Morbier Crown Wheel Escapement Help Needed

[MLSchlot]

I'm trying to restore a French crown wheel Morbier, and am having the devil of a time getting the escapement set up properly. I've checked and adjusted the crown for flatness, roundness, and tooth height. The arbor is true, but no matter how I adjust the locking depth of the pallets I can't seem to get it going. While slowly operating the escapement by hand, either both pallets catch and won't let the tooth get by, or the escapement runs away. I've checked the running of the crown in the lathe as-well-as in the movement; it looks as true as can be. With the pendulum attached and in beat (for the few consecutive teeth it will run on) the pallets are engaging equally, but the depth is very slight. I'm using 8 pound weights, and the train appears to be sound in all other respects. I can't believe adjustment of these movements is normally this touchy. I'm sure I'm missing something basic, but can't see it. Can anyone give me some ideas?

 

[eskmill]

The Morbier movements employing the "crown" escape wheel and verge palet escapement can be very fussy.

The design of the escapement demands lots of recoil. The fancy pendulums are compatible only with the more conventional and later "anchor" escapement.

The crown wheel-verge escapement movements nearly always used the folding pendulum with a small (about 9 ounce) bob at the end.

'Not sure the 8 lb weight is sufficient to provide enough recoil.

When well running, a careful observation will reveal motion in the folding pendulum joints, the action of sufficient escapement recoil. That is to say, that the jointed pendulum bob tends to swing in a slight parabolic arc as if the pendulum had Huygen's cycloidal cheeks.

 

[Scottie-TX]

Almost reads to me like the gaps - angles - of the pallet flags may be incorrect but before we jump off the deep end, are locks and drops equal, front to back of contrate wheel?. This will be a problem if contrate EW is not perfectly horizontal. I know pallets are fixed on verge staff but because of your problem, I'd remove verge staff and inspect them closely also. I'm thinking that if angle between them was too narrow, that locks would be shallow or absent.
Eight pounds I believe is typical - recommended for this movement. Mine ran eights.

 

[eskmill]

Scottie is right. (quote) This will be a problem if contrate EW is not perfectly horizontal. (unquote)

The front-to-rear location of lower escape wheel pivot (potence) on many Morbier movements is somewhat adjustable. Usually the upper pivot hole plate is usually not adjustable.

Make certain that the verge arbor and escape wheel both run in the same plane. That's easy to say but because the verge arbor has a cut-out to clear the escape wheel arbor, it is difficult to evaluate. Too, wear of the pallet faces can be a problem.

Don't expect lots of locking but do look for a generous recoil.

 

[MLSchlot]

Thanks to both of you for the tips. I can verify the correct folding pendulum is installed with the movement, and the pallet blades don't exhibit any wear. I can't tell if the pitch of the blades are correct or not, as I have no point of reference. However, I agree that other things need to be looked at first.

The turned post anchoring the bottom of the escape wheel arbor only offers a vertical adjustment via the brass pivot cap. The only way to adjust the horizontal plane of the crown wheel is to place shims under this post, moving the bottom pivot towards the rear. Or, I can shave some material off the brass bushing attached to the top of the case, which anchors the upper pivot of the escape arbor. That might give me a little more adjustment front and rear.

How much end-shake should I have in the escape arbor? Right now I have about 1/16", which seems like a lot to me. I also have to be careful of the escape arbor pinion. It's worn and tends to slip against the #3 wheel. That's what got me deeper into this mess to start with. I moved the escape wheel down on the arbor, and adjusted the brass end cap at the bottom of the arbor to get the #3 wheel off the worn area of the pinion.

 

[Scottie-TX]

Except as a meshing consideration, I wouldn't think endshake critical here, as gravity is pulling the wheel downward and pallet strokes are also downward, depriving wheel of any upward motion.

 

[Jeremy Woodoff]

This won't help you much, but I have a crown wheel Morbier that came with one of the fancy repousse pendulums and dial surrounds. I suspect they are not original, but the pendulum works just fine. I had to add some weight to the bottom, in the space between the brass front and steel back, to bring it to time. In order to increase the run time, since the clock is located above a radiator that prevents the weights from descending to the floor, I added pulleys. The strike side works using the typical 8lb weight (so it's working on 4lb). The time side wouldn't quite work on that, so I have a 12lb weight on that side. It's working fine on the resulting 6lb. There's very little recoil. I don't think I've ever had a clock more trouble-free than this Morbier.

Is it possible the joints of your pendulum are so loose that they are affecting the motion of the pendulum?

 

[Scottie-TX]

That is an INCREDIBLY good point you make!

Is it possible the joints of your pendulum are so loose that they are affecting the motion of the pendulum

I made my pendulum and learned quickly that any slop in the rod results in lost motion and stoppage. That is a GREAT place to look.

 

[laprade]

I enclose a picture of a folding morbier pendulum


bob weight 190 grams

diametre 6 1/4 ins 16 cms

the rivets on the rod are 1 cm in from the end.

the bob is hollow steel with an extra layer of brass on the façade.

is your clock a "gong" or "top bell" and does it have two piece pendulum suspension rod. I forgot to photo it.

The rod (32.5 cms) hangs inside a covered "sentry box" (?) on the rear of the top plate. 24 cms down a small loose riveted flat brass rod 5.5 cms goes over to bottom of the escapement crutch

hope this helps

 

[Tom Kloss]

...The rod (32.5 cms) hangs inside a covered "sentry box" (?) on the rear of the top plate. 24 cms down a small loose riveted flat brass rod 5.5 cms goes over to bottom of the escapement crutch...

Hi
Make sure that this connection point between the crutch an the pendulum rod does not have too much slop. Also, I would check the height of every tooth on the escape wheel. On my comtoise/morbier the height of the teeth varied as much as .028 between the lowest and the highest. I had to dress each tooth to equalize the height.

T.J. Kloss

 

[shutterbug]

How about a picture of the escapement? I don't think I've run into one of those

 

[Richard T.]

How about a picture of the escapement? I don't think I've run into one of those

This is not a good picture. I can't get to that side of the clock because there is a large wall clock on the left side and without taking it down I can't get a picture. Someone will probably have a better picture.

You can see the downward pointing "teeth" of the crown wheel.

Best,

Richard T.

 

[Scottie-TX]

Thanks for the picture, RICH. Thanks, because I recalled the wheel incorrectly as being toothside up. I still don't think endplay would be much a factor here in transferring power.

 

[Richard T.]

You're most welcome. I have seen other configurations of the crown wheel (verge) escapement but don't remember all the details.

Best,

Richard T.

 

[shutterbug]

Yeah, the picture is clear enough to see the EW, thanks! I can see that it's designed for lots of recoil, as was mentioned.

 

[Jeremy Woodoff]

The typical verge escapement does have a lot of recoil. But Morbiers have seconds pendulums, or nearly, and a typical verge escapement with a pendulum of this length would require a huge pendulum swing and would certainly not be capable of being contained within a case. I think one of the unique characteristics of the Morbier verge is that it was designed to have a much smaller swing and consequently less recoil. In fact, the arc of pendulum motion and amount of recoil are very similar to a typical anchor escapement. I think if you compare the pallet shapes and angles of the Morbier with those of a typical verge you will see that they are very different.

 

[Mike Phelan]

To continue with what Jeremy says, the pallet angle on a Morbier is typically 20-50 degrees, for the reasons he points out.

A typical verge is more like 90 degrees, and the pendulum arc maybe half of that!

 

[laprade]

Acouple of years ago, when I was restoring a french fermette, we had to take down a temporary (100 years) mezzanine made from the hafts of an ox cart in the "Chais" (winemaking shed). On the platform I found two verge morbiers, one with cast decoration, one with pressed. The french owner of the property gave them to me.

I enclose some shots which I hope will help. (if you want full size pic files, email me) The one with the dial was blinded by the dial so the decoration is not well shown. but you can see it on another shot. I also post two of the back, flash and natural light. I took some shots of the alarum, but seem to have mislaid them!

The strange sewing-thimble shape is the hammer counter weight.

I hope these help. If anyone wants fullsize pic files, email me, no problem.

laprade

 

[laprade]

I have found the alarum picture.