This article is a draft. I will continue to work on it.
The first commercially marketed automatic wristwatches attributed to John Harwood (1894-1965), an English watch maker, manufactured in conjuction with A.Schild (AS), Blancpain and Fortis and was exhibited at the 1926 Basel Fair. This started a rush of invention, with all manner of automatic winding mechanisms, including the Rolls in 1930, the Wig-Wag in 1931, the Glycine in 1931, the Autowrist in 1931, Rolex Perpetual in 1931 (the first 306 degree rotor), the Frey Perpetual in 1932, the Mimomatic pumpwind in 1932, the Aster in 1933 and the Pierce in 1933. One can add to this well known list, Roamer in 1933.
One of the problems many companies faced after the Rolex patents in 1931 was how to avoid infringing on them. The automatic winding system patented by Roamer in May 1933 is reproduced below (from patent CH169396)
In this a large weight 5 is deflected from its sprung center 16 as the wrist is moved, and by doing so turns the toothed ratchet wheel 8. If the weight 5 is deflected to the left, the ratchet winds, and then the spring returns the weight 5 to the center. If the weight 5 is deflected to the right, then the ratchet slips, and on the return to the center via the spring, the ratchet winds the movement. Did it work? The relationship between the bias spring and the ratchet seems critical. As such, it probably did not work well, and in December 1933, Roamer filed a second patent (CH176821).
Here the asymmetric weight winds a similar ratchet mechanism, and the bias spring has been deleted. It is unknown if any of these designs were made, marketed or even existed outside of the drawings, although it would be reasonable to expect that prototypes certainly existed as there were several patents. I assume that this development effort was abandoned, as from around 1934/5 AS (1049) and perhaps a little later, Felsa (279) produced bumper movements available to any manufacturer. It is this Felsa 279 that appears in an early Roamer Automatic watch – this one dates between the late 1930s and 1942.
The next step in the evolution of the Automatic movements was the 1942 Felsa Bidynator, in which Felsa was the only manufacturer to succeed in circumventing the Rolex patent by introducing bidirectonal winding. This movement was also adopted by Roamer and used until the development of its first in-house automatic design first patented in 1948. The following watch contains the Felsa 690 and is inscribed 1949 (probably produced in 1948) – more on this watch here.
Roamer’s first full rotor automatic design the MST410/1 was patented (CH272613A) and very efficient, but prone to significant wear. In the following diagram of the 410/1 automatic mechanism, the rotor turns clockwise turning the attached gear 3. This causes gear 7 to rotate in an anti-clockwise direction, and locks to the lower gear 8 due to the ratchet pawl 17. This transfers clockwise motion to gear 9, and subsequently anti-clockwise motion to gear 6, which winds the mainspring. As the same time gear 7 was rotating anti-clockwise, the rotor was also imparting an anti-clockwise rotation to gear 4. In this case, the pawl 15 engages the ratchet 14 and the plain friction clutch slips meaning that gear 4 and the ratchet 14 are turning in opposite directions, this motion of gear 14 was transmitted to gear 5 via gear 6. Thus motion in an anti-clockwise direction is applied to gear 6 no matter which direction the rotor is turned. While very efficient, with minimal lost motion – there is considerable wear possible in the clutches and ratchets/pawls.
From a collector’s point of view though – the MST410 is a blast to wear on the wrist as it sounds like nothing else as it winds, the following is an early 1950s example of an MST 411.
Roamer’s second automatic design, the MST420 addressed this wear to a large extent, but was more conventional in design and somewhat less efficient. The 420 was not available with a date, and in the meantime while Roamer developed their own solution, they adapted the Felsa 4002/4007N movements and internally numbered them the MST 441 and 452. The Felsa calibres were finely finished by MST, in particular: balance assembly, barrel and (possibly) the rotor. During this period Roamer filed a number of calendar mechanism patents while they developed their own unique calendar mechanism.
The magnum opus, in terms of automatic movement design at Roamer was the third automatic design and first appeared in the MST436 in about 1963.