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Swap your CHS movement to ICHS - Is it possible?

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    Swap your CHS movement to ICHS - Is it possible?

    This project started out as another attempted investigation into whether or not the rep Rolex GMT CHS movement could be repaired once the hour jumping spring has broken. That investigation is still on-going but as a corollary to it, I was also interested in seeing if the rep CHS cases would take either of the common ICHS movements, the 2836 ICHS or the DG2813/3804 ICHS movements (hereafter simply referred to as ‘3804’). For those interested in following the repair efforts, please see this thread:

    https://forum.replica-watch.info/for...-failing/page7

    Surely someone has discovered this before, but it was news to me and I haven’t seen it posted elsewhere so guess what? BOTH the 2836 and the 3804 GMT ICHS movements fit and function properly in the CHS case I had to work with. No mods to the case, rotor or caseback are needed.

    At this point I’d like to thank OldNavitimer whose posts I had seen indicating multiple CHS movement issues. I contacted him and he generously sent me three watches, a 2824 CHS, a 2386 ICHS and a DG2813 ICHS. Without his pieces to work on, I could not have made these tests and conclusions. Thanks bro!

    Both the ETA watches were BP factory, but I think it’s safe to assume we can apply the same results to other factory watches. Please post back with your own findings on other factory watches!

    I started off by taking some key measurements and doing some visual comparisons of the ETA ICHS vs CHS. Here is what I found. All measurements are in mm
    _
    2836 ICHS 2824 CHS
    Max dial diameter 28.0 28.2
    Rehaut aperture 26.8 26.8
    Distance from bottom of rehaut to center tube 3.9 3.95
    Distance from bottom of rehaut to underside of crystal 2.8 2.8
    Movement holder outside diameter 28.2 29.2
    Movement stem height 2.25 1.8
    Dial thickness 0.5 0.5
    Dial spacer 1.0 1.5
    Datewheel tooth ring height 0.75 0.9
    Hands H/M/S (GMT) 1.5/1.0/.25 (2.0) 2.0/1.0/.25 (1.5)
    `
    I did not see a need to measure everything about the 3804 case, but it’s stem height is 2.5mm and its dial spacer was .67mm, dial thickness 0.5mm

    So you can see the important elements of the two ETA cases are similar enough to be negligible, and adding up the stem height of the movement, dial, and dial spacers we get:

    2824 CHS: 3.80mm
    2836 ICHS: 3.75mm
    3804 ICHS: 3.67mm

    After reviewing the measurements and examining the cases, it’s apparent that BP just used a 2836 case to house the 2824 CHS movement. They used a thicker dial spacer to make up the height difference, and raised up the datewheel to help offset overmagnified dates. The extra space created by the thicker dial spacer on the 2824 CHS allows room for the modified intermediate date wheel, which we will see a photo of later. This modified intermediate wheel is considerably taller than its 2836 counterpart, and would have made using a 2836 as a base impractical.

    Here are some shots of the cases, crowns, dials, datewheels and dial spacers.










    Datewheels and dial spacers



    As ingenious as the design of the 2824 CHS is, I am struck by how cheap the parts are. It is a real shame that the time and money spent on pretty decorations and engravings for the backside bridges wasn’t better allocated to the movement parts that matter. The CHS movement looks marvelous when you open the back. Take the dial off and it’s a different story altogether.

    Here’s a shot of the two movements together. You can see in this pic that the CHS date corrector is missing. The hole for it to fit into the CHS movement is not a slot like a normal 2824, meaning it can’t move to the right with the crown in position 2. This disables the quickset date feature usually provided by this gear.



    Here you can see an additional intermediate wheel was added to the CHS to allow the date corrector gear to interact with the GMT wheel. This is where the hour jumping spring comes into play, supposedly freezing the GMT wheel while jumping the hour wheel (in gold color).



    In the next few pics you can see the intermediate date wheels and how much taller the modified CHS one is. The gears are reversed vertically to drive the reversed wheels on the CHS, all necessary to have the GMT and hour hand positions swapped. The third tiny gear on these wheels is to power the datewheel driving wheel to change the date.







    Here you can see just how little there really is to the CHS movement.



    Here’s pics of the 2 ICHS movements installed in the CHS case











    Things you will need to replace your CHS movement
    _
    Replacement ICHS What you need
    2836 ICHS CHS case crown
    CHS case movement holder
    CHS or ICHS dial
    ICHS datewheel with DWO (or CHS DWO cut off and swapped to 2836 DW)
    2836 ICHS Movement
    2836 ICHS dial spacer
    Hour and GMT hands (or whole new set)
    DG 2813/3804 ICHS CHS case crown
    CHS case movement holder
    CHS or ICHS dial (3804 dial must fit and have gen-spec date window position or CHS dial needs feet cut and redone)
    ICHS datewheel with DWO (or CHS DWO cut off and swapped to 3804 DW)
    3804 ICHS Movement
    3804 ICHS dial spacer
    Whole new hands set
    `
    This freshly serviced 2836 ICHS movement is happy in its new CHS case home.



    I hope this will be the first of many and we can start returning our paperweights to their former glory!

    A new DG3804 movement is about $40, hands about $20. Easily found on ebay or Startime.
    A new 2836 ICHS can be gotten for around $110, hands about $30. Look on ebay or ask your TD.
    Last edited by KJ2020; 26-09-19, 06:41.
    We are all related in time since time is relative to us all.
    GMT Movements Explained
    BP Rolex 16710 GMT Full Review VS Gen
    Swap your CHS movement to ICHS - possible?
    The Fantasy Watch Thread
    Noob GMT's poor bezel design
    Ceramic insert paint mod

    Double Nine Gonzo!


    #2
    KJ2020 Wow! Amazing write up that should be a sticky. I’m grateful to KJ2020 for doing this for all of us, and particularly for bringing my favourite Batman back to life! Thank you!!

    Comment


      #3
      KJ DID IT AGAIN!!!!!!!


      Sent from my iPhone using RWI

      Comment


        #4
        Originally posted by OldNavitimer View Post
        KJ2020 Wow! Amazing write up that should be a sticky. I’m grateful to KJ2020 for doing this for all of us, and particularly for bringing my favourite Batman back to life! Thank you!!
        You're welcome bro. Thank you for the parts to work on, and the willingness to help us all benefit from some workaround. Now on to Part Deux - Can the CHS movement be resurrected from the dead and made to work in a not too diminished capacity? We shall see...
        Last edited by KJ2020; 26-09-19, 04:24.
        We are all related in time since time is relative to us all.
        GMT Movements Explained
        BP Rolex 16710 GMT Full Review VS Gen
        Swap your CHS movement to ICHS - possible?
        The Fantasy Watch Thread
        Noob GMT's poor bezel design
        Ceramic insert paint mod

        Double Nine Gonzo!

        Comment


          #5
          An expert at work, thank you for sharing this. Amazing!

          Comment


            #6
            Thank you for the detailed explanation! The photo work is wonderful

            Comment


              #7
              Wow bro, nice write up. Very good explanation. Your work amazes me. I saw tickleshoes do a quick write up on how to fix it too. Is there a fix to the correct hand stack movements per say to make it more reliable?
              Last edited by Vvvlllooo; 26-09-19, 09:02.

              Comment


                #8
                Good work KJ2020 bro!!

                Comment


                  #9
                  Thanks for posting mate. appreciate you sharing the info!
                  APP ROO: Blue Batons, White Themes, GPFC, GPRG, RB2 Plat, RB2 Ti, White & Blue Montoya, Trulli, Buemi, Schumi, LBJ, RG PO Mexico, Don Ramon, White & Brown Safari, Auto Tour 2010 & 2012, Ceramic, Ginza, Panda, Navy, Survivor, Volcano, RGRC PAM: 569, 508, 364, 382 Bronzo, Egiziano, 425, 187, IWC: ZF Chrono, Big Pilot PP, Portugieser, Rolex: Daytona Blue Arab, Plat, 2016 Ceramic + most Subs and GMTs

                  Comment


                    #10
                    Originally posted by Vvvlllooo View Post
                    Wow bro, nice write up. Very good explanation. Your work amazes me. I saw tickleshoes do a quick write up on how to fix it too. Is there a fix to the correct hand stack movements per say to make it more reliable?
                    Thanks bro. There is an outside chance the hour jumping spring could be made slightly thicker or stronger. Perhaps just bolstered at the weak points as merlix has attempted. This would restore full normal functionality. Photo credits to merlix.





                    Failing that, I believe there could be a another fix. It would necessitate adhering the upper and lower halves of the GMT wheel together which Tickleshoes did and it worked for a while then quit. This approach needs further investigation. It would lock the GMT and hour hands together but a GMT offset can be achieved if desired by manually setting the hands with the offset.

                    Also in this second scenario I believe there is a possibilty of restoring the quickset date feature. Once the hands are locked, there is no longer a need for either of the two intermediate wheels linking the date corrector to the GMT wheel. After their removal, the date corrector is free to resume its normal function. As I noted above, the date corrector gear does not sit in a slotted hole in the movement like it does on a normal 2824, so the movement plate would have to be filed to create the slot. This could be easily done, child's play compared to what Micasol did to his skeleton Daytona.

                    I'm hopeful I can do this, I just wish I had more parts. If anyone has a dead CHS movement they can contribute to this cause, please PM me!
                    Last edited by KJ2020; 26-09-19, 14:02.
                    We are all related in time since time is relative to us all.
                    GMT Movements Explained
                    BP Rolex 16710 GMT Full Review VS Gen
                    Swap your CHS movement to ICHS - possible?
                    The Fantasy Watch Thread
                    Noob GMT's poor bezel design
                    Ceramic insert paint mod

                    Double Nine Gonzo!

                    Comment


                      #11
                      Originally posted by KJ2020 View Post

                      Thanks bro. There is an outside chance the hour jumping spring could be made slightly thicker or stronger. Perhaps just bolstered at the weak points as merlix has attempted. This would retain full normal functionality. Photo credits to merlix.





                      Failing that, I believe there could be a another fix. It would necessitate adhering the upper and lower halves of the GMT wheel together which Tickleshoes did and it worked for a while then quit. This approach needs further investigation. It would lock the GMT and hour hands together but a GMT offset can be achieved if desired by manually setting the hands with the offset.

                      Also I believe there is a possibilty of restoring the quickset date feature. Once the hands are locked, there is no longer a need for either of the two intermediate wheels linking the date corrector to the GMT wheel. After their removal, the date corrector is free to resume its normal function. As I noted above, the date corrector gear does not sit in a slotted hole in the movement like it does on a normal 2824, so the movement plate would have to be filed to create the slot. This could be easily done, child's play compared to what Micasol did to his skeleton Daytona.

                      I'm hopeful I can do this, I just wish I had more parts. If anyone has a dead CHS movement they can contribute to this cause, please PM me!
                      wow very nice brother. wish i had a CHS lying around for you!!! Please share for anyone who would like to donate for this cause!!!

                      Comment


                        #12
                        With this CHS movement being out for so many years already one thinks why they haven't fixed the problem yet. Seems like they only need to reinforce or rework the part so it's not as fragile. Then again I'm just a pedestrian naive enough to trivialize such matters

                        Comment


                          #13
                          Will this swap applicable to the new Noob Pepsi which is CHS?

                          Comment


                            #14
                            You should sign up as a tech consultant to Noob and ARF and get them pay you .... just saying

                            Comment


                              #15
                              Originally posted by Rubberman View Post
                              Will this swap applicable to the new Noob Pepsi which is CHS?
                              Yes
                              We are all related in time since time is relative to us all.
                              GMT Movements Explained
                              BP Rolex 16710 GMT Full Review VS Gen
                              Swap your CHS movement to ICHS - possible?
                              The Fantasy Watch Thread
                              Noob GMT's poor bezel design
                              Ceramic insert paint mod

                              Double Nine Gonzo!

                              Comment

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