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Drop on recoil escapement

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Chris TickTock16/10/2020 09:20:24
605 forum posts
43 photos

Hi Guys,

One for those with a horological bent.

I am attempting to brush up on recoil escapement design. Gazeley states in laying out a drawing for a 30 tooth E.W that you start off with the 360/30 spacing giving 12 degrees. Then you allow 1 degree for tooth tip metal...fine so far. Then he goes on to say a further 12 degree is allowed for drop. This confuses me looking at his drawing does he mean add a further 1 degree to the tooth tip making the tooth tip 2 degrees or does he mean something else?

Regards

Chris

Chris TickTock16/10/2020 14:29:42
605 forum posts
43 photos

Error in my post (sorry, rushed it while going out) it should read:

I am attempting to brush up on recoil escapement design. Gazeley states in laying out a drawing for a 30 tooth E.W that you start off with the 360/30 spacing giving 12 degrees. Then you allow 1 degree for tooth tip metal...fine so far. Then he goes on to say a further 1 degree is allowed for drop. This confuses me looking at his drawing does he mean add a further 1 degree to the tooth tip making the tooth tip 2 degrees or does he mean something else?

I think he means leave a 1 degree gap for slack in the system but not as yet sure.

Regards

Chris

SillyOldDuffer16/10/2020 15:14:24
Moderator
6437 forum posts
1419 photos

What I know about recoil escapements is miniscule, so what follows is a wild guess.

recoil.jpg

The white lines are the 12° markers, with the green lines offset by 1° and blue by 2°. Red is the tooth form.

I think he means as in tooth B, where the top is 2° and the steep side comes back to the root. The form shown at A makes the tooth a little stronger but less positive for the anchor to catch and easier for it to release. Now I'm completely out of my depth!

Dave

Chris TickTock16/10/2020 17:19:19
605 forum posts
43 photos
Posted by SillyOldDuffer on 16/10/2020 15:14:24:

What I know about recoil escapements is miniscule, so what follows is a wild guess.

recoil.jpg

The white lines are the 12° markers, with the green lines offset by 1° and blue by 2°. Red is the tooth form.

I think he means as in tooth B, where the top is 2° and the steep side comes back to the root. The form shown at A makes the tooth a little stronger but less positive for the anchor to catch and easier for it to release. Now I'm completely out of my depth!

Dave

Dave, your post though appreciated ans well intentioned does not cut it with me, I could be wrong as I too am unsure.. I am referring to Gazely's clock and Watch escapments page 23.

The back side of the teeth are radial and the front concave. but Gazeley is simply stating the theoretical teeth spacing if a tooth came to a fine point is 12 degrees. As the action takesxplace over half a tooth this is 6 degrees. Then the theoretical 6 degrees is adjusted for 1 degree of metal on the tooth tip and 1 degree of drop to allow for running tolerances. Looking at his diagram I fail as yet to see where the 1 degree of drop comes in. The rear flank on his drawing just goes back to the centre of the E.W wheel so in this case no there is another explanation that 'escapes' us (pun).

Chris

John Haine16/10/2020 17:43:06
3422 forum posts
184 photos

Chris, I suggest that you find out exactly what is meant by "drop" in this context. In my experience many horological texts can be most obscure and often use terms which the author assumes everyone understands so are not defined in the text. I don't think that "drop" is there to allow for running tolerances, it's to make sure that the wheel is released by one pallet before the next engages.

Bob Stevenson16/10/2020 18:18:57
440 forum posts
7 photos

Gazeley is a 'work' of missguidance and thoeretical stupidity and should be chucked as soon as possible by any clock maker who wants to learn about escapements.....There!..I said it!

Five years ago when I was making Brocot escapements I was handed Gazeley as some kind of clock de3sign 'bible' but in fact, it's impossible to use Gazeley's descriptions to make a working escapement. He suggests that to understand any 'scapement one merely needs to draw it out using his layout,...however, this is IMPOSSIBLE to achieve using this crap book! My own copy now resides under the corner of a long-case that needed to be made upright! There used to be many members of my clock club who believed Gazeley to be the Word of God, but NOBODY has bee nable to draw the Brocot using his description and many have now seen this rubbish for what it is, namely, a massive wrong turn for any learning clock enthusiast.

The best and most easy text to understand (and confirm in practice) is 'Practical Clock Repair' by Don. D' Carle...see the lower half of page 135 (previous pages are also helpful) and use the described method to calculate required drop.

Chris TickTock16/10/2020 18:21:46
605 forum posts
43 photos

Thanks Guys for posts,

John you are so right that word drop can be confusing. I have looked hard now at Gazeley's drawing and his explanation. My conclusion is that his drawing is in error or at the least confusing.

Drop has to be free run and it is defined often as necessary to allow for mechanical tolerances. Adding this to a tooth tip would do the opposite. So whereas 1 degree is stipulated for the metal tooth tip I am fairly sure the 1 degree drop is not affecting the tooth design as such but the pallets.

Looking at his drawing the reason I think it is in error is that he shows 10 degrees marked which is split into 2 unequal sections with one marked 5 degrees. I assume he is starting the 5 degree larger section from the 1 degree drop. Thus the drop is not marked on the drawing which leads to a lot of confusion.

Chris

Chris TickTock16/10/2020 18:44:57
605 forum posts
43 photos
Posted by Bob Stevenson on 16/10/2020 18:18:57:

Gazeley is a 'work' of missguidance and thoeretical stupidity and should be chucked as soon as possible by any clock maker who wants to learn about escapements.....There!..I said it!

Five years ago when I was making Brocot escapements I was handed Gazeley as some kind of clock de3sign 'bible' but in fact, it's impossible to use Gazeley's descriptions to make a working escapement. He suggests that to understand any 'scapement one merely needs to draw it out using his layout,...however, this is IMPOSSIBLE to achieve using this crap book! My own copy now resides under the corner of a long-case that needed to be made upright! There used to be many members of my clock club who believed Gazeley to be the Word of God, but NOBODY has bee nable to draw the Brocot using his description and many have now seen this rubbish for what it is, namely, a massive wrong turn for any learning clock enthusiast.

The best and most easy text to understand (and confirm in practice) is 'Practical Clock Repair' by Don. D' Carle...see the lower half of page 135 (previous pages are also helpful) and use the described method to calculate required drop.

Bob,

I have always tried to have several books chiefly in case i don't understand the way one explains something it may click with another. I have also seen poor comments over other well known horological writers. I will add the book you suggest though...thank you.

Chris

blowlamp16/10/2020 19:53:30
avatar
1442 forum posts
97 photos

Just for interest, I recorded a video of a recoil escapement generated in Gearotic with various drop angles.

Martin.

John Haine16/10/2020 21:08:34
3422 forum posts
184 photos

An excellent video, showing why drop is needed to allow the escapement to operate - a good find Martin.

Rod Renshaw16/10/2020 21:21:18
195 forum posts
2 photos

+1 for the video. I am not a clockmaker but I have often wondered how an escape wheel gave impulse to a pendulum. it is obvious that it must happen, or the clock would stop, but I found it difficult to understand how from drawings.. The slow motion of the video makes it all very clear.

Rod

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