General-Purpose Movement Modification Encyclopedia Part 1

Exploring the secret to achieving both originality and cost-effectiveness

Originally, general-purpose movements were developed with the aim of reducing costs and increasing their popularity through rational design. Since the late 1980s, many suppliers, manufacturers, and independent watchmakers have competed to apply their wisdom to these general-purpose movements, adding various modifications. As a result, they have acquired unique characteristics that are hard to believe are typical of general-purpose movements. We will examine the know-how behind these modifications, which are the crystallization of this wisdom.

The classic ETA7750 continues to evolve through "modification"

The ETA 7750 has reigned as the standard for automatic chronographs for nearly 40 years. The original 7750 was merely an inexpensive movement designed to popularize automatic chronographs. However, its large size gave the movement the potential to evolve.

Caliber L688.2 / ETA Caliber A08.231

Longines Longines Column Wheel Chrono SS Classic
New for 2010. The movement is a column wheel A08.231, which is suitable for a classic design. This chronograph movement is an exclusive Longines caliber. Automatic winding. Stainless steel (diameter 39mm). Water resistant to 30m. 357,000 yen. For inquiries, please contact Swatch Group Japan Longines Division at 03-6254-7351.

First released in 2009. This is essentially a new movement based on the ETA7750. The work was undertaken by Frederic Piguet, a subsidiary of the Swatch Group. Not only was the control system changed, as symbolized by the adoption of a column wheel, but the watch is also notable for its modifications aimed at improving reliability. The baseplate, bridges, brake lever, 30-minute counter wheel, and various springs have all been completely redesigned. Automatic winding. Diameter 30mm, thickness 7.90mm. 27 jewels. 28,800 vph. Power reserve approximately 55 hours.

Cal.E/J8150

Eberhard Extrafort Grande Date Column Wheel
Graham and Eberhard have consistently favored La Joux-Perret movements. This model is equipped with the Cal. E/J 8150 (=LJP8150) with a big date and column wheel. When it was first released in 2004, it caused quite a stir. Automatic winding. Stainless steel (diameter 40mm). Water resistant to 3 bar. 735,000 yen. For inquiries about Diamond, please call 03-3831-0469.

This is a masterpiece of La Joux-Perret's 7750 modification. The movement is an LJP8144 with a 30-minute counter relocated to the 3 o'clock position and a column wheel. However, because the basic components of the 7750 remain intact, only 17 parts have been changed. It's an extremely clever design. First released in 2004. Automatic winding. Diameter 30mm, thickness 8.40mm. 28 jewels. 28,800 vph. Power reserve approximately 42 hours.

　The ETA7750, released in 1973, has become the standard for automatic chronographs and has been adopted by many manufacturers. Designer Edmond Caputo's intention was clear: to make the movement as large as possible. As a result, the rotor was enlarged, preventing a decline in winding efficiency despite the simple unidirectional winding mechanism. The larger size also made it possible to form each component in a straight line. This allowed for the use of pressed parts, significantly reducing manufacturing costs.

　However, the 7750, with its large 30mm diameter, was seen as an ideal material for modifications by various manufacturers. From the late 80s onwards, various manufacturers released masterpieces based on the 7750, the pinnacle of which was the LJP8150 by La Joux-Perret. This replaced the ETA7750's operating cam with a column wheel. Although the design was significantly different, the approach of utilizing existing parts meant that the changes were limited to just 17 parts.
　The modification of replacing the cam with a column wheel is the same, but the ETA A08-231, released last year, is even more interesting. For example, the LJP8150 shares the same baseplate and bridge as the 7750. However, the A08-231 has a new baseplate and bridge. ETA and Frederic Piguet have completely redesigned the 7750 chronograph, with the exception of the gear train, dial mechanism, and automatic winding.

　The large space that characterizes the ETA7750 was certainly intended to make chronographs cheaper, but the 7750's "large canvas" gave this movement unprecedented possibilities.

Cal.LJP8952

Caliber LJP8952-2's foudre-ante (1/8-second counter) mechanism. The wheel train is located on the dial side, from the dedicated foudre-ante barrel to the foudre-ante escapement star wheel, which is coaxial with the foudre-ante hand. The power driving the foudre-ante comes from the wheel train of this dedicated barrel, and the speed is regulated by the star wheel escapement, which is coaxial with the escape wheel on the case back. Additionally, when winding the regular wheel train barrel on the case back, the foudre-ante barrel is simultaneously wound by the foudre-ante ratchet wheel, which is coaxial with the barrel arbor.

Rattrapante mechanism. When the rattrapante button ① is pressed while the chronograph is running, the rattrapante column wheel ② rotates, and the rattrapante wheel stop lever ③ stops the rattrapante wheel ④. The rattrapante hand, which is coaxial with ④, stops, and only the chronograph second hand ⑤ continues to move. When ① is pressed again, ③ is lifted and ④ is released. Then, the rattrapante reset lever is pressed by the presser spring, returning the rattrapante heart cam to the hand position of ⑤ and resetting it.

　La Joux-Perret specializes in modifying the ETA7750. Among their works, the LJP8952, a rattrapante (split-seconds chronograph) with a foudroyante (1/8th of a second counter), stands out for its originality and complexity.

　The Foudroyante movement was originally created by the independent watchmaker François-Paul Journe. What makes this mechanism unique is that it has a dedicated barrel for the Foudroyante movement on the dial side, and power is drawn from this dedicated barrel, while speed is regulated by a Foudroyante escapement wheel located on the case back, coaxial with the escape wheel of the regular gear train, separating the power system and regulating system for the Foudroyante movement.

　In fact, Journe further refined this idea he used in modifying the 7750 and later applied it to his own chronograph, the Centigraph Souverain. In the Centigraph, the power system and regulating system for the 1/100th second counter are separated, but what differs from the modified 7750 is that instead of using two mainspring barrels, the power system and regulating system are separated from the top and bottom (barrel wheel and barrel axon) of a single huge mainspring barrel. The Jaeger-LeCoultre Duomètre Chronograph's Foudroyante also uses a very similar dual-system mechanism.

　The 7750 has been a canvas for modifications, with many different ideas being put to the test. This is likely due in large part to its ease of use, in addition to its track record as the standard chronograph for nearly 40 years. It has served as a gateway for skilled watchmakers and up-and-coming modifier manufacturers, accumulating wisdom over time, and has evolved to the point where it can later be fed back into high-end models.