Andrew sent us this Heuer Autavia, and it’s running way too fast – about 5 minutes per hour. Usually, this happens if the hairspring is too short, e.g. two windings stick together, or it’s touching somewhere…
First of all, I notice dirt on the hairspring. This watch was sold to Andrew by a dealer in the US as freshly serviced…Also, the hairspring is a bit deformed – see the last bit of the outermost coil towards the stud.
The worst of the weak points of this movement – the intermediate setting wheel wears the plate down, and will then start to slip. This happens when the clutch is too tight, so too much force is needed to set the movement. The damage to the plate under the microscope, with the intermediate wheel in place. This is all too common, and the reason why I don’t have a Buren 12 in my collection.The movement almost taken apart.
When putting the mainspring back in, I notice that the bridle has broken off the end – the mainspring will just slip in the barrel, without being able to build up a decent power reserve. These mainsprings aren’t available for love nor money, so I order a manual mainspring, and fit it with an adaptor bridle from manual to automatic.
The new manual mainspring fitted with an automatic adaptor bridle.I’m nowhere near being able to put this movement back together, though. I notice that both pivots have broken off the auto winder click – somebody had just “thrown” it into its place, without it being able to function at all. Nice job.
Time to fire up the lathe, and to turn a new pivot. Here it is pressed into the click. I still have to size the right end, which I have turned a bit too long just to be on the safe side.But my problems aren’t over yet – the click itself has a worn tip, and it won’t engage properly with the wheel, so it can still turn freely in both directions.I take the click out again, and re-shape the tip so it will stop the wheel properly.
Having put the movement back together, it’s looking good on the timegrapher, but it’s still 5 seconds per minute fast! Time for some serious head scratching. I can exclude the balance and hairspring from the troubleshooting, as the beat rate is correct for this movement (21,600 b.p.h.), and my timegrapher shows me -6s/day, not +5s/minute. So the problem has to be somewhere in the gear train.This movement doesn’t have a centre wheel that’s in the centre, but it’s off-side, with the clutch on the centre wheel, and an intermediate wheel that drives the cannon pinion, which isn’t a clutch. (intermediate wheel second from left, centre wheel third from the left). Time to count teeth! The best way to do this is to take a high-res photo, and to count the teeth on the screen. What I get is this: