The F-91W is such a fun little watch[1] and people have done the weirdest stuff with it. There's a guide to make the mod on Youtube[3]. There's also the TOTP in a F-91W[2]
FWIW, a correction is required here. Oil-modding a F91W will NOT make it a dive watch replacement as the video creator claims several times.
A dive watch is designed to be operated at that depth while the weak o-rings around the pushers on the F91W will give up when you use the buttons. Oil modding on it holds up during a dive as long as you'll never push the buttons, so it's more of a neat party trick for show than anything to daily drive.
For watch hackers, there is an alternate PCB with programmable microcontroller available for the F91W https://www.sensorwatch.net/
I got one for Christmas and it has been super fun to hack on. I programmed a new face for mine that displays the current tide level, and next high and low tides.
Casio is phasing out electroluminescent backlighting and going back to a single LED, so I would buy an F105 while you still can. I've heard it said it was to improve battery life and longevity but I've never had a problem with either one.
There’s an algorithm you can use to calculate future tides but it’s complex and I wasn’t sure it would even run fast enough on the watch. I gave up after a few hours and ended up generating an array of high/low tide levels and times for the next few years. NOAA has all the tide data you could possibly want, and an api to grab it.
Yeah but.. it’s just the way of gases and liquids under pressure. Even if you could sustain the pressure with gas it would be an unnecessary implosion risk if it’s pierced. As long as it still functions fully including on the surface, I wouldn’t qualify that as cheating. More like us biological weaklings who need ~1atm can be cheap and skip the liquid/resin because if we accidentally end up in space or the deep sea we generally have bigger problems than checking the time.
I've read that it's possible to breathe oxygenated liquid perfluorocarbons, but something about the idea is just terrifying to me. I think it's the "fluoro" bit specifically that scares me, even moreso than the "liquid" part.
I've been stuck down the Casio modding rabbit hole as of late. I knew filling the watch with oil ('hydro-mod') lead to a crisper display with better viewing angles and increased water resistance, but to see a watch with minor splash resistance operate as such depths is insane.
Worth mentioning some drawbacks before you get your precision screwdrivers out. Doing it will make your watch get stupidly hot in the sun, the process can be messy, and sometimes certain mechanisms/features can break as a result of it. Best to check what others have done before you.
So the link to espionage is that a spy diver can dive to -5km wearing that watch and the watch will stay whole.
ChatGPT can be really stupid sometimes.
Was disappointed that he only brought a modified oil filled watch to 5km underwater. Would have been interesting if he’d have strapped a stock watch next to it so we could see when it would break.
These watches often have a quartz crystal - the little can would crush and the oil would damp oscillations, so they might have a laser trimmed RC loop - which would be cheaper as well as crush-proof?
Notably, there was no attempt to operate the watch at such depths. Pressing a side button would be an interesting test, for instance. Many "water resistant" watches, rated to a certain depth are only rated so, given the not inconsiderable caveat of not being able to operated - just looked at. The higher end, more expensive models claiming full waterproof ability don't typically have such functional restriction.
It seems like actually pressing a watch button at that depth would be quite a feat of precision engineering itself. Are ROV arms typically that precise that it would be possible to see well enough and finely enough control the arm to press the button?
The F-91W is such a fun little watch[1] and people have done the weirdest stuff with it. There's a guide to make the mod on Youtube[3]. There's also the TOTP in a F-91W[2]
1) https://www.youtube.com/watch?v=r6REKCs4-1M
2) https://blog.singleton.io/posts/2022-10-17-otp-on-wrist/
3) https://www.youtube.com/watch?v=jLmAq0epfrI
https://www.reddit.com/r/F91Ws_on_NATOs/comments/f9udxl/the_... also deserves a mention here, and /r/f91w for more general stuff.
> https://www.youtube.com/watch?v=jLmAq0epfrI
FWIW, a correction is required here. Oil-modding a F91W will NOT make it a dive watch replacement as the video creator claims several times.
A dive watch is designed to be operated at that depth while the weak o-rings around the pushers on the F91W will give up when you use the buttons. Oil modding on it holds up during a dive as long as you'll never push the buttons, so it's more of a neat party trick for show than anything to daily drive.
I found one of these while free diving. Wiped it off and wore it for several years, until I lost it while free diving.
For watch hackers, there is an alternate PCB with programmable microcontroller available for the F91W https://www.sensorwatch.net/
I got one for Christmas and it has been super fun to hack on. I programmed a new face for mine that displays the current tide level, and next high and low tides.
Yes, it's great fun: https://blog.jgc.org/2022/10/pimping-my-casio-with-oddly-spe...
Too bad it doesn't support the F105, aka "F91 with a usable light".
Casio is phasing out electroluminescent backlighting and going back to a single LED, so I would buy an F105 while you still can. I've heard it said it was to improve battery life and longevity but I've never had a problem with either one.
Where did you get the data for the tides?
There’s an algorithm you can use to calculate future tides but it’s complex and I wasn’t sure it would even run fast enough on the watch. I gave up after a few hours and ended up generating an array of high/low tide levels and times for the next few years. NOAA has all the tide data you could possibly want, and an api to grab it.
https://tidesandcurrents.noaa.gov/tide_predictions.html
https://api.tidesandcurrents.noaa.gov/api/prod/
Casio do have a tide watch, which presumably uses that algorithm:
https://www.greatwatches.co.uk/collections/men/products/casi...
FYI Casio recently brought out a minimalist series of the F-91W (same watch just a bit less chrome on the face) e.g. https://www.casio.com/europe/watches/casio/product.F-91WB-1A...
I own legendary GW-5000U. It is amazing to see those cheaper alternatives are as good as 5000U.
I'm wondering is there any other brend except Casio that has watches as amazing as those are.
Modified by oil-filling, though.
Yeah but.. it’s just the way of gases and liquids under pressure. Even if you could sustain the pressure with gas it would be an unnecessary implosion risk if it’s pierced. As long as it still functions fully including on the surface, I wouldn’t qualify that as cheating. More like us biological weaklings who need ~1atm can be cheap and skip the liquid/resin because if we accidentally end up in space or the deep sea we generally have bigger problems than checking the time.
easy solution: fill yourself with oil before diving. checkmate, nation-state navies
As depicted in the move "The Abyss". https://en.wikipedia.org/wiki/Liquid_breathing
Also the aliens in the Sylvia & Gerry Anderson TV series "UFO".
I've read that it's possible to breathe oxygenated liquid perfluorocarbons, but something about the idea is just terrifying to me. I think it's the "fluoro" bit specifically that scares me, even moreso than the "liquid" part.
I've been stuck down the Casio modding rabbit hole as of late. I knew filling the watch with oil ('hydro-mod') lead to a crisper display with better viewing angles and increased water resistance, but to see a watch with minor splash resistance operate as such depths is insane.
Worth mentioning some drawbacks before you get your precision screwdrivers out. Doing it will make your watch get stupidly hot in the sun, the process can be messy, and sometimes certain mechanisms/features can break as a result of it. Best to check what others have done before you.
Why does it heat up in the sun?
My guess: higher thermal mass, so over time it can accumulate more heat than a non-filled watch.
I just a fitness band in a f91w or w59 body.
So the link to espionage is that a spy diver can dive to -5km wearing that watch and the watch will stay whole. ChatGPT can be really stupid sometimes.
It's actually two separate articles in one, but they had to merge them to make the content work for their oddly specific website.
The second half of this article would make a great movie.
Any hacks to fix the useless light?
There is one, but requires another Casio watch to borrow the backlight from.
https://youtu.be/9-jd_7eXACU
Buy a W-86-1VQES instead.
Was disappointed that he only brought a modified oil filled watch to 5km underwater. Would have been interesting if he’d have strapped a stock watch next to it so we could see when it would break.
This video might be of interest to you-
https://www.youtube.com/watch?v=iOT8XU1ss3E (Do Oil-Filled (Hydro Mod) Watches Actually Dive Deeper?)
A very similar model (A158 — they differ only in the bracelet) breaks at 200 m:
https://youtu.be/G3iMkeF8qmA
https://youtu.be/sep5Tw-55yw
The timekeeping mechanism keeps working fine, though, it's only the display that's busted.
These watches often have a quartz crystal - the little can would crush and the oil would damp oscillations, so they might have a laser trimmed RC loop - which would be cheaper as well as crush-proof?
Notably, there was no attempt to operate the watch at such depths. Pressing a side button would be an interesting test, for instance. Many "water resistant" watches, rated to a certain depth are only rated so, given the not inconsiderable caveat of not being able to operated - just looked at. The higher end, more expensive models claiming full waterproof ability don't typically have such functional restriction.
It seems like actually pressing a watch button at that depth would be quite a feat of precision engineering itself. Are ROV arms typically that precise that it would be possible to see well enough and finely enough control the arm to press the button?
Not sure if the buttons function, but the watch is displaying time in the photos, for 50 minutes of the descent at least.
"rating" is so overrated. Just say you are genius, who does not hire "old white cis males", and that it will work regardless of pressure!
For extra challenge: bet your own life on that!
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