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wtchgk

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Everything posted by wtchgk

  1. Is the reversing wheel of the A7750 interchangeable with the ETA 7750 reversing wheel? Appreciate any insight you may have?
  2. Peter's straps rival the gen straps. Excellent construction, fantastic grains.
  3. wtchgk

    Dead 3714

    Am looking for a dead 3714. Given what I have seen -- stripped screws, damaged bezels -- I am not interested in a watch that has ever been opened. Please pm me if you have one. Admins please advise if this is the wrong place for the post.
  4. I have straps from Peter and I had a strap from TWB. Peter's are far superior in quality.
  5. Here are a couple of straps http://www.rwg.cc/topic/146387-fs-straps-for-iwc-3714-portu-peterwatchacc-bob/ The strap from Peter.watchacc is among the best you'll be able to find.
  6. Nice to show your method. But, the direction of the brushing needs to be exactly in line with the north south axis in order to match the gen.
  7. Just like to share some quick iphone pics of the 201/A I built with a case that I modded/reshaped a little while ago. I want to acknowledge that I could not have done this without being able to stand on the shoulders of the masters in the forums.
  8. The metal to metal friction of gear 3 and gear 4 of the nine to six transfer gears stopped the watch. When these gears were removed the watch continued to work. I have since replaced the jewels of gears 2, 3, and 4 to eliminate all metal to metal friction. I am testing how much of an improvement this is. The main problems, however, remain, namely too much overall friction because of the size of the jewels and axis and because these gears can't hold normal watch lubricants.
  9. Everything I posted refers to the new and improved version with the additional jewels. Please see the details in my thread from earlier today.
  10. I just made a post on this topic http://www.rwg.cc/topic/145132-portuguese-seconds-at-six-some-facts/ I have not seen any credible data that answers your question. I have placed a 3714 on a winder after it was fully serviced and it stopped working after 3 months. Of course, this is just a random data point.
  11. I have posted this previously in another forum. It is well known that there are reliability problems with the seconds at six movement. Because the 3714 is very desirable, members are constantly asking for information to help them decide whether to buy or not to buy. Responses range from ‘don’t buy, this is a ticking time bomb’ to ‘the movement is fine when properly serviced’. It is the latter response that concerns me. If someone spends $200 to $250 on a service then there should be a reasonably clear metric like x thousands of hours of operation between services or some other proven data that permits a valid projection. Unfortunately, most of the optimistic responses have been either extremely vague or, worse, demonstrated downright ignorance of the facts about the movement. Below I shall provide details of how the design of parts of the seconds at six movement is substantially different from the design that is predominant, well understood, and proven in traditional watches, and, I’ll show the problems it introduces. Hopefully, this can serve as a basis for obtaining real data on how the problems can be mitigated. The seconds at six movement is roughly speaking a normal A7750 (or ETA7750) where the calendaring parts have been left off and replaced with parts that perform the transfer of the seconds from 9 to 6. The acceptable reliability of the A7750 portion of the movement has been pretty well established, exceptions not withstanding. Going forward I’ll just discuss how the 9 to 6 gear design is different from that in normal watches and point out the resulting problems. I'll use very rough figures that I believe are sufficient to demonstrate my points. Please refer to the pics below for clarification. A normal watch gear that makes one revolution per minute uses pivots of about .2 mm diameter that ride at the top and bottom in plates with jewels that have cups to hold lubricants by capillary action. Of the five gears in the transfer portion three gears revolve around a fixed axis. For one of those gears the axis is about 2 mm in diameter and it is about 1 mm for the other two. The height of the jewels is at least double that of a normal watch jewel. In addition, two of those gears at any one time ride on a ring on the plates that is about 4 mm in diameter and .1 mm wide. This is metal to metal friction. The only exception where this metal to metal friction is not occurring or minimal is the 90 degree position of the watch. Some rough calculations show that the surface area of the friction and therefore the force needed to move the wheels is about 30 times higher then the force that would be needed if traditional gear designs were used. This number accounts just for the contribution of the surface area to the friction. It does not account for the lack of the kind of lubrication found in a normal jewel bearing. The 7750 movement has sufficient force to move those wheels when the friction surfaces are clean and polished even without lubricant. Because the wheels have virtually no capacity to hold traditional watch lubricants, the friction surfaces deteriorate quickly thereby increasing the friction to a point where the watch stops. The one piece of data I have shows that this occurs after about 2000 hours or three months of continuous operation. I have no data on how much this varies. If no modifications are made to the movement, various treatments of the friction surfaces have been proposed. In this case the question becomes, can these treatments hold for at least 18000 hours in order to achieve the often claimed two years of operation between services? On to the pics. This pic shows the configuration of the transfer gears. Gears 1 and 2 are below the plate. Gear 1 is the original output at 9. Gear 2 uses the same design as gear 4. Gear 3 revolves about the hour wheel axis which is about 2 mm in diameter. The teethed edge of the gear touches the top plate which has been removed. Gear 5 is the new output at six. It rides in a normal jewel in the top plate and a metal bearing with an oil cup in the bottom plate. This pic shows the ring on the plate that gear 3 rides on. This is a pic of gear 4. Gear 3 is the same. Both gears revolve around a fixed axis that is about 1mm in diameter and both ride on one side on a ring on the plate that is similar to that for gear 3. Unfortunately this pic is overexposed. But it shows the ground up metal area that goes all around. In this pic the transfer plate has been removed and it shows the original output at 9 with its gear.
  12. So far the most specific concrete data I have seen regarding the operation and reliability of the rep Portuguese seconds at six movement were time grapher results before and after the movement was serviced. I wonder whether anyone has data like ‘time of continuous non-stop operation’ between service and failure. Out of curiosity I placed a 3714 after being fully serviced on a watchwinder whenever I was not wearing it. The winder was an Orbita and all the correct settings were used for the movement. The watch failed after three months. The problem was as expected with the transfer gears. After removing them the rest of the movement continued to operate perfectly. This obviously is just a random data point. Given the design of the transfer gears I imagine other results may vary quite a bit. Perhaps others have concrete data to share.
  13. You need to remove the bezel in order to swap the crystal. I don't think this is a good watch to practice on. Unless you have the skill, practice and the right tools there is a good chance that you will damage the bezel and/or the midcase. You may want to check with the EU watchsmiths.
  14. Got a little impatient while collecting all the parts for my 202/A project, so I built this intermediate version. I intentionally did not modify the minute hand and the cannon pinion as I will be using an ETA movement.
  15. I removed my original reply. I misread the question, sorry.
  16. AR was done by Pbdad. The strap is from Peter, he posts on the gen forums as peter.watchacc.
  17. Just want to share some before and after pics of recent upgrades.
  18. Just completed version 2.0. A while back I had posted my first version. Here is a pic of that. This is the new version. Specs are as follows: Jackson case, tube milled down, holes drilled for double screw bars WSO double screw bars Sapphire with no AR T48 spring loaded crown (discontinued, I think) Reshaped Torobravo CG Jacob caseback FGD dial and hands Orloff strap Am now looking at candidates for a better case. I do have a DSN NB case but I am also considering options for reshaping a case.
  19. The gen movement does not fit in the rep case without modifications. I already said that fitting a swiss movement with the 'seconds at six' mods does not seem to make much sense. However, some dealers offer this watch with a modded swiss movement.
  20. Fitting would involve transferring the 'seconds at six mods' from the rep to the ETA 7750. Am not sure that this would be a significant improvement over the rep movement. The 'seconds at six mods' are not engineered to the same standards as either the base ETA or Asian 7750.
  21. I don't know how to source a 3714 crystal with AR coating. But Pbdad and Vacc provide AR coating services in the US. Don't know wether chieftang still does. Uwe does AR coating in Europe.
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