That’s one thing I thought of when looking for connectors. Absolutely impossible to find these days. There’s just no market for slim ethernet connectors anymore. When Lenovo couldn’t fit an ethernet port onto some of its recent laptops (without TB), they opted to use an internal ethernet controller and proprietary dongle for the PHY.
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Never use a hinge with these working parts, let alone a 3D printed hinge. Just use a full size port.
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Can’t just be me who always wondered how these XJACKs worked, eh? got one on ebay for a tenner. glued shut of course
To my surprise, they actually have a flat flex cable between the ethernet port and the board. I figured this was how you’d do it nowadays, but I was not expecting flat flexes to be used in 1999! The actual mechanism of the popping out is pretty simple- it’s push push, like a pen.
The actual ethernet jack is more interesting, though still rather simple. The plug is held in remarkably securely by the top tab. When you insert the cable, a small wire stops you from pushing too far, and the contacts spring back as they enter the contacts on the plug (they are very springy. if you don’t push the plug far enough to lock, they will push it out).
The whole card is 5mm thick, and the ethernet jack is 4.25mm thick and 17.6mm wide. However, it is quite long:
(black box is the size of an expansion card)
So thickness wise- yeah, it cooould fit in an expansion card. But keep in mind, there also has to be room in there for the electronics!
Janky quick check in fusion- if you have an “upside down” 0.8mm PCB, you can get a 4.25mm (there is probably room to make the whole thing thinner, but this is a known good baseline) space, and still have a 0.6mm thick bottom on the card. In this setup, you’ve got 1.15mm of space above the PCB- not a lot- you’d need to double side assemble stuff like transformers and the FFC connector onto the bottom, but enough room for passives and maybe even QFNs, like the ethernet controller (fortunately just one chip these days
)- probably best to have the jack offset to one side of the card, not in the centre, to save some room. There’s 25mm from the front to the back of the USB-C plug- perhaps just enough? 25mm goes to where the flex cable comes out on the XJACK, and I think there could be some space to save there- plus you can obviously go all the way to the back of the expansion card at the side of the plug, perhaps for the spring mechanism.
So, yeah. MAYBE doable- if you can acquire those spring contacts, and house those in a (3D printed??) jack. Would be easier to stick to 10/100- gigabit requires a bigger controller, and twice the magnetics- not to mention the potential signal integrity issues of running gigabit through a flat flex, even a short one.
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As far as I remember, the HP elitebook 840 g5 has a little different ethernet connector. The top part of the jack is part of the base and the lower part of the connector opens up like a glove box in some cars. We got some of those HP Laptops at the institute, so I could provide measurements, if needed.
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If you scroll up in the thread, you can see that was the first thing I looked at unfortunately, there’s only barely enough room under the Framework. Plus, a custom RJ45 AND a very tiny hinge would be required. That’s why I decided to have a look at this instead.
Also:
don’t go poking a screwdriver into your ethernet ports (or do, I’m not your mum) but did you guys know that all RJ45 jacks are a bit springy?? I certainly didn’t until I just took one apart- might actually be pretty easy to get these out of existing ports 
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@ExplodingWaffle sorry for not being up to par here. I must have overscrolled this.
Still, looking forward to the final ethernet jack, I plan to use the framework as a data aquiring system and our labs are better equipped with ethernet then eduroam Wi-Fi
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I doubt this will be durable, you would require a cover to prevent shorting out the contacts which would require some kind of hinge.
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That’s what I’m hoping for. I would buy an ethernet expansion slot like that in a heartbeat.
Pic of the folding style ethernet jack from a Vaio laptop:
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@ExplodingWaffle could you possibly shared your models that you’ve used when testing/measuring in this thread? I’d like to have a play with some ideas myself; be great to be able to reuse what you’ve already done if possible
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I don’t know if anyone is still thinking about this but once I read through it I thought of the port that Fujitsu uses in their laptops. They have it collapsible and slides in and out of the side of the laptop.
@Daniel-L
already mentioned above
but I agree - would be nice if someone could offer a teardown or something for some kind of reverse engineering
Cant remember where i heard it but 95% sure those existing collapsible designs are completely proprietary and not open to be used by other manufacturers. They aren’t framework, after all. You could try reverse engineering but wouldn’t recommend it, they might come after you for patent infringement.
Wow! Amazing project, love that someone’s actually attempting it rather than speculating that it can’t be done based on measurements!
Really good work, keep it up! 
So you have a working prototype? Is there a STL or something of your case design and BOM for assembly? Even with the noted shortcomings, I’d much rather had one of these than the ‘official’ ethernet expansion card.
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A view of a similar Dell implementation, also disassembled. It does seem too thick for the Framework, but the design created above with the flap should work.
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I wonder if, instead of fitting a huge spring-mechanism in the card, it would be easier to just fit that small cable in there?
So when you want to use the port, you completely take out a foldable Ethernet port that is connected with that small cable to the expansion card.
Of course pulling on the Port while it is out of the expansion card would rip of the cable from the PCB, but that is something we could try to solve after i have heard your opinions to that idea.
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The XJACK is great for temporary use, but I’ve always feel bad about using it as a long-term connection. Even on a desk, it’s so fragile, I’ve seen many of these get mangled up. 
The other thing that makes it feel more like a “temp solution” is the way the cable connects, it would have to stick up then over, so another thing to make sure you don’t snag on.
However, an option like the XJACK on an expansion card would be nice for those who’s use case is to only use it for emergencies and/or quick/temp connections (troubleshooting network equipment, for example). For that purpose, I personally would want such a card for my FW16.
The question is… is the XJACK patent expired yet?
The Verge covered this, and has an animated GIF of it that I think is pretty cool.
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Interesting effort, with the FW16, is there same height issues, or will the 16 manage to have enough room?
It is fully compatible with all existing expansion cards and therefore has the same height limitations.
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