THE JOURNAL

Swiss ETA2892 movement

Article ArchivePublished 2011-03-14

The original base movement of the 2892 had a relatively slow frequency of 18000 BPH, and the balance wheel diameter was also larger. When ETA increased the frequency to 28800 BPH, they needed a mainspring that was much stiffer than the original. This required improving the winding efficiency of the automatic system to counteract the resistance generated by the stiffer mainspring.Aibiaozu---National leading watch forum, luxury watch forum, watch forum watch media K2 ? 4 A" [: h/ R3 @. w
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Just as the above problem was solved, ETA faced a new challenge in improving winding efficiency because, in order to make the base movement more widely applicable, they reduced the size of the base movement from the original 28mm to 25.6mm, which is the difference between 2890 and 2982, while the thickness remained 3.6mm. However, this reduced the size of the balance wheel and the weight of the rotor. Once all problems were resolved, we saw the 2892/A2.Aibiaozu---National leading watch forum, luxury watch forum, watch forum watch media/ s% M1 N9 X& G. S, t% J0 K( d! z
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From a technical perspective, the final improvement to the automatic section was to reduce the bevel on the edge of the rotor to increase its weight. At the same time, jewel bearings were used to replace the pins on the automatic transmission wheels. The automatic transmission wheels are used to drive the automatic top wheel; originally pins were used, but now jewel bearings are used, while the jewel bearings above the automatic winding bridge are replaced with pins. The effect of this replacement is to reduce the friction coefficient of these gear trains. Omega (and GP) further improved winding efficiency by reducing the diameter of the ball bearing base plate.Watch brand, {9 k* g7 V0 U9 l
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Figure 1 shows a disassembled Bulgari watch, which contains a 2892 modified by GP. First, let's look at the power source—the mainspring. As a non-first-tier brand, its mainspring is strong enough to provide sufficient torque. Compared to the barrel, the size of the barrel arbor is smaller. Like most modern watches, this is to allow for a longer mainspring. It can be seen that the mainspring occupies 75% of the remaining space in the barrel, whereas older base movements usually only occupied 50%.

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Figure 2 shows the entire barrel. Like other gear trains, it uses micro-teeth (also known as ETA-type teeth). This special tooth profile invented by ETA is used on both the gear teeth and pinion teeth, which can minimise friction to improve the efficiency of the transmission system. Modern movements, regardless of which factory provides them, have begun to use this tooth profile.
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Anyone can perform a simple test: install a transmission system using the Epicycloidal tooth profile used in high-end watches, do not add lubricant to the wheel axles, and then push the top wheel with an oiler; then perform the same test on a ETA2892 or Rolex 3135. You can see that the transmission of the latter two is much smoother.www.iwatch365.net9 m1 n: S% W1 J% z4 j4 |5 Z
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Figure 3 shows the complete gear train and escapement. Nothing out of the ordinary, and the overall finish is good. Please note that the wheel rims are made of Glucydur alloy while the pinions are steel. Friction coefficients between different metals are lower than those between identical metals. All quartz watch gear trains (including high-end quartz watches) use brass due to the much smaller torque within quartz movements, rendering high-strength Glucydur alloy wheels unnecessary.- ]$ ]2 ]" s1 ~% D- f
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The mainplate and most bridges and cocks are made of brass. Many factories plate these with rhodium, firstly for aesthetic reasons and secondly for corrosion protection.

The image below shows the gear train and barrel bridge with the bridges removed. The brass-coloured wheel on the barrel is the ratchet wheel.

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The image below shows the gear train on the reverse side of the barrel bridge. The leftmost component is used for manual winding assistance, while the rightmost is the final wheel of the automatic system used to drive the ratchet wheel. The spring and smaller diameter steel wheel serve dual functions: working alongside the brass-coloured wheel to control engagement, while the remaining parts act as a clutch assembly. It forces engagement during manual winding and disengages freely during automatic winding. The rugby-ball-shaped pin allows for bidirectional free movement.BiaoBiaoZu --- China's leading watch and horology forum, fine watch forum, watch forum   watch network media0 K8 V+ b5 w9 o# l4 - Q; }4 D

Figure 7 shows the assembled barrel bridge, ready to cover the barrel

Figure 8 shows the entire base movement with the balance wheel removed./ K2 T9 a; G$ z/ u+ o* [8 k2 k

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Figure 9 shows the movement with the balance wheel fitted. The 9mm balance wheel is a perfect combination of weight and size. Both ETA 7750 and Rolex 3135 use a balance wheel of approximately 10mm. In ETA's entry-level range, the balance wheel is made of nickel. ETA's regulation system uses a central hairspring, allowing quick and convenient time adjustment by altering the gap between the inner and outer studs. However, this system also makes reinstalling the balance wheel more difficult. Eccentric screws are used for fine adjustment, but cannot correct errors exceeding 5 seconds. The ideal position for the eccentric screw is in the central position shown..BiaoBiaoZu --- China's leading watch and horology forum, fine watch forum, watch forum   watch network media; Y# h; V# _$ C: M
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Figure 10 shows the reverse side of the base movement (dial side) fitted with the setting and winding mechanism
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Figure 11 shows the complete reverse side of the base movement, ready for the dial to be fitted. The large brass-coloured wheel at the 11 o'clock position is the date driving wheel. The brass gear teeth exposed beneath the outer calendar steel wheel are the date-jumping teeth. This simple yet ingenious design has been replicated by many factories because it is straightforward, durable, and achieves instant date jumping without requiring additional components. At the same time, it is extremely safe, allowing the date to be adjusted in either engaged or disengaged states without damaging any components.

Figure 12 shows the automatic winding system. The second wheel from the right is the reversing wheel. By working in tandem with the middle wheel, bidirectional winding is achieved. The leftmost wheel is the automatic transmission wheel. You can clearly see that the original pin has been replaced by a jewelled bearing. It is mounted on the pin at the 12 o'clock position of the automatic winding bridge./ j( G) R2 k, G% |% h2 `$ C2 I5 J
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Figure 13 shows the complete automatic winding assembly, ready to be mounted directly onto the base movement. Through positive and negative weighting, the effects of gravity under various conditions can be clearly observed.
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Figure 14 shows the complete movement, ready for casing.

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So how does it perform in competitive comparisons? There are some movements that rival it in accuracy and durability, but in my humble opinion, none surpass it. Rolex 3035 and 3135 are on par with it, but are significantly more expensive and thicker. Patek Philippe movements are much better looking, but fall short in accuracy, let alone durability—though Patek Philippe movements are considerably slimmer, which is a disadvantage here. Jaeger-LeCoultre 889/2 matches it for accuracy, but similarly lacks durability due to being overly slim, mainly because the Jaeger-LeCoultre mainspring is rather fragile. A thoroughly conceived and rigorously executed complete design requires everything to be near perfection. I do not have extensive experience with Blancpain/Piguet movements, but judging by the few numbers I have handled, they too fall short in accuracy compared to a healthy 2892.

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Like all ETA base movements, 2824 underwent continuous refinement to reach the layout we are familiar with today. If you consult technical literature, you will find numerous derivative versions of this movement featuring different appearances and beat rates, ranging from 18000 vibrations per hour to ultra-high-frequency 36000 vibrations per hour..iwatch365.net6 b% a- @8 C+ {- O* W f
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The dimensions of 2824 are roughly the same as 2892. The diameter is 25.6 mm for both, but the overall thickness is slightly greater at 4.6 mm (2892 is 3.6mm). That may not sound like much, a mere 1mm. However, considering the small scale we are working with, 4.6 is nearly 28% thicker than 3.6. 4 j* z# h$ W$ {8 m3 Z6 N& u) m7 O

As you can see from the images, 2824 shares many similarities with 2892:
Larger gear train layout space
Larger balance wheel diameter
Smaller ball-bearing baseplate diameter for
The crown (winding stem appears more logical) and primary automatic wheel are mounted above the barrel bridge. U" e& f: v9 L9 V0 D% r% {
5) The automatic winding system features two reversing wheels+ P3 m9 [( ^+ A9 d) l: U: ?" a
6) The automatic winding system is mounted onto the movement (2892 is installed on the back of the oscillating weight)

Why are both favoured by watch companies

In general, installing the automatic winding section within the base movement and placing the crown and automatic driving wheel beneath the barrel bridge can reduce the thickness of the base movement. The gear train layout of both is similar, meaning the centre wheel, third wheel, and second wheel (often referred to as the fourth wheel) are basically in a straight line, with the escape wheel slightly to the side. Both use the third wheel to drive the motion works. Most importantly, both can be fitted with additional functional modules and complications, and the mainspring torque of both is sufficient to drive these components without affecting the amplitude., b3 E) P/ y. : ^$ S
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In fact, if the amplitude drops by 15 to 20 degrees after adding a module, that component requires maintenance. This is an issue for the user to consider, as many watchmakers will not service such components. They simply remove the module, clean and oil the movement, and then reinstall the module. Many major brands also do not service these components; they simply install a new movement and module, then send the old one back to Switzerland for refurbishment, which we can infer from the maintenance costs.

Why is this? Because many components, such as chronograph or perpetual calendar parts, are extremely complex and require a qualified technician to service. Additional modules are highly dependent on maintenance; otherwise, if not properly cared for, it can cause the amplitude to drop by as much as 200 degrees. Such a watch, no matter how outstanding the original base movement is, cannot keep accurate time on the customer's wrist.

Accuracy

The most important of many questions from watch enthusiasts: how does 2824 compare to 2892? Or more precisely, is 2824 capable of the same accuracy and durability as 2892?$ r7 _! @. d$ A" {7 p9 t+ n
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Please note that the following is only my personal opinion, based on the hundreds of movements I have repaired or handled.
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If both use chronometer-grade parts and have been carefully cleaned, oiled, and precisely adjusted, what is the difference in accuracy? Of course, 2824 uses fewer of the aforementioned grade parts, so as the little brother of 2892, its reputation is not as high as 2892.

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In terms of durability, both are on par. However, I personally believe 2892 has a slight edge for long-term wear. This is because a larger ball-bearing base plate provides better support and better shock protection for the oscillating weight. Additionally, since 2824 has long been ETA's budget series and has only recently been offered to the high-end market, there is a gap in the investment and level of improvement compared to 2892. It is evident that compared to the Eterna prototype, the automatic winding section seems to have undergone few changes, and this part appears more prone to wear than others. . g) O5 C( G1 O* o; V4 x. p% e
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