An Artifact of Innovation: The Hamilton/Buren Intramatic [5/21/01]
Archives September 11, 2003 admin
An Artifact of Innovation: The Hamilton/Buren IntramaticPart I by John Davis May 21, 2001
Hamilton (which became Hamilton International S.A. in 1968) kept producing fully assembled watches under the Buren name as one of their “economy” lines (alongside Huguenin (whom they purchased in 1959) and Vantage (purchased in 1962)). They kept Hans Kocher (Buren’s chief designer) on as the president of Buren Watch Company S.A. which they owned and operated until Hamilton was in turn purchased by SIHH (later called SMH, now the Swatch Group) in 1971 (a controlling interest was purchased at that point, all watchmaking assets were then completely turned over in 1974). Buren went into liquidation within months. Founded in 1873 by F. Suter, Buren’s first automatic movement (Cal. 525) released in 1945 showed a novel approach to automatic winding that was indicative of things to come. It used a pendulum winding mass recessed into the movement, resulting in a thinner automatic system than other movements of its time. It was a fragile and not particularly efficient system and could not compete with rotor winding systems, even as found in the early bumper automatics of other manufacturers. In 1952 Buren released their first full rotor automatic with bi-directional winding (Cal. 541). It featured a massive rotor surrounding a small (9 1/4-ligne) movement. The smaller movement was made more accurate by the state of the art Glucydur balance and Nivarox hairspring and in 1953 they created the Cal. 538, the smallest automatic calibre with power reserve indicator, a device to assure the public that this new fangled automatic winding stuff really worked.
It was the “Intramatic” movement that Buren modified in a joint venture with Breitling-Leonidas, Dubois-Depraz, Hamilton (who owned Buren at that time) and Heuer to create one of the world’s first automatic chronographs in 1969, the “Chronomatic“. The “Chronomatic” featured a Dubois-Depraz chronograph module (8510) attached to the backside of the movement, effectively hiding the micro-rotor entirely within the movement. The last automatic movement that Buren made was the Cal. 82, which utilized twin barrels on either side of the center wheel pinion and a large central rotor. It could run at 28,800 bph or 36,000 bph and experiments were made with a 43,200 bph escapement. It was quite thick for its time (at 6.2 mm) and consequently only two or three hundred watches were ever completed with the Cal. 82 movement. The remaining parts for approximately 100,000 more were sold to Comor in 1971. References:
Thanks are due to Tim C, jim b+ and Paul Delury for providing historical information from various sources.Images:
Copyright © John Davis 2001All Rights Reserved |
An Artifact of Innovation: The Hamilton/Buren IntramaticPart II by John Davis May 21, 2001
Many movements that I’ve seen from the 60s and 70s feature offset cannon pinions. While traditionally the second wheel is located in the center of the movement (and often called the “center” wheel), manufacturers found that a direct center seconds layout was sometimes facilitated by placing the cannon pinion outside of the center of the movement. By moving the second wheel out of the center, a flexibility in the gear train layout was realized that helped to create thinner, more complicated movements. An offset cannon pinion typically drives the minute wheel (of the motion works) and applies power directly to the intermediate wheels in the keyless works, which can be a source of drag and stoppage in neglected or over lubricated movements. A major disadvantage of an offset cannon pinion from a servicing standpoint is that if it needs to be tightened (lanterned), the entire power train must be disassembled to do so. Because the second wheel in the Intramatic is pivoted (on the bottom) in a bridge that secures the minute wheel and intermediate handsetting wheels, we must assemble this portion of the top plate before we can proceed with the power train. It does not seem incredibly smart to me to place the pivot in a moveable bridge (a little shift one way or the other would be a bad thing) but it does seem to work fine. You’ll notice the spirally skeletonized minute wheel. I’m not sure if this is supposed to give the minute wheel a bit of flexibility (this seems doubtful) but the cutout does facilitate oiling the third wheel pinion.
After assembling most of the motion works (the intermediate handsetting wheels, minute wheel and the associated bridge) we can turn the movement over and focus on the power train. A curious design feature of the Intramatic is that both the seconds and minutes are driven indirectly. A small center seconds pinion with it’s own bridge lies underneath the outermost sweep of the rotor and is driven by the third wheel directly (unlike the traditional indirect center seconds layout where an auxiliary third wheel is used). The center seconds pinion is tensioned slightly by a thin copper washer (very similar to a dial washer) to reduce the jerky motion sometimes exhibited by indirect seconds movements. A weakness of this design is that it allows for no flexibility in how much tension is being created by the washer. I suppose it could be removed and bent more or less to change the tension but this seems a bit troublesome once the movement has been fully assembled. The center seconds pinion is unjeweled on the mainplate but is thankfully jeweled on the topside where the washer’s tension is focused. The rest of the power train is appropriately compact and the wheels and pinions are functionally finished.
From here we turn our attention to the escapement. After assembling the other functioning portions of the watch, it’s a good idea to assemble the escapement and see if it runs before addressing any issues with the automatic system, motion works or calendar mechanisms (not to mention repeater or chronograph modules). In this way, any issues with the power train, barrel of escapement may be addressed without disassembling any additionally systems/complications. The Intramatic is particularly friendly in this regard though. One major advantage (during servicing at least) of the micro-rotor design is that all the related mechanisms on the top plate of the watch may be accessed without disassembling or removing others. In this case, the choice to address the escapement first was not only one of habit, but also intended to save the most interesting portion of the movement (the automatic system) for last.
Before we finally turn our attention to the automatic winding system, let’s address the keyless works (they look like this, notice the groovy shaped wire spring) and the motions works (sorry, no picture, I guess it was pretty boring). Of note is that the mainplate shows signs of a calendar mechanism that is not present in this model.
One of the most interesting (and more visually striking) elements of the automatic winding system is the floating (swimming, gliding, free) pinion between two huge jewels. This is a stubby little doughnut of a pinion that floats between two large solid jewels and performs the direction switching that allows the Intramatic to wind in both directions. I’ve sharpened up my crayons in an attempted to illustrate this action in these two drawings. The floating pinion bridge (6) with its large jewel is transparent so that the action of the pinion may be observed. The switching gears (2 and 3 in the drawing) are enmeshed and always rotate so that the lower gear is spinning clockwise and the upper gear is spinning counterclockwise. In fact, the click (5, in black) ensures that they cannot spin the other way. When the rotor (1) is spinning in a counterclockwise direction (as in the first drawing), the floating pinion (4) spins clockwise and is forced into contact with the upper switching gear which it propels in a counterclockwise direction. When the rotor is spinning clockwise, the floating pinion spins counterclockwise and is forced into contact with the lower switching gear which it propels in a clockwise direction. The upper switching gear’s pinion is enmeshed with a reduction gear, which in turn transmits the winding power in one direction only. For manufacturing simplicity both of the switching gears have an associated pinion but the pinion on the lower gear serves no function. I promise that next time I’ll try to use an animation to demonstrate instead.
I’d very much like to take a look at later implementations of the Intramatic and see how these issues might’ve been addressed differently (or not). I’d also like to take a look at one of the highly jeweled models, heck I’d like to own one I think. Micro-rotor movements are aesthetically much more pleasing to my eye and Buren can be proud to have been the first company to introduce them to the watch buying public. Despite the obstacles that had to be overcome, they succeeded in making a very thin, very accurate automatic movement by employing revolutionary mechanisms that functioned reasonably well in a variety of different levels of execution and elaboration. As a classy example of a turning point in the history of both Hamilton and automatic movements in general, a Buren powered Thin-O-Matic makes for an interesting, horologically significant addition to any watch collection. The movement for this article was kindly provided by Kent Lee. Thanks are due to Tim C. for sharing his experiences with this movement with me.
Copyright © John Davis 2001All Rights Reserved |