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Pallet drops and recoil.

Long case clock

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Hnclad11/12/2019 03:50:39
21 forum posts
5 photos

Hi.

I have just completed the going train of Allan Timmins 8day long case clock. I have set up the clock temporarily to observe the action of the escape wheel and anchor before progressing with the strike train and I have 2 questions. The first is "What constitutes excessive drop", my observation on the motion of the 'scape action leads me to think that there maybe excessive drop on the entering pallet, at least I have come to this conclusion based on the 'scape action on my previous clock, Wildings Elegant Skeleton Clock" which seems to have a smoother action. Although both the entering and leaving drop seem to be identical or very close, the entering pallet seems to drop heavily onto the 'scape wheel, or visa- versa .When I was filing up the pallets as I neared the scribe lines I cautiously filed each pallet until they released, I think I was as close as possible to perfection without risking a jam. A temporary paper hand on the 'scape wheel arbor shows some recoil but not much. This my second question how much recoil is enough and how do you measure it?

After depthing and assembling the 'scape wheel and anchor in the clock frames before attaching the pendulum, I put a little pressure on the 3rd wheel arbor and the escape wheel turned as the pallets oscillated just as they should. The clock has been ticking for 3 days without stopping and has the familiar tick-tock of a grandfather clock that I remember. I hate to start "adjusting" the drop if it is unnecessary and finish up damaging the escape mechanism. Any advice and guidance before proceeding would be appreciated.

Thank you David.

roy entwistle11/12/2019 14:46:08
1090 forum posts

Sounds like the pallets need lowering. ie. moved nearer to the scape wheel

There again if it runs OK why alter it ?

Roy

lfoggy11/12/2019 15:17:04
avatar
97 forum posts
9 photos

With a recoil escapement it is very difficult to completely eliminate drop but it should not be excessive otherwise the pallet face won't last and consistency will be affected. The drop will always be visible on careful inspection but should not cause a noticable visible jump forward in the seconds hand. As for recoil, there should be a clearly visible degree of recoil apparent on the seconds hand. Do you have a jig on which you can test the escapament and vary the distance between escape wheel and pallet arbor? This is very useful. You can then alter this distance to detmine the optimal positioning. If you haven't yet hardened the pallet you can gently squeeze it in a vice to reduce the distance between the pallet faces which can help as well.

Maybe post a video of your escapement in action?

Martin Kyte11/12/2019 15:17:59
1541 forum posts
24 photos

If the pallet arbor is on an eccentric bush then you could adjust. If it's not don't bother. I assume the clock is 'in beat'. Equal time from tick to tock as tock to tick? Your ears are better than your eyes for this.

regards Martin

Hnclad11/12/2019 20:29:12
21 forum posts
5 photos

Thanks to everyone who replied. I was extremely careful of the removal of metal at the end when the 'scape wheel finally cleared the pallets and the anchor oscillated. To test my accuracy while the wheel and pallets were set up in the simple depthing tool I closed the distance between the 2 arbors by 2 thou. and the mechanism jammed. So my dilemma is if I lower the pallet arbor surely it will jam on the wheel teeth, providing my depthing was accurate. I was very careful with the depthing, however I will machine some eccentric set screws and lower the back cock 5 thou to see what that does. Timmins suggests filing the screw holes in the back cock and then loosening the screws and tapping the cock to bend the fixing pins. This would be a last resort I think. As Ifoggy says there has to be some drop. As the exit pallet releases the wheel, a tooth and the entrance pallet are alined, so the wheel rotates as the entrance pallet drops it meets the incoming tooth. There is very little clearance between the entering pallet and the wheel tooth so I feel that any lowing will cause a jam. I must be missing something or being overly anxious. At this time the pallets have been hardened but the fixing pin holes haven't been drilled.

Regards David.

Hnclad12/12/2019 04:08:59
21 forum posts
5 photos

In the workshop this evening I decided to go ahead and lower the pallet arbor. To do this in a way that changes nothing that cannot be reversed, I turned a recess under the head of the set screws securing the back cock. The recess width was the thickness of the back cock feet. I had calculated that a 5 thou deep recess would lower the pallet arbor at the 'scape wheel location by a thou. After each 5 thou. increment I reassembled the pallet arbor and checked for drop on the entering pallet. I reached a recess depth of 25 thou. but ran out of shop time so I have the clock running to observe the drop. I had intended to keep deepening the recess until the pallet jammed and will continue tomorrow. At this setting the action is smoother, the entering pallet and wheel tooth meet in a more gentle way, there is less drop for sure and more recoil. The idea to go ahead with this was given to me in Ifoggy's reply, that the minute hand should not move in a visible jump. The light bulb went on, the minute hand mimics the interaction (drop and recoil) between the escape wheel and the pallets. Thanks for that. I'll report back after further adjustments. I can only say I am shocked by what I found. I thought I had made the pallets as close to perfect as was possible.

Thanks for everyone for your help.

Regards. David.

lfoggy12/12/2019 07:03:39
avatar
97 forum posts
9 photos

Sounds like progress !

In my expereince it is virtually impossible to achieve an optimal escapement by hand filing or machining to a scribed line. You always need to do some adjusting. How long you spend adjusting depends on how much of a perfectionist you are.....

roy entwistle12/12/2019 08:28:34
1090 forum posts

I fully agree with Ifoggy. You can't use measurements and marking out on a clock. I can't anyway

And I was told ' Drop in, squeeze out' ie. lower to adjust entry, squeeze to adjust exit

Roy

roy entwistle12/12/2019 21:48:06
1090 forum posts

Incidentally I wouldn't harden either pivots, pinions or pallets before I got the clock working properly

Roy

Hnclad16/12/2019 11:13:12
21 forum posts
5 photos

I have taken a video of the escapement in action but find that only JPG files can be uploaded. Can you help?

David.

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