The Little Engine That Could: deemed accurate and reliable enough to be used as a base movement for many high-end manufacturers’ complications

roadwarrior

Grand Tyme Master
Founding Member
Joined
Jul 17, 2014
Messages
64,641
[h=1]An In-Depth Look at the ETA 2892[/h] [h=2]Watch Information and History[/h] [h=4][Hamilton] [Bulova] [Accutron] [Water Resistance] [ETA 2824] [ETA 2892][/h] [h=1]An In-Depth Look at the ETA 2892[/h] [h=3]The Little Engine That Could[/h]
Hans asked me a while ago to do a write up on the ETA 2892. Both because of its enormous popularity, and also the fact that it is deemed accurate and reliable enough to be used as a base movement for many high-end manufacturers’ complications.

There’s not much I can add to Walt Odets’ history and evolution of the movement itself, except to say that most changes and updates were done in order to improve the efficiency of the automatic winding.

The first problem arose because originally the basic movement beat at a leisurely 18,000 beats per hour (BPH) and had a fairly large diameter balance wheel. When ETA upgraded the movement by increasing the beat to 28,800 BPH, this required a much stronger mainspring than what was used previously. This required upgrading the automatic unit by improving it’s winding efficiency in order to deal with the extra resistance due to the stronger mainspring.

No sooner had the above problem been adequately dealt with, when ETA gave themselves more winding efficiency headaches by reducing the diameter of the movement from 28mm to 25.6mm so that it could be used in a wider range of cases. Hence the change in model number from 2890 to 2892. Thickness remained unchanged, measuring 3.6mm for both models. This had the effect of reducing both the diameter and mass of the oscillating weight. A problem that was finally put to rest with modifications that resulted in the latest model, 2892/A2.

For the more technically minded, the final modifications to the automatic winding was to reduce the chamfer around the circumference of the oscillating weight – thereby increasing it’s mass – and to switch the stud and the jewel, which supported the intermediate reduction wheel. This wheel, which drives the ratchet driving wheel, originally had a stud, but now has a jewel. The stud has now replaced the jewel in the upper part of the automatic winding bridge. This resulted in less winding friction due to this wheels much greater stability. Omega (and Girard Perregaux) have increased the winding efficiency further by reducing the diameter of the ball bearing support.

I have ‘dissected’ a Bulgari labeled Girard Perregaux modified 2892 for you. So let’s take a closer look at it starting with its source of power, the mainspring. While not being very high, this is quite a strong mainspring and provides the movement with a more than adequate supply of torque. The barrel arbor has a small diameter relative to the size of the barrel. This is in keeping with most modern movements that use fairly long mainsprings. This results in the mainspring taking up about 75% of the available space, as opposed to older movements whose mainsprings only utilized about 50% of it.

ETA-2892-Parts1.jpg

https://www.watchdoctor.biz/eta-289...tt5nuYBqfa_MscFlVCXF_ADtbv39mpI3E4CDahIAo71mU

So how does it compare to the competition? There are some movements that match it in terms of accuracy and reliability, but in my humble opinion, none exceed it. The Rolex 3035 and 3135 match it toe to toe. But they are a lot thicker and considerably more expensive too. The PPs, while being very pretty to look at, do not match it for accuracy and are more delicate as far as reliability is concerned. Of course they’re also slightly thinner, so that does put them at a disadvantage. The JLC 889/2 does match it for accuracy, but is also too delicate to give it any competition in the reliability department. The main reason for the latter is it’s very weak mainspring. The whole design, while being well thought out and superbly executed, relies too much on everything being just perfect. It is thrown out of wack far too easily when even minor things go out of adjustment. I don’t have too much experience on the Blancpain/Piguet movements. But from the few that have crossed my bench, they don’t seem to deliver the same accuracy that the 2892 has no trouble delivering. Let me know if I’ve left any of your favorite movements out, and I’ll gladly comment on them.
 
I used to be a little disinterested in the movement in my watch. Now that I have several with the ETA 2824 I will say that silky smooth sweep hand is intoxicating. I'm not a sucker for accuracy as I'm a puller but they stay spot on while I have them on. I'm entering "movement snob" territory but just as a lurker not a member....yet..... I've got some Miyotas that are silky....9015 and 9100 and they too fluff my pillows
 
Back
Top Bottom