Perplexed: Omega 601 with great rate but low amplitude

[patchwerk]

Hey guys. After ultrasonically cleaning/rinsing and assembling this Omega 601 movement in seemingly good condition I am getting great rate but amplitude of about 220 in horizontal positions. I have done the following:

pegged all jewel and non-jeweled  holes
polished train, pallet, and balance pivots
treated pallet and escape wheel with epilame
tried swapping the bottom and top balance incabloc jewels
oiled with moebious oils including the escapement (no oil on pallet pivots)
tried two mainsprings, an original Omega one and a GR equivalent.
checked the sweep second mechanism (removing the sweep second pinion only adds about 10 degrees of amplitude as expected but doesnt bring it up to desired levels)
polished barrel arbor and barrel interface (they spin freely)
checked for worn barrel bushing or wheels running not flat (all are fine)
demagnetized and checked the hairspring is free and flat
checked roller jewel and that balance spins freely without pallet fork.
 

I honestly dont know what else to try. I have stripped it and cleaned it a second time with same results. Beat error is low. There  are no banking pins to adjust. What else could it be ... something like worn escape wheel arms?. I have attached a video of it running.

 

Any ideas?

Thanks.

Edited June 17, 2020 by patchwerk

[Nucejoe]

Check the lock of pallet jewel on escape tooth, if heavy you have some ampltiute to recover there.

There is also about 10degrees amplitute lost in seconds arbour, run a piece of sewing thread inside the center tube and clean. oil both sides of pinion on seconds arbour. 

Check how hairspring behaves in the slot of regulator arm.

Check end shake on staff, fork arbour and escape arbour. Also side shakes and of barrel arbour. Good luck.

[watchweasol]

Hi In all that work did you change the mainspring.

373_Omega 601 New (3).pdf

[patchwerk]

Yes in my original post I mentioned I tried two new mainsprings an omega 1208 and a GR equivalent.

How does this lock look?

[watchweasol]

Hi   it looks ok to me but the escapement is a very exacting piece of engineering as the attached document will explain.

The Project Gutenberg eBook of An Analysis of the Lever Escapement, by H. R. Playtner..html

[Nucejoe]

 

Sorry you had reported good rate, so ignore my suspician of hairspring behaviour inside regulator slot.

I agree with watchweasol, neither can call the lock heavy.

I check endshakes on staff, fork and escape arbour.

 

 

[patchwerk]

What do you guys think about the condition of these faces?

[rodabod]

The depth of locking looks fine.

Going back to the simple stuff:

- with the pallets removed, will the balance wheel oscillate for a significant amount of time before coming to rest?

- does the train run really free without the pallets, perhaps to the extent that it recoils after coming to a stop?

Repeating what I’ve said before regarding these “later” Omega movements (well, later than most of the stuff which I work on) they run with a lower amount of torque and are more fussy when it comes to cleanliness of the jewel bearings. 

[patchwerk]

When I take the second pinion out the wheels do spin freely and recoil a bit. i get an amplitude closer to 235 in horizontal with the second pinion out. It makes sense to me that it is a "high" friction interaction between it and the center wheel. When I have it in I have to turn the crown the slightest amount to overcome that friction for the wheels to start turning. The tension spring is properly adjusted as well...

this is all to say that while I do plan on trying the trick with the string thread through the center wheel to get it cleaner for the second pinion...I do not see it as the main problem since I only get to 235 with the second pinion entirely out.

I can see your point about these movements being fussy because the pinions are tiny!

@rodabod given what you said about lower torque what do you consider acceptable amplitude for these movements? Its also frustrating because the rate is dead on and stable.

 

Should the faces of the escape wheel arms be more polished then what is seen in the pictures I posted?

Edited June 18, 2020 by patchwerk

[Nucejoe]

I don't see dirty center tube as the main source of problem either, just that you are obviously loosing ten degrees there.  Oil lower and upper sides of the seconds pinion, then there is the jewel or brass bushing underneath the tension spring and on the train bridge, to oil. Independently driven min wheel is always a pain.

Tension spring is just to hold seconds pinion up to engage it with the minute wheel but should not push the pinion against the upper jewel.

Are you sure seconds arbour is not bent? 

At this point I am not thinking of a single fault causing the drop in amplitude.

But these face of the escape teeth you show looks like it can use a good polish, have never polished one myself, how do you go about polishing escape teeth? 

Do you feel a sideshake on minute or seconds arbours? 

 

[rodabod]

@Nucejoe the centre-seconds tension spring is not just there to hold the pinion in position. It provides the necessary friction to reduce “slop” in the meshing of the pinion leaves of indirect-drive* seconds. 

It would be best to put that aspect to one side at the moment as the watch does not run well without it fitted anyway. 
 

@patchwerk you will still want to aim for a typical amplitude for the be at isochronism, ie, averaging around 270 degrees over its running time. However, you may find that the balance is so excellently poised on the watch that the positional variation is still acceptable at only 200 degrees. These movements have finer pivots as you say and overall require less torque. This allows the designer to provide less wear and longer running times. 
 

The “dog legs” of the escape wheel look ok from what I can see. You can still see the machining marks. 
 

Did you use a water-based soap in your ultrasonic cleaner? Occasionally they can leave a greasy film which is hard to detect, especially if the soap solution has been used previously. 
 

Presumably you selected the correct GR mainspring - the selection for the similar 500-series movements can be slightly confusing as different thicknesses are quoted. 

[Nucejoe]

Correct @rodabod the spring also reduces the slop.

@patchwerk have you checked endshake on staff, or just loosen up the cock screw  a turn or two to eliminate the possibility of end stone pushing on pivot. Do the same with fork bridge.