no recoil

[BoldminerParticipant @boldminer]

I have been trying for two weeks or so now to get this clock to run. All the pivots are polished and free in their respective holes, the train falls from side to side with the 'audible click' the arresting faces of the escape pallet have been brought to a mirror finish as have the corresponding faces of the escape wheel. The spring barrel is free to rotate on its' spindle, the pallet arbor is free and the clock set in beat using an ' amplitic' audio device. When set going there doesn't appear to be any force in the escape wheel that would result in a recoil action sufficient to maintain the momentum of the pendulum. The only thing that I can find at odds with the designed plan is that the spring purchased from Rite-Time for this model does not conform to the spec. quoted by J.W. ie it is aprox. 60thou. down on width. With the escapement disconnected and just one turn on the spring the clock will 'free wheel' for the equivalent of 36hrs. or so, with the escapement engaged ( with several turns on the barrel ) it will not run passed the naturally decayed swing of the pendulum. ANY IDEAS PLEASE ?

[BoldminerParticipant @boldminer]

J W’s great wheel clock

[Michael GilliganParticipant @michaelgilligan61133]

Sorry, I won't have chance to contribute any ideas today, but, for the benefit of other participants here's an overview: **LINK**

http://modelengineeringwebsite.com/Large_wheel_clock.html

MichaelG.

[Russell EberhardtParticipant @russelleberhardt48058]

It's not the recoil that drives the pendulum. In fact it's the pendulum that drives the recoil! Some designs of escapement have no recoil at all. Which of J.W.'s designs is your clock?

If the spring is the wrong width have you also checked it's thickness? That is more likely to give lack of driving power if wrong.

What have you used for lubrication? Are the pallet faces lubricated? A common problem is too much oil on the pallet faces.

Russell

[John HaineParticipant @johnhaine32865]

Russell is correct, but looking at the relevant Clickspring video this is essentially an anchor escapement with a small amount of recoil. Do you mean recoil in the technical sense, or impulse? Recoil is the action whereby the pendulum overswing forces the escapement wheel to turn backwards, which actually absorbs energy from the pendulum which is given back with interest slightly later.

When you apply "several turns" on the barrel, what percentage of winding is that? What if you fully wind?

One thing to try is to see if the clock will run when you apply a greater torque to the train than the spring can, either manually or by a weight.

[John HaineParticipant @johnhaine32865]

Deleted double post…

Edited By John Haine on 09/08/2018 12:07:24

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Russell Eberhardt on 09/08/2018 10:35:39:

Which of J.W.'s designs is your clock?

.

I had deduced from the thread sub-title that it was this one, Russell : **LINK**

https://www.bonhams.com/auctions/18836/lot/267/

Great Wheel was assumed = Large Wheel

[of course I may be mistaken]

MichaelG.

Edited By Michael Gilligan on 09/08/2018 23:57:01

[BoldminerParticipant @boldminer]

Many thanks to Russell, John and Michael, I will try to respond to your posts in order but please bear in mind that I am in no way an horologist or experienced clock maker. RUSSELL, my apologies, the clock is a John Wildings 'large Wheel' clock. The spring thickness does conform to the suggested thickness of .40mm . I have tried the movement with the pallet nibs both wet (not excessive) and dry using 'clock oil' from Meadows and Passmore, all to no avail. JOHN, there is no recoil what-so-ever on the escape wheel. I have tried the clock fully wound but don't get any improvement at all. I have also applied extra torque by increasing the pressure on the large wheel but all that seems to achieves is a louder click as the pallets engage with the escape wheel, incidentally the pallet drop is approx. 30% of the escapement tooth. MICHAEL, you are of course correct, the clock is a John Wildings' Large Wheel clock. Thanks to all, Colin Standish Ps. excellent video !

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Boldminer on 09/08/2018 05:50:07:

… The only thing that I can find at odds with the designed plan is that the spring purchased from Rite-Time for this model does not conform to the spec. quoted by J.W. ie it is aprox. 60thou. down on width.

.

If the spring thickness is to spec. and given that you have tried the extra checks that John suggested … I very much doubt if the reduced width is of significance.

It seems more likely that there is some undetected error in the set-up of the escapement.

If you have suitable equipment to hand … some detail photos of that area would be helpful.

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

[ Update ]

For convenient reference, here is a frame-grab from that excellent Clickspring video:

.

MichaelG.

[BazyleParticipant @bazyle]

I suspect that the impulse face of the pallet, or at least one of them, is a curve whose centre is the pivot instead of offset as in the diagram above. This means it cannot receive any impulse and also means you will not see any recoil. The recoil happens because after contact between pallet and tooth the continued swing of the pendulum pushes the tooth back.

In the diagram above that happens if you imagine the left hand pallet moving from its present position to a point where the contact is that little arrow is on the end of the 'R12 line'. To do this the tooth will have to have moved to the left, anticlockwise, which is the recoil. Then as the pendulum swings back the tooth is moving clockwise ending up further round from where it first made contact. It is this part of the wheel movement that imparts energy to the pendulum. The additional rotation that happens as it drops from one pallet to the other is wasted energy which is why you try to keep it as small as possible.

The pallet face does not have to be curved, it can be flat, so you could try an 'all or nothing' approach of filing it slightly to an appropriate angle to see if it helps. You would likely have to remake the pallets anyway.

[michael mParticipant @michaelm]

Lack of recoil will not stop the clock from running, many escapements are designed without recoil at all and some with a minimum amount. In the case of the anchor escapement such as yours it would however cause poor time keeping. Given that your clock is only running for the period of the pendulums natural decay I would suggest, as has already been touched on, that the problem is lack of impulse. If the movement is free running and there's adequate side play on the arbors you may have to re-check the pallet geometry. If, as already commented on, the pallet face is radial to the pallet arbor then no impulse will be given. Filing metal from the pallet may facilitate some degree of impulse but it will be very small, that's why clocks with worn out anchor pallets are only capable of small and unreliable pendulum amplitude. It will also create excessive drop. Although it's necessary for reducing friction and wear in a working movement, if a new movement will not work without oil on the pallets there is an underlying problem. Arbitrarily attacking the pallets with a file is likely to finish you up in the madhouse so I think you should carefully study the pallets you've made and consider making a replacement set.

[John HaineParticipant @johnhaine32865]

Yes, though recoil is a side effect of how the anchor escapement works it is a sign that it is doing the right thing. If the pallet faces are circular arcs and there is not recoil it shows that the axis of the arc is in the wrong place. I fear the solution most likely to succeed is to make a new anchor.

[Dick HParticipant @dickh]

How smooth are the faces of the escape wheel teeth? I assume everything has been polished. Look at the points of the escape wheel teeth, they shouldn´t be too sharp. However carefully you cut the escape wheel you might have to spin the wheel in the lathe and apply a fine file to the tips of the teeth.

Before you start to cut metal again, has this design got an eccentric pivot for the arbor holding the anchor? If so, have you tried adjusting the amount of engagement?

If you have made the little depthing tool that John Wilding advocates, check the anchor. In MichaelG´s frame grab the distance between the tips of the exit and entry pallets is five and a half teeth.

Having once assembled an escapement mirror inverted, don´t ask me how, corrected it and fiddled around bending anchors and filing away until there was no alternative but to make a new anchor,I can give 1 vote for Michael m´s comment that "Arbitrarily attacking the pallets with a file is likely to finish you up in the madhouse "….

PS. Bazyle -Very nice explanation.

[Russell EberhardtParticipant @russelleberhardt48058]

O.K. It's a standard anchor escapement. Assuming that the pallets are made to the correct dimensions the only adjustment to make is the distance from the escape wheel arbor to the pallet arbor. Not sure if there is adjustment available on that clock but it sounds as if it should be a bit closer to give the recoil.

The Medmaw clock oil should be fine. The very smallest amount is needed on the pallet faces. Just enough to reduce friction but not enough to introduce significant drag. I apply a drop with a pin and then wipe most of it off with a lint free tissue.

Russell

[michael mParticipant @michaelm]

Whilst appreciating that all advice is well intentioned I do feel that some comments are ether gratuitous or ill-considered.

The OP has already discovered that oil won't make a faulty clock run. It wouldn't, no matter how administered.

The OP has told us that drop is 1/3 of the tooth thickness. Assuming a tooth thickness of .015" which would be reasonable then the drop would be some .005". All else being OK the clock would run. So shortening the pallet arbor and escape wheel centres may reduce an already tiny drop but won't alter the impulse faces. That's not the function of that adjustment. (Assuming it exists on that clock). Agreed it is done by poor repairers in an attempt to compensate for worn pallets but is a poor bodge and affects the overall escapement action.

The OP has told us that the pallets and wheel teeth have been brought to a mirror finish. Polishing the wheel teeth may not be advisable on a first build given the risk of affecting the tooth profile for minimum benefit on an anchor escapement.

Filing the escape wheel teeth in the lathe is I think risky advice for someone new to clock making. The teeth are delicate. Does he have a suitable file? I appreciate it's done but normally to correct an inaccurate or damaged escape wheel, not to try and compensate for an innacurate pallet. Given his small drop it's unlikely there's a proud tooth or it would manifest itself by catching on the pallet and he'd be aware of a short tooth skipping through. If he succeeds in accurately reducing the diameter of the escape wheel then he's upset the whole escapement geometry and a new made perfect pallet may not work. He's now introduced a second variable. What's he to do then? Bend the pallet arbor?

Anchor escapements are incredibly tolerant of wear and abuse and the fact that this clock fails to make any attempt to run suggests that there is a radical fault in the manufacture.

I concur with John Haine who has summed it up thus "I fear the solution most likely to succeed is to make a new anchor"

You could initially of course make one more easily from aluminium or brass as a try out before going for carbon steel.

[Dick HParticipant @dickh]

Sorry to muddy the waters.

If you look at the Clickspring video on YouTube (How To Make A Clock In The Home Machine Shop – Part 20 – The Crutch Assembly And Eccentric Bushing) **LINK**.

The eccentric bushing and the clamping screw for the crutch are nicely illustrated in the first 20-60 s of the video.

In the absence of any analysis, I fear the solution proposed "to make a new anchor" without knowing what was wrong with the previous one and where the fault lies is just tapping in the dark.

Has it been put together too tightly, does it rattle? If you run the clock without the escapement engaged does it still whizz round if you gently squeeze the front and back plates between your thumb and forefinger?

[John HaineParticipant @johnhaine32865]

Dick, those points have been covered. There's a direct observation that there's no recoil which would be consistent with at least one of not both impulse faces being on the wrong centre.

[BoldminerParticipant @boldminer]

Michael G, Bazyle , Michael M, John Haine, Dick H and Russell, once again thank you for your support and assistance and again in order of posting :- Michael G that screen shot is a great help and will be used to produce a new anchor. Bazyle thank you for the explanation of the 'proc cess' it has gone a great way to lifting the fog that surrounds the black art. John Haine I really do appreciate you help and advice. To clarify my information about 'the drop' the pallet nib drops approx. 30% down the face of the escape wheel tooth. The face of the teeth were not attacked with a file, merely polished with Crocus paper and still retain their flat tops. Dick H the clock is fitted with an adjustable eccentric, the use of which has been tried (to no avail) , all the arbors do 'rattle' from side to side and the free wheeling action is not impeded by pinching the frames. Russell as I explained to Dick H., there is an eccentric and has been tried, but I must admit that I did not wipe the residual oil from the pallet nibs (will do in future). So gentlemen, after reading your comments I think that the obvious way forward is to produce a new escape pallet with the help of Michael Gs' screen shot and to double check the other relevant dimensions, many thanks , watch this space ! Colin

[Russell EberhardtParticipant @russelleberhardt48058]

Good luck!

Russell

[David NobleParticipant @davidnoble71990]

As an interested spectator to this thread, do you have an update?

David

[martin perman 1Participant @martinperman1]

Posted by David Noble on 05/08/2019 17:09:04:

As an interested spectator to this thread, do you have an update?

David

+1 here, I've just read the complete thread where I started out with it all whistling over my head and ending up with knowing a little about how a clock works, I recently bought a 1940's ish pendulum wall clock which quietly ticks away in the hall and I admit to watching it trying to see what makes it tick.

Martin P

[Chris TickTockParticipant @christicktock]

Hi, this old thread is currently of great interest to me. The question I would like answering is this and it may well be more targeted at those familiar with clocks and / or physics;

does the recoil transfer any energy to the escape wheel. it is argued by some that turning the E.W backwards which impacts on the time train down to the weight that this energy is then added to the forward driving impulse as the anchors pallets slide off the E.W's tooth.

I have asked this on a watch forum, many readers but no replies. I have google this but get nothing firm.

My take is as the force exerted turning back the E.W at the point of the anchors maximum travel is latched by the force in the pendulum. There can be no impulse force acting at this stationary point. but as the pendulum then starts its fall due to gravity the E.W helps it on its way but is there additional energy to what there would be ordinarily at this point due to recoil. Or on the other hand has it been used up resisting and bringing the E.W to a stop.

The issue to me is many writers have stated recoil is a disadvantage due to wear and wasted energy. Whilst wear is obvious is wasted energy, not if the recoil helps propel the anchor?

Chris

[John HaineParticipant @johnhaine32865]

Oh dear. Recoil happens as the anchor drives the escape wheel backwards just after the impulse. If there is a seconds hand attached to the escape wheel arbor you see it move backwards a little just after it jumps forward. The impulse is delivered at that jump forward. The train is, somewhere, absorbing energy from the pendulum – how much goes where depends on many factors such as play in the pivots and various other things. Some might even slightly raise the driving weight. With luck most of the recoil energy will be delivered back to the pendulum, but if things are worn and or inaccurate maybe not. The level of escapement error is also determined by the recoil (amongst other things) so wear etc that changes the recoil changes timekeeping.

The Graham deadbeat escapement has no recoil as its name implies, so no energy is extracted from the pendulum by recoil.

Harrison's Grasshopper is very good at returning the energy especially if it has a remontoire, and recoil is an important aspect of his clocks' operation. Many gravity escapements inherently have recoil, in that the pendulum picks up a weight before it reaches maximum swing, "recoiling" it, then the weight is taken off the pendulum at a lower level by a stop and is then returned to the higher level by some sort of mechanism.

[Chris TickTockParticipant @christicktock]

Posted by John Haine on 29/02/2020 15:46:09:

Oh dear. Recoil happens as the anchor drives the escape wheel backwards just after the impulse. If there is a seconds hand attached to the escape wheel arbor you see it move backwards a little just after it jumps forward. The impulse is delivered at that jump forward. The train is, somewhere, absorbing energy from the pendulum – how much goes where depends on many factors such as play in the pivots and various other things. Some might even slightly raise the driving weight. With luck most of the recoil energy will be delivered back to the pendulum, but if things are worn and or inaccurate maybe not. The level of escapement error is also determined by the recoil (amongst other things) so wear etc that changes the recoil changes timekeeping.

The Graham deadbeat escapement has no recoil as its name implies, so no energy is extracted from the pendulum by recoil.

Harrison's Grasshopper is very good at returning the energy especially if it has a remontoire, and recoil is an important aspect of his clocks' operation. Many gravity escapements inherently have recoil, in that the pendulum picks up a weight before it reaches maximum swing, "recoiling" it, then the weight is taken off the pendulum at a lower level by a stop and is then returned to the higher level by some sort of mechanism.

 

Oh Dear john, you seem to have missed the point of my question;

Certainly recoil turns momentarily the time train back (in a jerky manner) observed by the second hand should the clock have one. But;

Once the energy or force from the pendulum has been overcome both the E.W and anchor stop before resuming forward motion. So is there at this point there any increased force applied to the pallet which has been increased by the recoil. Certainly recoil takes energy out of the pendulum by stopping it in recoil but has any additional energy been stored / added by as it were opposing a weight or spring driven train as the E.W resumes its forward rotation?

Chris

 

 

Edited By Chris TickTock on 29/02/2020 16:36:02

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