Grand Seiko’s SBGA229 diver’s watch combines traditional mechanical watch making techniques with electronic timing accuracy. The Spring Drive technology developed by Seiko makes this possible, and the result is an authentic diving watch with a unique inner life. In this feature in the WatchTime archive and Olaf Köster’s original photos, we will thoroughly do it once.
Grand Seiko stands at the forefront of the Japanese watchmaking industry. A unique Spring Drive technology is considered to be the best product Seiko has ever produced. Therefore, it makes sense for this kind of innovation to join the Grand Seiko series, which originated in the 1960s and whose form follows function. The combination of mechanics and electronics seemed perfect, but it took several years to integrate Spring Drive technology into Seiko’s exclusive product line.
Seiko introduced the Spring Drive technology in 1999, but due to the lack of a sufficiently effective automatic winding system, the power reserve time was short, which initially prevented the brand from incorporating the technology into Grand Seiko. Several years of further development finally launched the 9R spring movement in 2004. Our test table is equipped with a 9R65 version, which shows the date and remaining power reserve.
Its automatic winding system relies on a magic lever: Seiko originally developed this ratchet winding system in 1959, which subsequently improved efficiency, simplified maintenance and extended durability. The power reserve has been extended from 48 hours for a manually wound movement to 72 hours for an automatic movement. The 9R65 movement is now the most widely used 9R Spring Drive movement among the Grand Seiko models. Its development is possible because Seiko has the necessary expertise in the mechanical and electronic fields.
Spring drive for high precision
The spring driver combines the traditional spring power of a mechanical movement with advanced electronic equipment that does not require batteries or any other external energy sources. The movement generates energy in a traditional way, making the watch completely independent of external power sources. The mainspring provides power at one end of the gear train.
The other end of the conventional escapement is replaced by a regulating system, which generates a small amount of electric charge to activate the quartz oscillator. Instead of the escape wheel, the sliding wheel rotates uniformly on the electromagnetic coil, thereby generating electric current, which is conducted to the integrated circuit (IC) and the quartz crystal. When the quartz vibrates at a constant frequency, the IC calculates the required electromagnetic pulse, which adjusts the rotation speed of the sliding wheel, thereby adjusting the movement speed. Unlike the escape wheel, the sliding wheel is not subject to mechanical intervention, so there is almost no loss of power due to friction.
Therefore, compared with the mechanical escapement, the accuracy of Spring Drive is much higher. The average deviation calculated by Seiko is 0.5 seconds per day, up to 15 seconds per month. The deviation we measured on the wrist every day was 0.1 second. After half a month, our test watch increased by 2 seconds.
Spring Drive uses quartz technology to adjust the operation of the mechanical movement, so as to obtain higher precision than pure mechanical movement. This accuracy is attributed to the Tri-synchro regulator system, which converts the mechanical energy of the clockwork into the current of the integrated circuit and the quartz crystal. While the crystal oscillates uniformly, the IC adjusts the speed of the Review copy watch by applying pulses to the sliding wheel.
The silent second hand indicates the second
The glide wheel rotates clockwise 28,800 times per hour. This speed corresponds to the number of half-vibrations per hour that modern mechanical movements complete every day. However, unlike the escape wheel, the sliding wheel does not stop and release repeatedly, so the second hand moves smoothly around the dial, rather than gradually. Of course, there is no typical ticking sound, but the silent sliding of the second hand makes the time display of Spring Drive unique.
When the second hand is short, a luminous point slides above the dial. During diving, the brightness and stable rotation of this point are particularly important because they ensure that the wearer’s watch is still running. The hour and minute hands are also equipped with Lumibrite, a luminous paint developed by Seiko. These hands can be clearly distinguished because everyone has their own unique shape. With multi-faceted luminous decals, they can provide the best clarity under all lighting conditions where Seiko’s dive watches are renowned.
Professional diving watch
According to the diver’s watch, the crown is strong, knurled, can be tightened, and can prevent side impacts. The crown is easy to operate in any situation. The unidirectional rotatable diver’s bezel is also easy to use. It snaps into place smoothly in half-minute increments, is marked and calibrated almost every minute, and is attached to the Zaratsu polished case specially made by Seiko Shinshu Popular Watch copy Studio. Here, by gently pressing each stainless steel shell on a rotating grinding disc, it is hand polished to a high gloss. The bezel is set with titanium carbide, which is a particularly hard and shatter-resistant titanium and carbon composite material. The ergonomic angle and notched edges of the diver’s bezel ensure a firm grip. Last but not least, the case has a pressure resistance of 20 bar and is tightly sealed by a huge screw back cover decorated with the Grand Seiko Lion emblem.
The deployment buckle with hinges on only one side is a technical highlight. In addition to the side button and safety bow used to open the closure, the buckle also integrates an extremely powerful extension mechanism. The wearer can easily unlock the safety device without opening the clasp, and can increase the length of the bracelet by more than three centimeters. The expansion process proceeds step by step through 14 lock points. Simply push the bracelet back to the clasp to shorten the bracelet again. Like the entire stainless steel bracelet, the clasp is very soft and feels very comfortable on the wrist.
Manufacturer: Seiko Epson, Japan Shiooji Shinshu Watch Studio
Reference number: SBGA229
Functions: hours, minutes, central seconds, date, power reserve display, unidirectional rotatable diver’s bezel
Movement: Calibre Seiko 9R65A based on Calibre 9R Spring Drive, 28,800 vph (sliding wheel), 32,768 Hz (quartz oscillator), 30 jewels, Diashock damping, fine-tuning with Tri-synchro regulator system, 72-hour power reserve , Diameter = 30.0 mm, height = 5.10 mm
Case: Hardened stainless steel, titanium carbide bezel on the top of the bezel, sapphire crystal, anti-reflective coating on the bottom side of the table, strong bottom cover, waterproof to 200 meters
Bracelet and clasp: Hardened stainless steel, push-button deployment clasp with safety and extension device
Scoring results (deviation in seconds per 24 hours):
Average rate: wearing test +0.1
Dimensions: diameter = 44.23 mm, height = 14.12 mm, weight = 204 grams
Variation: Titanium Model SBGA031