Hi all, I own an Aerosonic-LeCoultre 8 day aircraft clock ...



that's been working happily for 5 years up until now, after I've just had it serviced. Two problems have appeared:

1. The glass face, which is curved, was installed with the wrong side out. They're supposed to present a concave face but it now shows the convex [inner] surface on the outside. This did not fill me with confidence about the thought or experience that had gone into the work on the clock. It might be counter-intuitive to have a concave face but even to me there are some hints in the design that should show which way to put the thing in, even without experience or a manual.

2. Before I sent the clock off for a service, the sweep second hand would faithfully return to zero when re-set. now, it returns to a different point each time it's re-set, specifically 1/2 minute [60 minute scale on dial] further advanced each re-set. So, after 8 re-sets it's on the 4 minute mark.

On 1. the watchmaker reluctantly accepted that the glass was in back to front.

On 2, he suggested that the clock had been damaged in transit [yes, it was sent by mail, well packed]. I guess this is a possibility but I'm a little surprised that each re-set is 1/2 minute [clock scale] further around the dial than the one before, regardless of whether the clock is upright, on its back, tilted so as to allow gravity to favour the hand to "fall" towards where it should be.

The watchmaker had agreed to rectify the problems but because of 1. I'm not sure if I should trust him on 2.

Might I ask you here, is the sweep hand re-set entirely consistent with a loose hand caused by damage in transit or are there any alternate explanations for the problem?

 

It's certainly a loose hand based on your description, but saying that happened in transit is a stretch to say the least...

 

Thanks Archer. Tossing the idea around in my head, it seemed likely that if the interference fit was strong enough to handle the stop start forces of "zeroing" [?] without slippage and for many repeats of the action, it should fairly easily handle any shocks short of something that would destroy at least the balance wheel pivots, or maybe the whole clock.

 

Could I ask a detail question here?

When you're pressing a second hand into position, how do you make sure that the fit is tight enough and can you tell by feel if it isn't going to hold?

 

Just to add a little detail here ... The clock/watch has the same hand on it before service as it had after service. Before servicing there was no problem with the fly-back operation. I suppose even careful removing-replacing hands is always going to cause wear needing replacement at some point but presumably the expertise comes with knowing where that point is?

 

Combination of the force required (feel) and the distance the hand goes on. It’s also good practice to test the start/stop/reset several times after fitting the hand to make sure it doesn’t move.

If the hand is loose they can be tightened typically, unless the pipe is split. In that case you either need a new hand or have to replace the split pipe, which can be more involved...

 

Thanks, that's very clear and helps me understand whether what my watchmaker has been telling me is open and coherent or defensive of possible errors that should have been apparent, groan.

 

Good and bad outcome here. I removed the face of the clock to correct the glass problem ... relatively easy though the glass consists of two sandwiched lenses in the shape of wedges, one thick at the top, the other thick at the bottom with both being ground as lenses [sorry, really should have taken a photo, hard to describe but optics worthy of a camera]. Re-fitting the glass was easy enough after figuring out which of the 6 or so options was correct.

The hand was perching and wobbling on the end of its shaft [?] with less than 1mm engaged where the pipe was about 4mm long. The pipe had been crudely crimped about 2mm from the bottom end [away from the hand], so much so that it wasn't possible to install the hand on its shaft beyond 1mm. Brass was stripped off internally on the narrow diameter [tube looks quite oval from the end]. Clearly, it was a tacky shortcut.

After I'd laid all this out clearly to the watchmaker he refunded the full $750+ he'd charged, so I'm glad of that. Still, I really hate being duped and had it not been for the advice above, I might have accepted that it was understandable for a properly fitted hand to come loose in transit and left it at that. There's rather a big jump from just cleaning and oiling a watch to giving it a full evaluation and making appropriate mechanical repairs.