Cost - The 25 Jewel ETA 2824-2 Automatic Movement can be purchased from Ofrei (A large watch materials house) for about $78. It is employed in watches costing thousands including the Rolex Tudor Submariner. The 21 Jewel Miyota 8215 costs about $37 and is used in watches priced from $100 and up.
BPH - Beats per hour. ETA 2824-2 28,800 BPH or 8 beats per second (4 Hz) vs 21,600 or 6 beats per second (3 Hz) for the Miyota 8215. Most mechanical movements run at 18,000 BPH or 5 beats per second (2.5 Hz). Both movements have higher than average BPH a plus.
Accuracy is generally better on movements with higher BPH. The TimeZone has an excellent article on the subject.
Higher end watches employ movements with high beats per second. An easy way to judge movement quality without taking it out of the case is to watch how smoothly the second hand runs. Higher quality movements display a smoother running second hand.
Finish - The finish on the ETA is smoother and more polished than the Miyota. The ETA is available with gold plating as used by the Invica 9937. This does not affect the performance of the movement. Many and many could argue who’s going to look at the movement anyway? It’s is an esthetic issue.
Jewels – The ETA has 25 Jewels and the Miyota has 21 Jewels. Jewels, typically synthetic rubis are used in watch movements, not to add to their value, but to reduce friction and wear on moving parts. Lower end watches may have only 7 to 15 jewels. The standard for quality watches is 17 jewels or more. There is an upper end to the number of jewels necessary, typically, anything over 25 jewels for these types of automatic movements are just for decoration.
Power Reserve - Power reserve is the number of hours a movement will run when fully wound. Most mainsprings will power a watch for 30 hours or more. The ETA has about a 40 hour power reserve, the Miyota has a 45 hour reserve.
Winding Mechanism – Both watches employ a winding rotor that winds the mainspring with the movement of the wrist. The Miyota employs a ball bearing unidirectional winding rotor. The ETA utilizes a ball bearing rotor that winds in both directions. The ETA takes less wrist movement to wind the mainspring.
Second Hand Drive – The Miyota employs an indirect second hand drive and the ETA uses the newer direct second hand drive. The second hand on the Miyota may appear to stop for a moment with various wrist movements, but this does not affect accuracy.
Shock Resistance – The ETA uses Incabloc shock resistance, a method developed in the 1930’s to allow the end jewels on the balance staff to move or ‘float’ so the balance is not damaged when the watch is dropped or bumped. The Miyota uses its own proprietary shock resistance on the balance (Parashock).
Hacking – The ETA’s second hand stops when the stem is pulled for setting the time. A feature called hacking. Handy for synchronizing watches like in the war movies, or setting the watch with a standard clock like WWV. The second hand does not stop on the Miyota 8215 when setting the time.
Date set – Bot the ETA 2824-2 and the Miyota have the quick set date function.
Conclusion - Both movements have a track record of accuracy, dependability, and longevity. They are employed by several low, medium and high end makes. The ETA 2824-2 in my opinion is the better of the two. It is Swiss made and has been in service since 1982. With 25 verses 21 jewels, higher beats per minute, omni-directional winding mechanisim, and hacking feature, the 2824-2 comes out ahead.
Based on price, the Miyota 8215 by Citizen is a great value and would be a good choice in an everyday watch or weekend beater.
Doug Clark
17jewel.com
http://www.17jewel.com/two.html
