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1945: the 22A

22A - 18 jewels / subdial seconds at 6:00
22AS - 18 jewels / center sweep seconds

18,000 bph / 36 hour power reserve
28.8 mm diameter x 5.65 mm height

balance wheel:
monometallic with weighted screws on perimeter
8.4 mm diameter
Shock-Resist shock protection

adjustment screw near rotor pivot to compensate for wear

Research on this started in 1944 which made Longines a late comer in the automatic caliber game. The equipment had to be made to produce the parts. However, funding was very short at the time and their account for tools was dry by the end of 1945. Longines saw the mistakes made with self-winding ebauches by companies like Omega which sped their learning curve. They wanted to produce a bi-directional winding system that had become more sought after by the consumer of the time, but needed to consider variables like the winding efficiency and isochronism issues caused by the spinning rotor. Finally, 6 prototypes were given to employees of different departments for stringent testing, and in April 1946 the 22A was first available to the public.

1952: the 19A

19A - 17 jewels / subdial seconds at 6:00
19AS - 18 jewels / indirect center sweep seconds (driven by an additional wheel in the train)
added in 1954:
19AD - 19 jewels / subdial seconds at 6:00 + date
19ASD - 19 jewels / indirect center sweep seconds (driven by an additional wheel in the train) + date

18,000 bph / 36 - 39 hour power reserve
25.3 mm diameter x 5.05 mm height (19A) / 25.3 mm diameter x 6.0 mm height (19AS & 19AD) / 25.3 mm diameter x 6.95 mm height (19AS)

balance wheel:
monometallic with weighted screws on perimeter
8.4 mm diameter
Incabloc shock protection

Based on the manual wind caliber 8.68N from the 1930's, Longines used an excenter winding apparatus similar to the pellaton system employed by IWC to create the 19A. This was a much more refined and better decorated (all the bridges were rhodium plated) movement than the predecessor, but you can see some similarities to the 22A. It made sense to take a proven existing caliber from Longines' stable and modify it rather than start from scratch. Longines did not consider the automatic 22A a success since the manual version 22L was much better received and their management was suspicious of the durability and efficiency of the self-winding technology. Also, automatics were beyond the scope of many watchmaker's abilities at the time since they were relatively new. This factored into the decision to use this particular winding system since it was simpler and more robust than the 22A's set up.

1958: the 290

* all were produced with direct center sweep seconds - the 3rd wheel drives the cannon pinion
290 - 24 jewels
291 - 24 jewels / date @ 3:00 or 12:00
292/3/4 - 24 jewels / date @ 12:00 + power reserve indicator in the center of the dial driven by the hour wheel

19,800 bph / 45 - 48 hour power reserve
26.0 mm diameter x 6.0 mm height

balance wheel:
ring with weighted screws on perimeter
10.5 mm diameter
Incabloc shock protection

adjustment screw near the winding rotor's pivot

With another war going on, the economy had slowed and Longines was looking to cut back on costs. During this time they developed more derivatives off one base movement instead of many different movements in an attempt to standardize & streamline their production. Longines was also aware that many other brands were making a wealth of profit from less expensive, but still precise, movements. The 290 series was born of this turn in thinking, and you can see it is much less decorated than the 19A series. They still compensated for wear & imbalance of the rotor with a center screw adjustment like on the 22A. However, this series showed that Longines was still increasing the efficiency of the winding mechanism. The automatic system's gears were made from beryllium bronze (like a Glucydur balance wheel). Instead of the usual 60 small-tooth ratchet wheel, two 15 large-tooth pawl wheels with hook levers were used. No springs were required, which alleviated any pressure on the system which increased the lifespan and operation efficiency. The 290 series is more robust & durable than many other manufacturer's ebauches of the day or even any automatic Longines had created to this point. You'll notice that the rotor's perimeter weight was made slimmer - this made much more space available for the rest of the works at the heart of the movement, which provided room for larger components. Even though the 22A and 19A are measured as the total diameter of the movement, the "guts" are much smaller since the true diameter is several millimeters smaller than listed.

1960: the 340

* all were produced with direct center sweep seconds with twin 3rd wheels
340 - 17 jewels (1960)
341 - 17 jewels / date (1961)
342 - 17 jewels / variation to the milling of the gear train bridge (1963)
343 - 17 jewels / larger date than the 341 / variation to the milling of the gear train bridge (1963)
345 - 17 jewels / modified date mechanism (1965)

19,800 bph / 44 hour power reserve
27.0 mm diameter x 4.45 mm height (340 & 342) / 27.0 mm diameter x 4.6 mm height (341) / 27.0 mm diameter x 5.1 mm height (343 & 345)

balance wheel:
3 spoke glucydur with no screws
350 series = 10.34 mm diameter
Kif shock protection

eccentric rotor with ball bearings around pivot

This is the culmination of Longines lessons in building automatics. It combined a decent finish with great durability and accuracy. They finally figured a way around Eterna's patent on a ball bearing rotor which made a very efficient system. The only issue was the wear of the bearings - if they weren't kept in top shape the rotor could become off balance and scrape the caseback. The toothed circle is part of the rotor also and helped minimize wobble by keeping it on track. The balance wheel has an unusually large diameter compared to the overall movement size.

Longines realized that the average consumer worried more about the looks of the watch than what was inside it, so a priority was placed on making slimmer movements. The 350 series was an adaptation of the 340 that would offer a subdial second hand at 6:00 or no second hand at all, and also had more minor modifications done to the plates & bridges. The 350 without the date mechanism was 4.45 mm thick; the 351 with date was 4.85 mm thick; the 352 without date was 4.6 mm thick; and both the 353 and 355 with date were 5.1 mm thick.

1967: the 430

430 - 17 jewels / indirect center sweep seconds (driven by an additional wheel in the train)
431 - 17 - 25 jewels / indirect center sweep seconds + instantaneous date
432 - 17 jewels / no seconds
433 - 17 jewels / no seconds + instantaneous date

36,000 bph / 35 - 39 hour power reserve
25.6 mm diameter x 4.3 mm height (430 & 432) / 25.6 mm diameter x 4.8 mm height (431 & 433)

balance wheel:
3 spoke Glucydur
7.4 mm diameter
Kif shock protection

ball bearings around rotor pivot

Longines was not blind to the advent of electronic watches, and realized that higher beats per hour could theoretically achieve greater accuracy. There were drawbacks however - lubrication was one issue. Also, the physics involved with such a high rate and rotational mass caused them to reduce the size of the balance wheel, which reversed the trend in their automatic calibers up until this point. Most everything is covered HERE making any other additional comments to the 36K bph movement moot.

In 1972, Longines reduced the bph of their Ultra-Chron movements to 28,800 bph to help cure the inherent issues with the 36,000 bph calibers. Almost every part was identical to the 430 series except for a few modifications to some of the plates and the wheel train ratios. The 6641 had 25 jewels, and the otherwise identical 6642 had 17. The 6651 was either a 17 or 25 jewel movement but had the instant date mechanism added. The 6652 was 17 jewels, had the instant date mechanism, and was used in the Flagship HF (high frequency) series.
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