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New and reviewed: Armin Strom Gravity Equal Force

by Peter Chong on November 22, 2019
Overview
Brand

Armin Strom Gravity Equal Force

Complication / Type of Watch

Automatic time only with Equal Force mechanism for isochronocity.

Recommended Retail Price

CHF 16,900 before taxes

Armin Strom releases a new collection – their System 78, wielding their tremendous power of conceptualizing and building their own movements in-house with interesting new improvements. The new Gravity Equal Force is the first in the collection, and features two key innovations. Details within.

We have been keen on the work of Armin Strom since we began looking closely at the company created by Claude Greisler and Serge Michel in 2009 from Mr Armin Strom. Their Resonance series have achieved a lot of fame and focus on the international scene, and with the new System 78 collection, they revamped their entry level watches with their own in-house movement. The movement features two significant improvements – the use of a patent pending Geneva Cross stopwork mechanism with a brilliant de-clutching system for automatic winding, and the revival of the “motor barrel”.

Armin Strom Gravity Equal Force

The first watch to be launched in this collection is a time only watch, featuring the two improvements. The watch is available for customization with their Configurator Tool, and four variants were shown in the Dubai Watch Week where the new collection was launched. One in a white dial dial over a blue background, a blue dial over a gilt background, a black dial over a silver background and a blue dial over a silver background.

Our review sample is the one with a white dial and blue background.

The case, dial and hands

The case is a classical round case, measuring 41mm in diameter and made in stainless steel. The bezel is rather thin, and from the front of the watch, the entire dial face seem to stretch across.

The bezel is highly polished, rounded and angled, sits on a case middle which is brushed. The lugs which are angular and strong looking. The case is new and quite Teutonic in feel. The pronounced chin on the older Armin Strom watches is now reduced, and only a vestigial reminder of its historical roots to Mr Strom himself.

The hour-minute dial is off center, and features a surface with concentric engraved rings. This entire dial is raised above the back plate which is blue PVD over a frosted finish in our sample. Depending on the angle of incidence of light, it may appear as dark or brilliant. Within this sub-dial, two concentric markings in mirror polish are used to segregate two rings. The outer one marked as minutes, with the inner one with Arabic numerals For the hours. A subsidiary seconds hand is placed at 8 o’clock. Three bridges are prominently displayed on the right side of the dial,

The hands, like the rest of the watch, are made in-house in Biel/Bienne, and are lancet shaped. The hour hand is a short, stubby affair, while the minute hand is long and elegant and features a pierced interior.

Legibility of the dial is excellent, and the display of the beautifully finished bridges with their jewels provide the rather beautiful engineering aesthetic. The bridges feature highly polished anglaged sides, and internal angles as they are pierced.

The movement: caliber ASB19

The movement is new an developed in-house by Claude Greisler and his team. The movement features an automatic winding mechanism with a power reserve of 72 hours. As mentioned it features two key innovations to improve chronometrie.

The Stop Works with De-clutch

The first of the two is the Stop Works with De-clutch. The concept of this mechanism is to provide a constant flow of torque to the wheel train. As the mainspring unwinds, it discharges power via a torque curve with a broad fairly constant middle and short but highly variable ends. The torque is strong when fully wound, and wanes as the mainspring discharges. This differential power affects the wheel train because the torque supplied to the escapement system is not constant.

Some common methods to reduce this differential power and an effort to provide constant torque to the wheel train is seen in devices such as the stackfreed, the fusée-and-chain and the remontoir. However the Armin Strom solution is to ensure that the extremes of the power curve are avoided – utilizing the spring only on the middle portion where it is capable of providing a relatively constant torque.

This is how the Armin Strom Constant Force with De-clutch works. A Geneva stopwork device is used to stop the barrel from unwinding completely, and from winding fully. This device is common in handwound watches, as on full wind, the number of turns required of the mainspring to go from zero wind to full wind is fixed. This allows the Geneva Stopworks to be designed with the correct number of arms/slots to clip both ends of this wind by blocking the barrel. But in an automatic watch, this solution presents its own problems. The Stopwork installed in the AS operates the same way as in the handwound movement in the low torque portion of the curve. It effectively prevents the mainspring from unwinding to the last portion. But in the high torque end, the mainspring never stops being wound by the moving rotor. When the mainspring is fully wound, it merely slips within the barrel. Thus in the automatic winding system if the stop work mechanism stops the barrel from winding after the desired state of wind is achieved, the rotor will attempt to supply the force to wind further, but is blocked from doing so. Armin Strom feels this is not good for the movement and designed a de-clutching mechanism, releasing the rotor from winding the mainspring after the desired state of wind is achieved, and engaging the rotor again in the reverse situation. . This Armin Strom innovation is subject to a Patent Pending.

In our discussion with Claude, the Armin Strom mainspring takes 12.5 revolution from lax to full. But the ASB19 only uses about 9 revolutions, which Claude determined is the number with good power. The barrel is blocked by the Stop Works before it runs down to 2, and above 10. The de-clutching system operates when the stopworks blocks the mainspring at 10, allowing the rotor to swing freely without winding the spring.

The Motor Barrel

The second innovation is far simpler. In a traditional design, the central arbor is supported by jewel bearings rotating inside the barrel to wind the mainspring. Once fully wound, the arbor remains fixed while the mainspring pushes the barrel housing and so driving the going train. In this fashion, the mainspring barrel is not able to rotate at the precision of the jewel bearing but on the bushing around the arbor, resulting in a higher friction and a less precise rotation. The Armin Strom motor barrel design reverses this, and winding is made via the outer teeth of the barrel, and when the mainspring is discharging during timekeeping operations, the barrel remains stationary, but the spring discharges thorough a (new) wheel attached to the arbor which then drives the going train. This wheel’s pinion is then able to be supported by jewels, ensuring that it is able to rotate precisely and smoothly.

It is perhaps interesting that the second innovation is not quite a new thing, as Claude re-discovered it while repairing an old American made pocket watch which uses this same mechanism. It was originally used to ensure that the mainspring did not break due to the high frictions of the bushings. But the system has since fell into disuse as modern mainsprings are much stronger and seldom break.

Concluding thoughts

In the flesh, so to speak, the Armin Strom Gravity Equal Force is very attractive. The wrist feel is very light, very open, as suggested by the very open dial design with exposed bridges. The blue on the background provides a nice punch, aesthetically. And the entire ensemble looks elegant, due in no small part to the reduced and more streamlined, elegant chin.

The package is well thought out, and very pleasing. The finishing is very good, with all haute horogerie elements being addressed very well – both in the case, dial, hands as well as in the movement.

We think as an entry level watch, the asking price of CHF 16,900 is eminently fair and reasonable. And represents excellent value for money – a nice aesthetic, with a beautiful face, coupled with a competently designed, exclusive in-house movement featuring two innovations finished to a very high level.

Armin Strom Gravity Equal Force Technical Specifications

Ref. ST19-GEF.90.AL.M.35

Indications: Hours, minutes, seconds, power reserve indicator

Movement: Armin Strom manufacture Caliber ASB19
Automatic winding with micro rotor, Geneva-drive equal force barrel, offset display with subdial seconds
Regulating system: Balance wheel with 4 regulating screws
Power reserve: Geneva stop-work limited to 72 hours
Dimensions: 35.52 mm x 11.67 mm
Frequency: 3,5 Hz (25,200 vph)
Finishing: Hand-finishing to the highest quality level
Jewels: 28
Number of components: 202

Case: Stainless steel
Sapphire crystal and case back with anti-reflective treatment
Diameter: 41 mm
Height: 12,65 mm

Water resistance: 3ATM

Dial: Offset with subdial

Hands: Manufactured by Armin Strom – stainless steel with hand finishing
Straps: Delivered with a genuine black alligator leather strap and stainless steel ardillon buckle. A stainless steel double-folding clasp is an option.
Price: CHF 16,900

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