Setting teeth not fully engaging

[skridlov]

Please overlook my incorrect use of some terminology!

The little one button chrono (which I erroneously identified as a Cyma) has a problem in that the setting teeth (stem in setting position) do not fully engage and thus jump. When rotating the crown anti clockwise they engage much more fully than when clockwise. I am attaching two snaps to illustrate both positions. I can see that the lever bearing the two wheels that operate the winding and setting isn't being fully tensioned by the abutting lever which bears the stem locking screw end. I can't see any missing spring and it doesn't seem likely that this part could wear enough to give such a gross error.

I'd greatly appreciate some advice on possible solutions. I realise that the movement is pretty grubby (this area looked as if someone had emptied a can of 3-in-1 oil into it...) but I have someone who wants to buy it if I can just fix the setting problem.

Thanks, Roy

 

Edited May 26, 2017 by skridlov
Wrong snap inserted

[skridlov]

Here's the same with the stem in the winding position.

 

[wls1971]

This type off hand setting and winding arrangment uses a rocker bridge that in one postion engages the winding and in the other postion engages the hand setting the large bridge must be binding with wheel under neath this is why when you turn one way the teeth engage but turn in the oposite direction it disengages, if as you say this area is covered in old oil it may be providing enough friction to bind the two together. The bridge should pivot freely where the large screw is without binding with the wheel underneath, disassembeling this and cleaning and then reassembling maybe all it requires to clean of the old oil and let the wheel run free.

to test this quickley turn the crown one way then the other if there is any movement in the bridge as you do this its binding

 

[skridlov]

Thanks. 

I can see how it functions quite well - I've removed this bridge and mopped up the excess oil. When the stem's in the setting position the problem is that this bridge doesn't actually move far enough to fully engage the set, If I put a little pressure in the direction of engagement I can see the gears mesh fully. Once this pressure's off the cogs start to disengage - less so when turning the crown anti-clockwise. There seems to be no provision for adjustment - I'd have expected (in my ignorance) that there might be a spring to ensure full engagement however the spring bearing on the rocker tensions in the opposite direction. Cue head scratching...

Roy

[frenchie]

From your description, it almost sounds like something in on backwards, or broken. Do you have a picture with the bridge removed?

[rogart63]

That movement looks like the AS 922 i have? If you look at the spring that press on the rocker arm. Do you see the halfmoon shaped thing at the end? That is missing on your movement and spring. Could it be that it's broken? 

[wls1971]

 

That movement looks like the AS 922 i have? If you look at the spring that press on the rocker arm. Do you see the halfmoon shaped thing at the end? That is missing on your movement and spring. Could it be that it's broken? 

The half moon shaped thing on your A.S 922 looks like a later addition to me as the pictures I have of it do not have one fitted at the end of the spring this would provide extra tension on the rocker bar when its in the winding position  

Edited May 26, 2017 by wls1971

[rogart63]

 

The half moon shaped thing on your A.S 922 looks like a later addition to me as the pictures I have of it do not have one fitted at the end of the spring this would provide extra tension on the rocker bar when its in the winding position  

You mean that it was there from the beginning? That somebody has modified it? Could be? Could also be that the  one on the picture  is missing? 

If you look at a EB or Brac that has the same kind of rocker bar. They also have the half moon shaped end. 

Edited May 26, 2017 by rogart63

[rogart63]

Saw the other thread about the movement now. See that the movement is a AM . Maybe a 237. 

[wls1971]

 

You mean that it was there from the beginning? That somebody has modified it? Could be? Could also be that the  one on the picture  is missing? 

If you look at a EB or Brac that has the same kind of rocker bar. They also have the half moon shaped end. 

Well it probably is original then movements do have modification made by the manufacturer through their production runs, the 922 on the ranftt site shows the movement without a half moon shape on the tension spring.

[skridlov]

Thanks for the additional information even though I'm still unsure what's going on. What puzzles me is that this half-moon doodad would serve to increase the pressure in the wrong direction.

What appears to be happening is that when the stem is withdrawn it doesn't come out far enough to push the lever (whatever it's called) which tensions the rocker in the setting position sufficiently to fully engage the teeth. If I push the rocker manually a little more the teeth will engage perfectly - it's only a fraction of a mm. If you look at the cup shape at the setting end of the rocker when it's in position the small cog is distinctly off centre as the cupped recess is clearly meant to be roughly concentric with the cog.

The tension spring seems to do what's intended, pushing the rocker back into the winding position. Doesn't look damaged to me.

Anyway, as a rank amateur I'm pretty stymied. If I was an engineer with access to the tools I'd make a replacement rocker with half a mm extra at that end. But I'm not and I can't...

Anyone got an inspired solution?

Roy

[skridlov]

Snap of the rocker removed follows tomorrow. 

[skridlov]

Here are the additional pix.

 

Edited May 27, 2017 by skridlov

[skridlov]

There appears to be a lot of free play in the centre of the two smaller cogs.

[skridlov]

Another snap with the stem in the setting position.

 

[wls1971]

Just reassure me but I assume these pics where taken before any cleaning took place they are grossly over oiled you did say you mopped up excess oil on a earlier post, but this requires a full strip and clean nothing less.

[skridlov]

Yes, of course, it's exactly as it arrived and clearly needs a full service - it's filthy. However before deciding whether that's worthwhile I need to be reassured that there's nothing missing from the setting sub-system. If I can rectify that problem I may have a buyer for it as it is. I've gone for full professional service in the past only to discover additional (sometimes all but impossible to rectify) problems rendering the whole enterprise a net loss!

Everything else aside, this problem intrigues me. I'm obviously a novice at this but I've done a lot of fault-finding in all sorts of system and technologies in the past. I just can't see what the problem even might be. (Launches distress flare...)

Roy

[wls1971]

Let me assure you that any effort on that watch is going to be worthwhile, its a small sized military chronograph of the world war 2 period, collectors will want it, I would expend the effort strip clean and then try and assess the problem, this may seem like a waste of effort, if infact you cant sort out the problem in the end, but some times you have to be prepared to sit on things for a long time parts may turn up in the future, if indeed are needed.

I wouldnt even try to diagnose the problem until I was absolutley sure every part was spotless and by the way it looks totally complete to me.

[rogart63]

I don't understand either? If you have a buyer that would be prepared to buy the watch? He would have to buy it as is? Nothing is perfect in old watches? If he should have a perfect watch he will have to buy a fully serviced or a new watch? 

As for the rocker bar? I think a good clean and some new oil and grease could do the trick. They look okay and don't look as they are very worn in the pivots or wheels. 

If it was my watch and should check for the problem . I would take one part at a time. Check that the rocker arm moves as it should without binding or excessive wear. Without the wheels. Then check if the wheels move as the should. Check if the small wheels has the same size. Check that the screw doesn't bind the rocker bar  when it's fully tighten?  

[skridlov]

Just to be clear, someone wants to buy it "as is" with the proviso that the hand setting must work. The above points are duly noted but, not to contradict in any way, the rocker is free from binding. What's most apparent is that the lever which bears the stem locking screw, and which pushes against the rocker, doesn't seem to move far enough to hold the rocker firmly against the setting cog. A little additional pressure against the rocker mates the teeth correctly. This looks like an out of tolerance problem (somewhere) to this amateur.

On the matter of the "military" designation of the watch, which excites a feeding frenzy among collectors, I don't actually believe this back plate belongs to the watch. It is an accurate press fit but a tiny bit larger overall than the case body.Suspicious too that the dial is signed with a French brand "Le Bois & Co" and the inner back plate is engraved "Stainless Steel" rather than "Acier inoxydable". Obviously anything is possible...

Roy

[StuartBaker104]

Roy,

It's hard to tell from the photos but is the end of the setting lever worn away, or is the hole in the baseplate worn so it can move around? With the rocker bar removed you should be able to see if the set lever jumps securely into each of its two positions.

The rocker bar spring does look as the it should have a half moon on the end wich has broken off (close inspection of the end will tell you), however it looks like it will still work fine like this.

S

[skridlov]

Hi Stuart

The setting lever doesn't seem to be the problem as it snaps correctly into both positions although without taking it off I can't see if there's any undue wear. I'm inclined to think if it's not that, the stem may be incorrect. If the stem doesn't retract sufficiently this would account for the problem. I think...

Roy

[StuartBaker104]

If the set lever snaps into position then the stem is not the issue.

Really hard to tell without having a good look at it all. If you now can't sell it I will look after it for you :-)

[rogart63]

If you take the stem out? And push on the setting lever only. Will the lever be able to push it all the way. Wrong stem or wrong setting lever. There is a spring under there also. Is that okay? Remove the setting lever spring and see if that works then. 

[skridlov]

Hi again.

With the stem out, pushing the setting lever into the setting position still doesn't move the rocker far enough. The rocker still has sufficient play to be nudged a little further at which point the teeth engage correctly. The setting lever cannot be pushed further manually. I'm a little reluctant to dis-assemble any further...

Roy