IMG_4213.JPG This was Sir Edmund Hillarys Everest watch I believe
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Wow, I love the Everest with the acrylic, looks amazing, great work
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IMG_4213.JPG This was Sir Edmund Hillarys Everest watch I believe
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Great looking mod. I was buying a replacement crystal for my prs29a so I added in a M Sternkreuz 31.4 (M314). Has anybody fitted one like this yet? (No ring). I'll keep it on the back burner and keep an eye on this thread to see how this mod develops. I do quite like having the sapphire but acrylic does look cool.
I think it might have been KevG who had one fitted without the tension ring.
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Hi Gent,
From the modding perspective whats the difference from with or without a tension ring?
Does the 'without' pose a greater risk of the crystal popping out? Or does it use the existing tension ring?
Could you enlighten please as I think this will be a questions asked again perhaps.
Pardon my ignorance on the mechanics.
Thanks.
Good questions.
The tension ring is a steel ring that sits inside of the crystal edge. Sometimes these are referred to as armoured crystals.
The principal thinking is that this has the same coefficient of thermal and pressure expansion as the steel case of the watch. So, the case itself expands slightly under pressure and the tension ring does the same, so the crystal is kept secure.
The acrylic crystals without a tension ring are actually bigger in diameter than the opening are compressed in order to install. In theory that stops it from popping out in every day use, but its when the watch experiences a change in pressure where it might be an issue (underwater, on a flight etc...)
Hope that makes sense?
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Generally, a tension ring crystal is required to give water resistance, there are exceptions but for an acrylic crystal to have the resilience to seal it needs to be thick, not a design I favour but it does work. However, in these situations the crystal is bespoke and that creates problems if it needs replacing.
In theory, the comments regarding expansion are correct, but over the temperature ranges that a watch experiences these effects are minuscule.
Tension ring crystals are available in increments of 0.1mm, they fit tightly and they should require a press to fit, if they fit with thumb pressure theyre too slack.
Im not a fan of modifications but I think the acrylic crystal mod to the PRS 25 is a nice one that improves the watch.
Thanks both for that information.
So without a tension ring applied the potential water resistance may be limited?
I should look back through the thread... whats the visual difference in terms of the renault? If i remember correctly the height of the crystals with and without a tension ring were the same.
I think that the tension ring was brush finished too?
Thanks gain really helpful information.
Well in theory the water resistance is better with a tension ring fitted. My tank only goes up to 6bar and it was was fine. As I recall the member who had the acrylic crystal fitted without the tension ring said the watchmaker that did the modification said it also passed a pressure test.
The rehaut will be the same, but you see the tension ring in mine at extreme angles. As you rightly say, I brush finished it to get it to match.
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And for those interested - this is now over in the sales section!
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Yeah, tested to 6bar without the tension ring
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Cheers.
Its a fairly straightforward swap, hardest part was adapting the tension ring if Im honest (and playing around with different crystal sizes to get the right fit!).
Im potentially going for a gentle domed sapphire crystal swap on the gilt instead of the acrylic. Not sure just yet which way Ill go. Enjoying this amazing dial though. Lovely lovely watch.
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Finally, got my Everest back from the crystal swap job, pressure tested and regulated, all good to go!! Loving it all over again.
Thanks, Gent for the tips on the mod.
Enjoy the pics below...
Before swap with stock sapphire crystal...
After swap with the Sternkreuz ATCR 31.4 armoured (tension ring) acrylic crystal....
View from an angle....
The warmth of the acrylic and the nice distortions at an angle is really great.
The crystal really makes the watch
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A few questions on this acrylic mod:
1) How much thicker is the watch with the domed acrylic?
2) Is the seal compromised? Is it still 100 m WR?
Yes, post #110 shows thickness...
13.4mm vs 11.3mm on the original.
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I suggest caution if you're considering converting. My manufacturer is holding 350 Everest cases for me and I asked him if he could case an acrylic crystal version for me to play with and he said is wasn't possible because the case has to be manufactured differently for acrylic.
Eddie
Whole chunks of my life come under the heading "it seemed like a good idea at the time".
I am a very happy owner of 3 Everest 36's in various guises. I really enjoy them, and am 'content' with the sapphire. Fast forward to this month, and the realising of my desire to get the PRS29A. I was also torn as to whether to add the 29AM to the order and did. I was building myself up to 'love' the A and 'like' the AM, but when I received them, its the other way around. I have to admit to being disappointed with the sapphire on the 29A, and have taken a pic of the 25 and 29A side by side clearly showing the more pronounced milky ring on the 29A. I don't think I can be content with it and now want to look into changing its crystal for acrylic (I dont want fixed bars). I have tried to find some posts discussing whether any member has attempted it on a sapphire 29, and also whether the PRS-25 and 29A/AM crystals are the same diameter. I also believe that sapphire can be done really well, and almost look as good as acrylic. Take the Railmaster 57 trilogy LE, and you'll see what I mean. I also own a Max Bill 2018 LE which is fitted with sapphire that (to my eyes) looks identical to acrylic (I have included pics in this post). If it was possible to use a similar crystal shape on the Smiths models, it would be a true game changer (and for me anyway), negate any desire to go acrylic.P1030901.JPGP11030902.JPG
Last edited by mkildare; 29th March 2021 at 01:37.
Another pic of the Max Bill sapphire. (apologies, but I am really struggling to add images to my posts properly)P1030904.JPG
Im sure I saw a post where someone had changed the crystal on a sapphire PRS-29A to sapphire, although I cant find it right now. Will keep looking.
I 100% agree that a truly domed sapphire crystal in the style of the ones you are showing would be amazing on the Everest.
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Wow - that looks so much better! It's great to see the outer 'track' clean and unobscured.
@Mamaw. I would be grateful if you could share the details of the acrylic crystal. I REALLY want to make the swap!
Thank you - its much appreciated.
Thank you for that! If I have the nerve to attempt the swap, I promise to post a pic or 2 of the result
Really like this, a lot.
Is the current models ring caused by a step / angle change in the crystal, as opposed to a dome?
If your talking about the "milky ring" - then just Google milky ring sapphire - and you will get a ton of information. But the short answer is yes - the sapphire with a dome - is a faux acrylic. The sapphire Crystal I with is stepped rather than curved, and is is thicker at the step - so you see the thinkness. https://youtu.be/R21hgz-A7JY
I've been looking again at the sapphires on my 2021 PRS-29A and 29AM's, and comparing them with some side and front-on close-ups of a 2019 version currently on eBay. Through a loupe, I can see that both my watch 2021 crystals have a definite corner (or edge), both internal and external, and I am convinced that this is making the milky ring far more pronounced on the current release (the milky ring ends abuptly at the internal corner). I have come to the conclusion that my ideal scenario would be to replace my current sapphire crystals with the exact ref that was factory fitted to the 2019 models - that would make me very happy (and in my case, preferable to replacing them with acrylic)!! Aother option, of course is to sell my current 29's and pay over the odds for 2019 versions. I suppose I could also remove the current crystal, measure it with a micrometer, and go on the hunt for high-dome sapphires. Yes, its a bit of a faff, but if any watch is worth the effort, its the PRS-29...
If a sapphire is a faux acrylic curved high domed sapphire - then I would think that it is very difficult to avoid the milky ring - in ordet to avoid it, then the sapphire would have to be thin at the eges, because it is the thickness that gives the milky ring.
So thin edges on a sapphire would require a lot of expensive milling and it would probably make the crystal brittle. But it would certainly make for a very expensive curved sapphire crystal.
If you don't like the milky ring, I think your best option is flat sapphire or curved acrylic.
Last edited by Mads Gorm; 21st May 2021 at 23:31.
Yes, I agree - and thank you for your wise advice! I've just ordered a couple of Sternkreuz HW 324 acrylic crystals from Cousins, as per Mamaw's earlier post. 2 very last questions - I already have a crystal press to remove the sapphire, but I assaume that I'll need to purchase a crystal lift to fit the acrylic replacement. Will a cheap 10-15 Amazon/eBay lift get the job done OK?
Last edited by mkildare; 22nd May 2021 at 13:53.
Post resurrection - second version here:
https://forum.tz-uk.com/showthread.p...crylic-Mark-II