Chasing Seconds: Omega's Spirate System And The Hunt For Precision

Also, there's a Jolly Roger joke in here somewhere.

Omega’s launch of the new Speedmaster Super Racing was overshadowed (at least for some of us) by an innovation in the movement, which is not something that happens very often in the world of industrial scale watchmaking. The Super Racing’s caliber 9920 isn’t an entirely new movement – in fact, there is only one difference between it and the METAS certified caliber 9900 (and variants) – but it’s a big one. The 9920 uses a new regulation system for the silicon balance spring which is also, as far as I know, the first regulating system for silicon balance springs, which normally omit the standard regulator found in many mechanical watches with metal springs. Instead, the 9920 uses something Omega is calling the Spirate regulator (we can at this point, take the privateer jokes as read).

New breed: the Omega Speedmaster Super Racing.

The harmonic frequency of a spring is determined by a number of factors, including the height and thickness of the spring, and the elasticity of the material from which it’s made but once a spring is made and installed on a balance, the only way to increase or decrease its frequency is by altering the stiffness of the spring. A standard watch regulator consists of a moveable lever, which pivots on the same axis as the balance. There are two pins through which the outer end of the outermost coil of the balance spring passes, which act to limit the oscillations of the spring, and which determine the actual active length of the spring. Moving the regulator inward shortens the active length of the spring, which makes it stiffer and increases the rate; moving the regulator in the opposite direction has the opposite effect.

Standard two-pin regulator (upper left) in a pocket watch with cut, bimetallic temperature compensating balance.

Other than altering the active length of the balance spring, the only other way to change the rate of a watch is to adjust the rotational inertia of the balance. Balances with inertial weights on the rim, like Rolex’s Microstella screws or Patek’s Gyromax system, can be used to change the inertia of the balance. Traditionally makers of precision watches preferred, when possible, to use adjustable inertia weights and dispense with regulators, as the latter interfere with the natural oscillation of the spring (a watchmaker’s basic principle was and still is, to some extent, that the spring should be interfered with as little as possible). However, many high precision watches, including those which participated in the observatory precision competitions, as well as millions of certified chronometers, use both regulators and adjustable inertia weights. Omega, since its adoption of silicon for balance springs, has up until now omitted any sort of regulator.

Rolex caliber 3255: Parachrom Bleu balance spring, without regulator, and with Microstella find adjustment screws. As with the Patek Gyromax system, and the inertial screws used by Omega, the screws can be adjusted without disassembling the movement.

The Spirate system consists of a more or less standard silicon balance spring, whose outer coil is attached to a flexible element fixed to the balance bridge. This element has, extending from it, a single long curved silicon blade spring, with a moveable outer attachment point. The position of the outer attachment point is controlled by a snail cam (which Omega calls a “graduated tuner”). Changing the position of the outer attachment point in turn affects the stiffness of the balance spring proper, and the rate can be adjusted in increments as small as 1/10 of a second.

Spirate balance spring

The upshot of all this is a claimed precision, in the caliber 9920, of 0/+2 seconds per day. For comparison, the Rolex Superlative Chronometer rate is ±2 seconds per day; Omega’s METAS calibers have a standard of 0/+5 seconds per day; the COSC chronometer standard for mechanical watches is -4/+6 seconds per day. Grand Seiko’s 9SA5 Hi-Beat caliber has a precision rating of -3/+5 seconds per day.

This means that the 9920 offers the best precision of any mass produced movement today. Omega has said that it intends to launch the system in other watches as well. It’s worth remembering, by the way, that while the stated precision of the 9920 is excellent, this is not the first time a mechanical watch has offered a precision of 2 seconds per day or better. A Girard-Perregaux observatory tourbillon tested at the Neuchâtel observatory in 1889, between April 6th and May 16th, showed an average daily rate variation of 0.38 seconds per day. Much later, Girard-Perregaux’s Chronometer HF watches, made in the 1960s and which competed with the first tuning fork watches, like the Accutron, were guaranteed to be accurate to within one minute per month.

However, it’s also worth noting that in the first case, we’re talking about a very expertly hand-tuned and hand-made watch whose precision could not be reproduced on anything even remotely approaching an industrial scale and in the second case, we’re talking about a very small run of manually adjusted timepieces which, although series-produced, were not particularly scalable to industrial production either.

There are several open questions about the Spirate system – the major question is whether or not the system will be used at scale across much or most of Omega’s production. While the system adds additional components, including the studs for the balance spring and for the outer blade spring, as well as the snail cam and a handful of other parts, there doesn’t seem to be any reason, in principle, why the system couldn’t be used at scale – the most complex part is the balance spring itself, which is fabricated in one piece from a silicon wafer, and which should present no obstacles to wider production.

It’s natural at this point to compare the Omega Spirate’s precision to the Rolex Superlative Chronometer standard. Spirate is certainly more precise although the caveat is that so far, the system exists in one movement in one watch, although if Omega wanted to ramp up production it could certainly use the 9920 in any watch currently running a 9900 caliber – the two movements are identical except for the regulating system itself, and the balance and regulating assembly from the 9920 looks as if it could be a drop-in replacement for that in the 9900. The Spirate system adds height to the balance bridge but it sits in a cut-out in the bridge which already exists in the 9900 series calibers.

You can object, if you are a traditionalist, to the technical complexity of the system and the use of high-tech materials which require a very high-tech manufacturing process to make, but on the other hand, silicon fabrication is at this point a widespread and mature technology (especially in watchmaking) and it’s not as if the niobium-alloy Rolex Parachrom balance spring can be produced from steel wire by a watchmaker at his bench either. In fact, producing Nivarox-type balance springs to scale is an industrial process, as a matter of fact.

It’s a fascinating achievement if you are interesting in bleeding-edge chronometry – if you’re interested in exploring more, I’d recommend Velociphile’s posts on the subject on Instagram, for starters. The Spirate system adds another interesting layer to Omega’s particular approach to chronometry, along with the co-axial escapement – a small part that makes a big difference in keeping basic research in precision mechanical timekeeping alive and ticking.