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Hacking the Casio F-91W to Handle 1000 Psi
- tenpaiyomi 7y agoVery interesting. I'm intrigued to know if anybody with experience knows why there is a common recommendation of warming the mineral oil, versus room temperature which the author did.
- dvt 7y agoAuthor here. Would also love to know if any chemist/physicist knows the definitive answer to this :) Also: why do some watches purposefully leave an air bubble in the watch? Is this an aesthetic choice or is there any benefit/detriment to it?
- monochromatic 7y agoCould be to help drive out any dissolved gases.
- deleted 7y ago[deleted]
- jacobush 7y agoMaybe a de facto expansion reservoir?
- michelpp 7y agoNo experience here. But my guess is warming the oil makes it less viscous and thus easier for small air bubbles to escape.
- semi-extrinsic 7y agoTo be precise, warming makes the oil exponentially less viscous, so it can be a really pronounced effect by warming it 30 degrees (depending on the specific oil).
- lwhsiao 7y agoMy guess would be that in addition to the viscosity, it preemptively compensates for the thermal expansion of the oil, since on your wrist will likely be warmer than room temperature. Here is another detailed liquid-filled watch guide [0], which talks more about handling thermal expansion, where rather than using an air bubble, he opts for some sort of foam ring. Another person recommends Flourinert with foam rather than mineral oil [1]. [0]: https://www.christopherwardforum.com/viewtopic.php?f=5&t=4960 https://www.christopherwardforum.com/viewtopic.php?f=5&t=496... [1]: https://forums.watchuseek.com/f21/liquid-filled-citizen-654085.html https://forums.watchuseek.com/f21/liquid-filled-citizen-6540...
- LeoPanthera 7y agoI am frustrated that he didn't have a way to test it and so has no idea if it actually works.
- travisjungroth 7y agoI would bet it did. Here’s an F-91W hydro modded with olive oil taken to 3000 feet. https://forum.tz-uk.com/showthread.php?330958-The-Little-Watch-That-Could https://forum.tz-uk.com/showthread.php?330958-The-Little-Wat...
- synthmeat 7y agoI was just reading yesterday about another case too - https://forums.watchuseek.com/f2/my-oiled-casio-f-91-dives-deeper-than-40-meters-several-times-many-underwater-photos-3692106.html https://forums.watchuseek.com/f2/my-oiled-casio-f-91-dives-d...
- akavel 7y agoHe seems to mention purposefully creating an air bubble in the enclosure (by letting a few drops of the oil drip out) — why would he want to do that?? > "I slightly loosen two screws, to let out a couple of drops of oil (which would allow forming a bubble inside the box)."
- TheSpiceIsLife 7y agoIf the oil expands and contracts with temperature then the bubble would allow this without the oil blowing the seal. I think that’s the idea. Could be wrong.
- dvt 7y agoFair point, I'll take it out next time I go diving and report back!
- londons_explore 7y agoIf you live near an ocean, just tie the watch to the end of 700m of string, and start lowering it over the side of a boat. Pull it back again and see if it still works. Obviously you need a deep ocean, so check a map first.
- iammiles 7y agoLooks like a fun little project to do next weekend. Does anyone know where to get a strap like the one shown in the article?
- w-ll 7y agoIt's just a NATO strap. Very cheap and functional for people that don't like hard watch straps. It seams the color combo is Navy/Crimson/Ivory Found this on Amazon https://www.amazon.com/BARTON-Watch-Bands-Crimson-Standard/dp/B00ZO6GA8Q/ https://www.amazon.com/BARTON-Watch-Bands-Crimson-Standard/d...
- dingaling 7y ago> It's just a NATO strap Which ironically aren't a NATO standard, but a UK MoD spec.
- chrisseaton 7y agoI don't think these even are NATO straps - they don't fold back on themselves like the issue ones do, and these have an extra fabric flap that issued ones don't. This is a genuine 'NATO' issue strap: https://www.cwcwatch.com/collections/m-o-d-spec/products/cwc-nato-watch-strap-1 https://www.cwcwatch.com/collections/m-o-d-spec/products/cwc...
- Pinckney 7y agoLook for an 18mm Nato strap. It looks like Clockwork Synergy makes them with the nylon keeper, if that's important to you.
- ctack 7y agoI have one of these watches and really wanted, but decided not to mod it with such a strap as the metal buckles would potentially start to scratch my laptop.
- chrisseaton 7y agoThese straps are like ties - you get one in the colour of your school, university, club, or regiment.
- ComputerGuru 7y agoI don't know if I would even remotely trust that not to leak. The same watch is notorious for not having a quality seal and quickly fogs up in the shower. I would rather trade some meters and use straight up petroleum jelly injected into the casing at a high pressure; I'd be much more comfortable wearing that (and, yes, it is technically a liquid even at "freezing" temperatures).
- vortico 7y agoIsn't 1000 psi almost a km deep? Not sure if this would work at all.
- kijin 7y ago1000 psi would be 700 meters under the water. There are actual diving watches that are rated for 1km or more. The first image on the Wikipedia page for "diving watch" shows one rated for 3km. Rolex famously attached one of their prototypes to the exterior to the Trieste in 1960, and it survived the trip to the Challenge Deep. [1] https://en.wikipedia.org/wiki/Diving_watch https://en.wikipedia.org/wiki/Diving_watch
- lb1lf 7y agoGerman manufacturer Sinn makes a watch - the UX - which is rated (if I read the specs correctly) to keep time to 5,000m (16,500ft.) and work after being at the bottom of a km-deep bore hole at the bottom of the Mariana Trench - the case is rated for 12,000m/39,500ft).
- Someone 7y agoThe petroleum jelly I know of is fairly opaque. Is there any other? If not, even with a thin layer, I doubt the result will give you a readable display, as, judging from the red color of the display in the end result, there’s air between the glass and the LCD display in these watches.
- ComputerGuru 7y ago
- duxup 7y agoWell... trying to hack it. No confirmation if this works.
- gnopgnip 7y agoMineral oil breaks down latex quickly. What material is used for the seal? Oil expands and contracts with changing temperature. An air bubble will appear soon after if there are no special steps taken to prevent this. The real advantage of an oil filled face is the greatly increased readability of the watch.
- jhoechtl 7y agoTrue. There is a Liquid you can put on top of eg marmalade which seals it from air. I think it is a from of liquid silicone (mind the final _e !) which I think is not aggressive to rubber.
- deleted 7y ago[deleted]
- sq_ 7y agoDid a little research, and it seems like pure silicone oil is much less aggressive to rubber/latex than mineral oil (and you can get it from Amazon pretty cheaply). Does anyone have any idea what the chemical differences between the two are that affect how they interact with rubber? I’d love to learn more.
- ncmncm 7y agoGood point. Mineral oil, contrary to the remark in TFA, is 100% organic. Unlike olive oil, though, it's saturated. Does that matter? It's not exposed to air, so no. But olive oil goes cloudy when cold. The watch is unlikely to have latex in it, but quite likely to have silicone parts and seals that might soften in silicone oil.
- dvt 7y ago> Mineral oil, contrary to the remark in TFA, is 100% organic. Thanks for the correction! From what I was reading, olive oil goes rancid (and acidic; but mineral oil does not).
- deleted 7y ago[deleted]
- JamesCoyne 7y ago> I decided to switch to a reddish tint after my first failed attempt. What happened with the first attempt?
- dvt 7y agoThe buttons were misaligned with the contact pads so I had to take it apart again.
- WheelsAtLarge 7y agoI wish someone would test if it's even water resistant for a period of time in a deep pool. I bet it is. I wish he would at least done the pool test. If it's waterproof, it's a killer hack for its simplicity and overall cost.
- tushar-r 7y agoThat watch looks amazing with the red tint and that strap! :-)
- aaron695 7y agoAs mentioned it's known as rhe terrorist watch. https://en.m.wikipedia.org/wiki/Casio_F-91W#Usage_in_terrorism https://en.m.wikipedia.org/wiki/Casio_F-91W#Usage_in_terrori... Buy from eBay
- _Microft 7y agoSome sources suggest heating the mineral oil to ~50° Centigrade, but I’m not exactly sure what the reasoning for that might be, so I stuck with room temperature. The likely explanation is that heating lowers the surface tension [0] and viscosity of the oil so that it can creep easier between the parts. I also considered heating for a problem where a liquid had to enter very narrow cracks. [0] https://en.wikipedia.org/wiki/E%C3%B6tv%C3%B6s_rule https://en.wikipedia.org/wiki/E%C3%B6tv%C3%B6s_rule
- oeuviz 7y agoCould it also dissolve solved air contained within the oil, as it happens by boiling water?
- _Microft 7y agoThe liquid should be able to hold less gas at higher temperatures, yes. What you observe with boiling water though is not solved gases leaving the water but actually water turning into steam. Steam is exactly the same stuff as water, just a lot less dense. Actually if you increase temperature and pressure enough, there will be a point at which it makes no sense to differentiate between water and steam anymore [1]! Which is a fun thing: you can turn water into steam without boiling it. Raise the temperature and pressure enough while keeping it liquid, reduce temperature while keeping the pressure up and then reduce the pressure as far as you like, as long as it doesn't make the water condensate. Voilà, steam without boiling! What is happening there is taking a detour around the critical point instead of crossing the blue line (which is where water boils) in the following graphic[0]: [0] https://en.wikipedia.org/wiki/Critical_point_(thermodynamics)#/media/File:Phase-diag2.svg https://en.wikipedia.org/wiki/Critical_point_(thermodynamics... [1] https://en.wikipedia.org/wiki/Critical_point_(thermodynamics) https://en.wikipedia.org/wiki/Critical_point_(thermodynamics...
- sq_ 7y agoThis is super cool! Kinda want to try it next weekend... Seeing a lot of commenters wondering if the seals on the watch will manage to keep water out/oil in. Anyone know if it's possible to replace the o-rings or anything like that?
- godzilla82 7y agoThe entire watch is 10$.
- sq_ 7y agoYeah, I’m aware. I wouldn’t really care if the watch itself died, but leaking oil would be a bit annoying and making things that should fall apart last longer is often a fun challenge.
- hoseja 7y agoYou could pull vacuum over the oil bath to positively coax all the air bubbles out of the watch.
- Jerry2 7y ago>You could pull vacuum... Unfortunately, that would also destroy the LCD and quite possibly the crystal oscillator (not sure how strong the metal can enclosure of those things are). Battery wouldn't survive it either but you could easily take it out and insert it after the vacuuming.
- londons_explore 7y agoThe metal can for the oscillator surely doesn't fill with oil, and would therefore crush at 1000 psi? Filling this with mineral oil might actually reduce rather than increase its pressure withstanding ability.
- Jerry2 7y agoI have no idea how tightly those things are sealed. Given some of the watch tests in this thread (the olive oil one), it surely can withstand the positive pressure but I'm not certain it could withstand negative pressure. If oil got in there, that oscillator would never keep the correct frequency again. Hopefully someone does some tests.
- deleted 7y ago[deleted]
- Theodores 7y agoHow does the piezo buzzer get affected by this? Is the alarm louder or quieter? Is the tone any different? I have no plans for deep sea diving any time soon, however, I do like getting up in the mornings. Would an oil filled Casio help me in this practical regard? I also wonder about how fragrant the oil could be, if you used some oil based perfume, could the watch that is not waterproof be made to smell nice, if only slightly so, but mitigating the odour of bacteria that accumulate on the back of the watch when tightly worn?
- dvt 7y agoThe buzzer is definitely more "muted" but still beeps! I'm not sure if a fragrance would "keep." I used odorless mineral oil so I can't give much insight.
- johnnycab 7y agoI like the F91W because it refuses to die, keeps good time, has as an alarm and a hour minder. However, to repurpose it into some kind of frankenwatch to behave as a diving watch, is counter-intuitive to the fact that, it will lose most it's useful features, freely admitted to by the author in the article.
- maltenuhn 7y agoBefore this became the de factor standard in tech dive computers, advanced divers would often do the same and fill their units with mineral oil. For anyone interested in how this can go wrong, Raising the Dead - a book about scuba diving at its limits - has a passage about a rescue diver repairing his dive computer in the field, re-filling the oil, and noticing that he'd lost a drop or two in the process, with a resulting tiny air bubble...
- gnode 7y agoI wonder whether any mechanical watches could cope with this technique (and maintain any semblance of accuracy).
- sq_ 7y agoI'd imagine that any mechanical watch in which the mechanism wasn't designed with the viscosity of oil in mind would be completely incapable of accuracy if one were to add oil.
- jacknews 7y agoWhat's the problem with the LED, does the liquid filling cause TIR off the watch-face/external air boundary? If that's not the problem, you could try side-mounting the led, as here: https://www.instructables.com/id/Watch-LED-Light-Mod/ https://www.instructables.com/id/Watch-LED-Light-Mod/ Does the oil leak out of the buttons when they're pressed? How about the buzzer? I think it's attached to the back of the watch so shouldn't be affected too much? Someone mentioned improved readability. I assume underwater that is definitely the case, as you no longer get TIR reflections off the back of the watch-face/internal air boundary at steep angles, but how is readability affected in air?
- mattmoose21 7y agoDoes anybody know what dyes he used?