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WATCHES OF THE MONTH

 

COMPARISON BETWEEN
ETA 2836-2 AND MIYOTA 8205 MOVEMENTS

In the last few years, partly due to ETA’s policy of restricting supply of finished automatic movements (with long periods of delivery time) and partly due to costs, Miyota automatic movements are to be found in an increasing number of watches.
And as more and more people are asking the question “ETA or MIYOTA” I thought it appropriate to present a thorough comparison of the two.
In other words, are we comparing "like with like", or are there fundamental differences between the two movements?

These are the two executions/versions of each movement:

Automatic with date Automatic with Day & Date
ETA 2824-2 ETA 2836-2
MIYOTA 8215 MIYOTA 8205

Below are the technical specifications for each movement, as stated by their corresponding manufacturer:

ETA 2824-2

ETA 2836-2
MIYOTA 8215

MIYOTA 8205
WINDING OF AUTOMATIC Bi-Directional One direction
RUNNING RESERVE (hours) 38 hrs 42 hrs
Vibrations Per Hour 28800 21600
Timing micro-adjustment regulator Yes No
Stop Lever (hacking function) Yes No
Jewels 25 21
Accuracy -12~+12 sec/day -20~+20 sec/day
Maximum Positional Difference Under 30 sec Under 50 sec

For ETA, these are the specs of the ”Standard” execution. There are two more executions: (i) the ”Elabore” and the (ii) ”Top”, the latter being finished to Chronometer standards.
No alternative higher grades are available for the MIYOTA movement.

Now, let's examine various aspects of the two movements a little more thoroughly:

(i) Second hand: The second-hand of the MIYOTA movement is driven by a sweep second pinion - whereas on the ETA movement it is driven by a wheel.
The MIYOTA sweep second is indirectly coupling with the previous wheel (so there is no maintaining force on it) resulting in jerky jumps of the seconds wheel in the vertical position on certain watches with long and/or heavy seconds hand. (There is a spring pressing on the sweep second so as to prevent these abnormal jumps, but it is of little use on this kind of watch).

(ii) Shock resistance: ETA movements are equipped with either Incabloc or Novodiac shock absorbing systems for the protection of the balance staff, whereas MIYOTA uses the shock absorbing system developed by Citizen (Citizen owns Miyota).
All these shock absorbing systems behave satisfactorily for vertical shocks, but Incabloc is the best for lateral ones.

(iii) Balance wheel: The alloy of the balance wheel on the MIYOTA movement is weaker and is more prone to bending due to shocks.

(iv) Timing: Due to the lack of a micro-regulation system on the balance bridge of MIYOTA movement, it is next to impossible to accurately adjust the timing in increments of a single second.
Also a 28800 VPH movement (ETA) is by definition more accurate and precise than a 21600 VPH (MIYOTA)

Conclusion: By now my opinion is quite obvious. The MIYOTA movement is a good automatic movement that can work for many years with acceptable timing, but, it is no match for the ETA movement. And it was not developed and manufactured as a Japanese answer to ETA but rather to fill a gap in the market demanding a reliable and inexpensive movement. Therefore, and always according to my opinion, any comparison between the two movements is invalid.

Andreas Phasoulides.

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