has 30 teeth.

All these cogs are made from 6mm B/BB birch ply. This grade of ply has a good side and a not-quite-so-good side which manifests itself in a rougher sanded finish and possible knot repair patches. I'm happy for the BB side to remain unseen on the backsides of the gears. The only problem the plywood presented me with was a few little bits of face side veneer falling of tips of the slender Escape Wheel teeth. A fiddly job to make good.
My desire to make the clock as slim as possible gave me a bit of a problem on the 1st Gear. It has to be gripped to its brass shaft by a grub screw. Normally this is achieved by glueing a boss/grub-screw to the gear but that would add another 6mm to the overall depth. The ply is thick enough to accomodate an M3 screw but drilling down to the gear shaft bore between two spokes and with the outer rim in the way is nigh on impossible. My solution can be seen in the pics below - a seperate hub with the screw hole drilled prior to glueing it into the spokes.
The coloured spots are to ensure that the gears are assembled in a consistent relationship. There is a lot of assembling and dismantling in this process so it pays to keep thing as consistent as possible.

Gear assembly.JPG


Brian
 
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J-G

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Can't give you a definitive answer on the 'Going' but it's probably buried in antiquity as a means to differentiate it from the 'Chime Train' or the 'Motion Works' - being the train of gears that get the clock 'going'.

The Escape Wheel in the final image looks very good indeed - has it had a pair of black lines applied?

What is the point of maintaining the relationship of the gears to each other (coloured spots)?
 

Yojevol

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Can't give you a definitive answer on the 'Going' but it's probably buried in antiquity as a means to differentiate it from the 'Chime Train' or the 'Motion Works' - being the train of gears that get the clock 'going'.

The Escape Wheel in the final image looks very good indeed - has it had a pair of black lines applied?

What is the point of maintaining the relationship of the gears to each other (coloured spots)?
I think 'Going' could well be associated with energy release as the term 'Escapement' is the system which allows the energy to 'escape'. so I'm told!

Yes, the rim on the front side is painted black. All will be revealed tomorrow.

Re spots. When shaping the gear teeth by hand small errors in profile can cause enough sticktion to stop the clock. I had half a dozen instances on my first clock which needed a bit of fettling to free up the motion. Having got the whole train running smoothly it is advisable to keep the relationship consistent otherwise different set of tooth interactions might throw up more errors. On this clock I've had only one or two instances as my tooth profiling skill has improved.
Brian
 

J-G

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Looking more closely at your images, it seems to me that the larger gears are cut to an 'Involute' form whereas the Pinions are nearer a 'Cycloidal' form. It is more usual to use the cycloidal form for clocks since there is no need for 'power transfer' as such and since the gears always move in one direction 'backlash' becomes irrelevant so the involute form - which addresses both of these issues - is not beneficial, actually quite the opposite.

Using a cycloidal form with some 'play' would take away all the potential 'sticktion' so freeing up the need to maintain the mesh --- this is only maintained with the 64/8 pairing anyway, the 60/8 pairing means that all the leaves on the pinion will mesh with 12 of the teeth on the gear and after two turns will return to the first 8.
 

Yojevol

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Face & Hour Train

Face assembly.JPG


The Face and Hour Train form an assembly which is not fixed to the clock frame, it hangs on the minute hand shaft.
The face itself is made up of 2 rings - an inner and an outer. These were made from strips of bendy ply formed round circular patterns and stabilised with veneer strips inside and outside. The numbers are cut from 6mm ply and are glued between the two rings. A backing ring is covered with a decorative paper. A hanger is glued to the bottom of the inner ring and at its top end is a bearing which slides onto the shaft. At the bottom end of the hanger is a lead weight which helps to keep the whole assembly stable.

The Hour train consists of a 10 tooth pinion attached to the main shaft. It drives a 32 tooth gearwheel which has an 8 tooth pinion on the same shaft meshing with a 30 tooth gear. So the ratios look like this - 10/32 X 8/30 = 1/12, ie, the hour hand rotates once every 12 hours.

So let's put it all together and go for a spin:-


Did you like that as Fred Dibner would say.
Sorry I flicked the face a bit too violently :mad:

Just got to get the pendulum sorted and I think we're about there.
Brian
 
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J-G

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Clicking on the video [start] returns a "Video unavailable - this video is private" error. I got that when I first tried it on Sunday and hoped that it might have been due to you not having uploaded it but it still gives me this today.
 

Yojevol

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Clicking on the video [start] returns a "Video unavailable - this video is private" error. I got that when I first tried it on Sunday and hoped that it might have been due to you not having uploaded it but it still gives me this today.
Oops, first attempt to use YT 😡 Have changed video settings. Try again.

I've taken a couple of steps backwards recently. I decided to change the pendulum support from a bearing to a knife edge. Unfortunately the CG of the bob is not directly under the knife edge which causes it to hang backwards thus colliding with the drive weight 😰🥵🤯
Brian
 

J-G

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OK - now viewed the video thanks. Not sure I understand how the CG could be anywhere other than directly under the knife edge - unless the knife edge is not perpendicular to the pendulum rod -- or the clock is not vertical.

Rather than a knife edge I've used two single point screws as the pivot but also have an adjusting screw to make sure that the clock frame can be made to sit absolutely vertical. Walls are seldom 'near enough'.
 
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