Monday, October 16, 2006

The New Audemars Piguet Escapement

The New Audemars Piguet Escapement, or ApeScape as I like to call it, really looks like a genuine improvement rather than some of the "innovation for innovations sake" we've had lately.

Rather than using silicon to paper over the inadequacies of the lever escapement, create some Heath Robinson assemblage or pretend a detent escapement works in a wristwatch without some serious compromises, AP have actually evolved quite a clever device.

The key issues for me are:
  1. Efficiency comes from the direct acting single impulse (no lever twixt escape wheel and balance).
  2. Timekeeping should improve from the single impulse.
  3. The amount of sliding is 1/8th of that of a lever escapement - so no lube required at current beat rates.
  4. The shock system to disallow incorrect placement of the lever is effective and does not require high precision manufacture to function (compared to the accuracy required to manufacture Omega's coaxial well.)
  5. Like the detent, it self corrects for changes in balance wheel amplitude. If a shock or movement gives a large amplitude to the balance wheel, the following impulse is reduced slightly. If a shock or movement gives a lower amplitude to the balance wheel, the following impulse is increased slightly.
  6. The behaviour of this self correction can be tuned by controlling the inertia of the escape wheel, locking point and angle - easy to do in production.
  7. The double hairspring is a further improvement not a requirement.
  8. The overall height of the balance and escapement is the same as a conventional lever system.
  9. The system inertia is compatible with very high beats e.g. 36000 vph or 43200 vph unlike Omega's coaxial without material innovation.
  10. Silicon parts could yet be employed to take it even further.
AP (via Renaud & Papi) have already had an escapement under durability testing for several years now. Prototypes have been under field trials in that most aggressive of shocking environments; mountain biking. Tests indicate that the escapement is capable to stay within 1 s/d of its normal rate under rough mountain biking conditions. A normal lever could not achieve this.

The only remaining question mark is that of self starting. As a simple impulse device, it cannot be so and the model that I was lucky enough to play with could be stopped at the dead middle of its travel. It didn't take much to start it again though, but it would raise some new questions for how to do a hacking movement with this system.

I believe Daniels' Coaxial was partly compromised by his insistence that a watch should be self starting. Given the other benefits of the ApeScape, I think it's possible to live without that.

1 comment:

Jean-Jacques Subrenat said...

Hello Velociphile,
thanks for yet another technical review, crisp and clear.
I am in a period where fascination for accuracy in watches outweighs styling or other considerations, and have become more attentive to subjects you have treated more than once.
Regarding escape mechanisms, 2 improvements seem to me particularly worthy:
- the new AP system seems to exist only in the very exclusive Cabinet n° 5 watch. Do you know of this being used in any production watch at AP ?
- Daniels' co-axial equips the Omega Planet Ocean (e.g. Chronograph), and from what an owner reported recently, measured accuracy is of the order of 1 sec. per week, which is remarkable. But it's a massive watch.
Can you indicate some material I could read about these mechanisms, not in the abstract, but in actual production and daily usage?
Thank you for keeping such a consistent quality in your blog!
With best wishes,