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--- seiko_8r28 [02.12.2022 20:38] – created - external edit 127.0.0.1
+++ seiko_8r28 [03.12.2022 14:17] (current) – [Variants] gerdlothar
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+====== Seiko 8R28 ======
+Calibre **8R28** is one of a family of [[column wheel]] [[chronograph]] movements from [[Seiko]]. Derived from the [[Seiko 6R15|6R family]], this **8R** family also includes the **8R39**.
+The **8R** chronograph family was introduced in [[2008]] to power Seiko's [[Seiko Velatura|Velatura]] 2-register [[chronograph]]s. It is closely related to the [[Seiko 6R15|6R20]], sharing that calibre's balance, winding, and works, and runs at the same 28,800 vph. The chronograph portion is a module added above the top plate. The 8R39 is identical in specification to the 8R28 but features a [[Spron]] 610 balance spring and [[Seiko 9S55|9S "Grand Seiko"]] escapement.
+One unique feature of the chronograph is a three-pointed hammer, allowing all three chronograph hands to instantly reset together. This operates on three separate [[vertical clutch]]es, as each chronograph hand is individually driven. The date also has an instant change mechanism.
+===== Variants =====
+^Movement ^Winding ^Hands ^Date ^Subdial ^Jewels ^Power reserve ^
+|8R28, 8R39 |Automatic |Hour, minute, chrono seconds |Date window |Small seconds, chrono hour, chrono minutes |34 |45 hours |
+===== Applications =====
+  * 8R28
+    * Ananta (SAEK, SRQ), Brightz Phoenix (SAGK, SDGZ), Sportura (SRQ)
+  * 8R39
+    * Ananta (SAEK, SRQ)
+  * 8R48
+    * Presage (SARK), Brightz (SDGZ)
+===== External links =====
+  * [[http://forums.timezone.com/index.php?t=tree&goto=3627073&rid=0|BASEL-Seiko Valatura new automatic chronograph and more]]
+  * [[http://www.watchtime.at/archive/wt_2009_04/WT_2009_04_084.pdf|Clutch Performer]]
+  * [[https://reference.grail-watch.com/family/seiko-8r/|Seiko 8R Family Reference]]
+<WRAP ud ud_mov>
+**Description:**
+  * [[Automatic]] movement
+  * [[Column-wheel]] [[Chronograph]]
+**Functions:**
+  * Hours, minutes, small seconds
+  * [[Automatic]] [[bidirectional]] winding
+  * [[Diashock]]
+  * Chrono function [[central seconds]], 30-minutes, 12-hours
+  * [[Vertical clutch]]
+  * Date wheel
+**Data:**
+  * 34 [[jewels]]
+  * 28,800 A/h
+  * [[Power reserve]] 45 hours
+**Production period:**
+  * [[2008]]-present
+</WRAP>
+{{tag>Movements Chronograph_movements Automatic_movements Automatic_chronograph_movements Seiko_calibres Column_wheel_chronograph_movements}}