John Wilding 8 day Weight Driven Wall Clock

[BizibilderParticipant @bizibilder]

The Pallet nibs are deliberately drawn and cut out very slightly oversize (as stated in the book). The pallet will not work to start with but as you refine the pallet action it is necessary to file away a tiny bit on each pallet nib in order to get them to work. You do this without changing the depthing.

[roy entwistleParticipant @royentwistle24699]

As Bizibilder Says, work on the pallet nibs but remember to work on right hand side of each nib only as drawn in 2 above

[Stephen BensonParticipant @stephenbenson75261]

This how I did my JW 8 day clock pallets, it was a long time ago now but the clock is still running well so I must of got something right

[Alan CharlestonParticipant @alancharleston78882]

Thanks for the help. One of the problems I struck was that the book says that the line GH shown in drawing 2 should pass through C and between F and D. It doesn't specify how it should pass between F and D. I have therefore drawn GH such that it passes through a point midway between F and D and generated a drawing of the pallets which I have printed and glued to a piece of 1/16" brass. I'll follow Bob Stevensons advice and see how I get on.

Thanks again,

Alan

[Alan CharlestonParticipant @alancharleston78882]

Hi,

After waiting for weeks my 0.2mm slitting saw finally turned up so I have been able to cut the slots required to get the pendulum installed. It's amazing how the suspension spring lets the pendulum oscillate for a couple of hours when it's set in motion.

I now need to install the crutch. The book gives the dimension of the slot which goes around the upper block as 3/16" which is the same as the upper block. In my case, this has resulted in a tight fit. Am I right in thinking that it should be a loose fit with the slop taken up by the adjustable shim? If so I'll file the crutch slot out.

Does anyone have any photos of the way the upper block fits into the crutch?

I've made the pallets, so once I've got the crutch sorted out I can look at putting everything together and see if it ticks. Exciting times indeed!

Regards,

Alan C.

[Stephen BensonParticipant @stephenbenson75261]

You need about 0.1mm (4thou) minimum clearance on the block just file it as it is not very critical but both the slot and block need to be polished, I made mine adjustable because I did not know any better but since then I have seen longcase clocks working well with twice that clearance, too big is better than too small.

[Alan CharlestonParticipant @alancharleston78882]

Thanks Stephen – Just what I wanted to know.

Regards,

Alan

[Russell EberhardtParticipant @russelleberhardt48058]

Posted by Alan Charleston on 15/03/2017 06:27:45:It's amazing how the suspension spring lets the pendulum oscillate for a couple of hours when it's set in motion.

Yes, nearly 99% of the energy loss in a free swinging pendulum like that is due to air resistance.

The way to measure the Q (quality) factor of a pendulum is to set it swinging at a measured amplitude. Time how long it takes to decay to 37% of that amplitude. You can then work out the number of swings it has made. The Q is then given by Q = 2 x pi x n where n is the number of complete swings (2 seconds for a seconds pendulum!). A good longcase clock pendulum should have a Q factor near to 10,000.

Russell

[Alan CharlestonParticipant @alancharleston78882]

Hi Russell,

Thanks for that. Just to clarify, does the Q factor of 10,000 applies to the pendulum alone – without the crutch?

Also, pardon my ignorance, but is the amplitude the horizontal distance the pendulum travels or is it the angle it moves through?

Another couple of extra questions,

I have had the pendulum oscillating with the crutch and pallets operating the freewheeling escape wheel. The pallets made the escape wheel rotate backwards. Does this mean I've got the pallets about right?

I haven't attached the wheels to their shafts yet. John Wilding recommends Loctiting them in place but I think I would prefer to slit the arbors and fit collets to compress them onto the shafts as he recommends for attaching the crutch to its' shaft. I can then adjust them to where I want them to sit easily. Is there any reason why I shouldn't do this?

Thanks again,

Alan C.

[Stephen BensonParticipant @stephenbenson75261]

I used Loctite 638 retainer and continue to use, Loctite is not permanent if you heat it up with a flame it will release easily I often loctite milling cutters into bespoke holders they will take a full cut but you can replace them when they wear out.

Adding weight to the train should be avoided but on this clock there is loads of spare power so it should not be a problem.

[roy entwistleParticipant @royentwistle24699]

Alan C From what you say I would suggest you have a good chance of your pallets being very near

I would also Loctite the other wheels to the arbors

Roy

[Russell EberhardtParticipant @russelleberhardt48058]

Alan,

The amplitude can be either the linear or the angular displacement. For small angles (say less than 5 deg) they are linearly related.

The Q factor of the pendulum is for the pendulum and suspension alone. You shouldn't let it swing connected to the escapement with no drive on the clock. You run the risk of the pallet hitting the tip of an escape wheel tooth and damaging it. However it sounds as if yours is OK.

I also use Loctite 638 but do be sure that you degrease thoroughly beforehand. If the adhesive lets go in use the weight will descend at high speed and can damage the mechanism as a result. The crutch needs to be adjustable to put the clock in beat.

Russell.

[Jim CParticipant @jimc]

Hi,

On the subject of Loctite. I have bought the pinions for this clock (not having made the lantern ones described in the build notes) and as a consequence they do not have shoulders for connection to their respective wheel. Do you think that Loctite will be adequate to fix the wheel and pinion to the arbor or will some pinning need to be done? (not much room in the pinion for this). Any suggestions gratefully received.

Thanks, Jim

[Russell EberhardtParticipant @russelleberhardt48058]

The traditional way of fixing a pinion direct to a wheel would be to turn a shoulder on the end of the pinion to be a tight fit in the wheel bore and a about 10 thou longer than the thickness of the wheel. The pinion is then pressed into the wheel and the protruding part opened out with a conical punch. An alternative is to use a star shaped punch which gives a somewhat more secure fixing. You do have to be careful to maintain cocentricity.

Russell.

[Alan CharlestonParticipant @alancharleston78882]

Thanks for all the comments. I'll follow the advice and Loctite the wheels in place. It's interesting the general opinion favours using Loctite 638. Wilding recommends 601 in the book – but that is more than 25 years old now, so I'll go for the 638.

I'm worried about using Loctite as I've had problems in the past when I've mucked about too long getting the position right and having a piece freeze in the wrong position. I think I'll make a 1/2" OD/ 3/32" ID collet bored out to say 1/4" 6mm from one end and use this to position the wheel on the shaft before adding the Loctite. I can then apply the glue to the shaft and slide the wheel into position up against the collet with no delays. The bored out end will stop the wheel sticking to the collet.

Regards,

Alan C.

[roy entwistleParticipant @royentwistle24699]

I wouldn't Loctite the wheel to the pinion. If there is room I would make a collet for the wheel and fasten that to the arbor at the side of the pinion

Roy

[Russell EberhardtParticipant @russelleberhardt48058]

Posted by Alan Charleston on 19/03/2017 05:37:34:

I'm worried about using Loctite as I've had problems in the past when I've mucked about too long getting the position right and having a piece freeze in the wrong position.

Both 601 and 638 will give you about ten minutes in which to adjust the position before the curing starts to take effect. That should be plenty.

Russell

[Stephen BensonParticipant @stephenbenson75261]

Posted by Russell Eberhardt on 19/03/2017 10:48:12:

Posted by Alan Charleston on 19/03/2017 05:37:34:

I'm worried about using Loctite as I've had problems in the past when I've mucked about too long getting the position right and having a piece freeze in the wrong position.

Both 601 and 638 will give you about ten minutes in which to adjust the position before the curing starts to take effect. That should be plenty.

Russell

I use Loctite SF 70663 degreaser and I have found Loctite 638 grabs a lot quicker than that I get about 20 to 30 seconds but maybe my bottle is getting close to its sell by date or it may depend on the gap 

Edited By Stephen Benson on 19/03/2017 11:02:26

[Russell EberhardtParticipant @russelleberhardt48058]

Posted by Stephen Benson on 19/03/2017 10:59:39:I use Loctite SF 70663 degreaser and I have found Loctite 638 grabs a lot quicker than that I get about 20 to 30 seconds but maybe my bottle is getting close to its sell by date or it may depend on the gap

It does depend on both temperature and the gap thickness. I keep my 638 in the fridge.

Russell

[Dick HParticipant @dickh]

A couple of points:-

Loctite 638 is an anaerobic adhesive, i.e. it cures when you exclude air (oxygen).

According to the data sheet (**LINK**) the best temperature to store this stuff is 8-21°C.

i.e in a bag in a fridge might not be best.

Sorry I´m a chemist.

Dick.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Dick H on 19/03/2017 14:41:14:

A couple of points:-

[…]

i.e in a bag in a fridge might not be best.

Sorry I´m a chemist.

.

Dick,

I agree regarding storage temperature, but; the sealed bottles contain sufficient air to keep the product liquid … so I don't really see the objection to a bag.

[apologies if I have misinterpreted your comment]

MichaelG.

.

P.S. … Good to have a chemist on board: Prepare yourself for lots of questions.

[Russell EberhardtParticipant @russelleberhardt48058]

Posted by Dick H on 19/03/2017 14:41:14:

According to the data sheet (**LINK**) the best temperature to store this stuff is 8-21°C.

i.e in a bag in a fridge might not be best.

Sorry I´m a chemist.

I understand why it should not be stored at high temperatures as a general rule of thumb is that chemical reaction rate doubles for every 10 °C rise in temperature.

Can you explain the problem with low temperatures? Is it just that it becomes too viscous to fill small gaps or is there a more fundamental problem? Will 5 C in a fridge really be a problem compared to 8 C?

Don't apologise for being a chemist. I used to enjoy making explosives when at school. Would probably be arrested for it now! The highlight of school chemistry was when our teacher was sacked after setting light to hydrogen in a glass flask rather than a gas jar and showering the front row with glass fragments!

Russell

[Dick HParticipant @dickh]

The material is described as a urethane methacrylate. This is probably also moisture sensitive (depends on how/if the molecule is "capped". In any case it described as "anaerobic", so putting it a bag in a fridge might restrict the amount of air it comes into contact with, i.e. it will start to cure. On the other hand it might attract moisture, also not good. As to the difference between 5 and 8°C, go out on a cold morning and see when you can see your breath condense in the air when you exhale. All of these data sheets from manufactures tend to the cautious.

What you say about "chemical reaction rate doubles for every 10 °C rise in temperature" (Arrenhius) is a rule of thumb, it depends on the activation energy of the reaction and whether it is endothermic or exothermic.

This stuff comes in a bottle designed to allow air in to stop it curing prematurely but perhaps keep moisture out. I´m not sure whether throwing the bottle in the drawer is better than sticking it in the fridge.

The viscosity in use shouldn´t be a problem, its just the shelf life and storage.

In any case most methacrylates depolymerise if heated to ~150°C, so the polymethacrylate bit can be softened and will decompose with gentle heating (work in an open, well ventilated area ).

[Dick HParticipant @dickh]

PS: The "cure mechanism of an anaerobic adhesive (or anaerobic sealant as they are often referred to) is triggered when it comes into contact with a metallic surface. This will cause the anaerobic adhesive to gel and cure. To facilitate full cure, the anaerobic adhesive needs to have exclusion of oxygen in combination with contact with a metal. With both these boxes ticked, the reactive molecules inside the liquid adhesive become activated which triggers the curing mechanism, causing the monomers to polymerise and create a solid". (From Permabond´s website).

As to the lower limit on storage, it could have any number of reasons. Moisture sensitivity, bits of the mix might crystallise out. etc.etc…

These adhesives are a mix of lower and higher molecular weight components which polymerise to make a crosslinked solid.

[Alan CharlestonParticipant @alancharleston78882]

Hi Dick,

Good to hear from a fellow chemist. In the past I had a tube of Loctite in the fridge for over 10 years and it seemed to last OK. I figure that if the recommended storage temperature range is 8 – 21C, it's better being in the fridge at say 4 – 5C than at ambient which can be from say 5 – 30C here. The relatively stable fridge temperature will reduce the propensity for the bottle to breathe as well.

Regards,

Alan C.

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