Inside an ST16 (lot's of images)
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  1. #1
    Member lysanderxiii's Avatar
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    Inside an ST16 (lot's of images)

    I have quite a few threads on the ST-16, but I can't recall one that goes into the insides of one. So here in a few pictures is the disassembly of an ST-16...

    Here is the basic side of the ST-19 we all see: (pardon the finger prints and dirt, this is my spare/parts movement, so it's not the cleanest thing.)



    Here we have removed the auto-wind bridge, we can now see the second hand pinion friction spring, the auto winding "magic fingers" have been moved to one side to afford a better view of the spring.



    Here is the underside of the auto-wind bridge showing the magic fingers and how they work.



    Here we have removed the 3/4 bridge exposing the inner workings of the movement. Items to note are the hack lever (the "V" shaped piece near the stem), which acts on the third wheel rather than the balance in most movements. (Sometimes hacking these movement shows particularities not seen in other designs, this is the reason.) Also, we now can see the third wheel engages both the fourth wheel and the second hand pinion.



    The third, fourth and escape wheels have been removed along with the second wheel bridge and balance assembly. Items to note are the adjustable banking on the pallet cock.



    Here is the dial side, with the date wheel and the cover plate removed so you can see the quick change arm and the all the dial side wheels.



    Parts: (l to r, t to b) Rotor; Rotor Screw; Transmission Wheel; Pawl Lever, with jewel; Auto Bridge Screws (2x); Auto Bridge



    Bridge Screws (3x); Second Hand Pinion Friction Spring; Second Hand Pinion Friction Spring Screw; Main Bridge with the Floating Winding Gear still attached; Fixed Winding Gear.



    Click; Barrel (Mainspring installed); Ratchet Wheel; Pallet Cock Screws; Pallet Cock; Pallet Fork.



    Escape Wheel; Second Hand Pinion; Hack Lever; Second Wheel Bridge Screws (2x); Balance Cock Screw; Fourth Wheel; Third Wheel; Second Wheel; Second Wheel Bridge; Balance Cock, with Balance Assembly; Cannon Pinion.


    Date Dial Guard Screws (3x); Date Dial Guard; Intermediate Date Wheel; Date Dial; Date Jumper Spring; Date Jumper; Hour Wheel; Date Corrector; Date Driving Wheel; Intermediate Setting Wheel; Minute Wheel.


    Mainplate (Stem; Clutch Wheel; Setting Lever; Setting Lever Spring and Yoke still installed)



    These movements are, design-wise superior to many older Swiss movement such as the AS1900 series, at least in my opinion. They are simple and robust, even if there is not much decoration or artistic arrangement of the bridges as there are in the Swiss stuff.

    And one last thing, although this and the Miyota 8215 share the same design for the second hand, you do not hear of "second hand stutter" on these as much as on the Miyota.
    Last edited by lysanderxiii; January 19th, 2009 at 20:53.

  2. #2
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    Re: Inside an ST16 (lot's of images)

    Hello,
    It is sure great to be able to see inside and look at a watch movement I might soon be getting. I have a Promotheus Ocean Diver on reserve to purchase as soon as they come available and do have my insecurites coming from my ignorance of Chinese movements/watches. Do you have a take on accuracy of the ST16 I am curious to talk with someone like you who really knows nuts and bolts, and would appreciate any info you might offer.

    thanks,
    Dan

  3. #3
    Member lysanderxiii's Avatar
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    Re: Inside an ST16 (lot's of images)

    These are capable of accuracy on par with the Standard grade ETA 2824 or Seiko 7S36. Unfortunately, most people using these movement don't regulate them very tightly (given the cost range they work in, it really isn't surprising), so like the Seiko7S36 people don't believe they are that accurate.

    They are a little harder to regulate to satisfaction, as there is no mirco-adjustment for the regulator. Of course, the same can be said of quite a few movements.

  4. #4
    CMW & Sales Moderator gigfy's Avatar
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    Re: Inside an ST16 (lot's of images)

    Thank you very much for the dissassembly of the ST16 !! The photos & detailed info is great!! Here is another post with another ST16 and a ZSH movement. We should start a sticky with all of these type posts!!

    Disassembly of ZSH & ST16 movements

    Cheers,
    gigfy

  5. #5
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    Re: Inside an ST16 (lot's of images)

    Here is my experience with an ST16 movement I have just received. Problems started to appear as soon as it started working.

    * 1 When setting time, movement hacks as expected but as soon as I set it seconds hand jumps like 4 seconds
    * 2 If I shake it, seconds hand just stops for a brief of time. After it starts working again it starts gaining time. In about 2 hours it is like 7 seconds faster (so in a day over a minute)


    I thought Seagull's ST16 was the best chinese 21 jewels movement around but after this experience ....

    Does this all happens to all ST16 movements or did I get a really ...... lemon? Should I try to exchange it or does this happen to all ST16 movements?

    Thanks for the assistance.

  6. #6
    Member W123's Avatar
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    Re: Inside an ST16 (lot's of images)

    Quote Originally Posted by rolexio View Post
    Here is my experience with an ST16 movement I have just received. Problems started to appear as soon as it started working.

    * 1 When setting time, movement hacks as expected but as soon as I set it seconds hand jumps like 4 seconds
    * 2 If I shake it, seconds hand just stops for a brief of time. After it starts working again it starts gaining time. In about 2 hours it is like 7 seconds faster (so in a day over a minute)


    I thought Seagull's ST16 was the best chinese 21 jewels movement around but after this experience ....

    Does this all happens to all ST16 movements or did I get a really ...... lemon? Should I try to exchange it or does this happen to all ST16 movements?

    Thanks for the assistance.
    I had the same second hand jumping experience with my Alpha with ST16.

    Also I have a Voow Submariner with a Miyota clone (that hacks) which also does the seconds hand jump thing for whatever reason.

  7. #7
    Member lysanderxiii's Avatar
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    Re: Inside an ST16 (lot's of images)

    Quote Originally Posted by rolexio View Post
    Here is my experience with an ST16 movement I have just received. Problems started to appear as soon as it started working.

    * 1 When setting time, movement hacks as expected but as soon as I set it seconds hand jumps like 4 seconds
    * 2 If I shake it, seconds hand just stops for a brief of time. After it starts working again it starts gaining time. In about 2 hours it is like 7 seconds faster (so in a day over a minute)


    I thought Seagull's ST16 was the best chinese 21 jewels movement around but after this experience ....

    Does this all happens to all ST16 movements or did I get a really ...... lemon? Should I try to exchange it or does this happen to all ST16 movements?

    Thanks for the assistance.
    Like I said earlier, at the price point most Chinese watches are sold at QA is not as tight as higher priced watches. Loose QA allows a higher percent of infant mortality, if the parent company is willing to accept this cost, in the form of a higher return rate, it may still be cheaper than a more rigorous quality program at the factory.

    When one goes on-line and buys a watch for a bargain, you have to realize that the low cost will be cause something is done cheaper than in an expensive watch. Just about all of the cheap watches I have bought over the years and opened up have had minor QA defeciencies, such as fingerprints on the movement or dust/lint in the movement. Over-sights such as these could lead to improperly running watches.

    The problems you describe do not sound to be design related, but of a quality nature. Might we inquire what brand watch we are talking about?

    If it were me I would return the watch and request a new one, or this one be repaired.

    Quote Originally Posted by W123 View Post
    I had the same second hand jumping experience with my Alpha with ST16.
    This is the result of the hack lever stopping the third wheel as opposed to the balance. There are two possible explanations for this phenomenon.

    1) Because the the gear train is stalled upstream of the balance, the balance will continue to swing and possibly unlock one of the pallet jewels but not swing far enough to lock the other one. When the hack lever is released, tension is returned the the gear train and the escape wheel will start to turn, the pallet may not be able to engage the first tooth on the escape wheel and allow the movement to jump ahead slightly.

    2) The arresting of the third wheel with the hack lever causes the second hand pinion gear to move out of contact with the third wheel, releasing the third wheel allows it to move forward and hit the second hand pinion with enough force to move it out of contact again. This is basically the same mechanism that causes the second hand stutter in the Miyota 8215.
    Last edited by lysanderxiii; November 29th, 2008 at 01:29.

  8. #8
    Member SquishyPanda's Avatar
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    Re: Inside an ST16 (lot's of images)

    Very informative post. I love seeing machines taken apart to see how they work :D And nice explanation of the second hand jump and stutter. I think it's these idiosyncrasies that give each mechanical watch movement its own "character." Yeah it's kind of annoying when you're trying to test for accuracy, but since neither of my ST16's cost more than $100, I don't complain too much. Both are accurate enough and I even dropped one on a tile floor with no ill effects.


  9. #9
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    Re: Inside an ST16 (lot's of images)

    Lysander, great beak down and analysis, thank you.
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  10. #10
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    Re: Inside an ST16 (lot's of images)

    Thanks for the photo journal; now I won't have to take pictures when I open up my ST16 to give it a proper cleaning and oiling

    I love these kinds of posts

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