Kimmo 

So I've done a custom Di2 loom, using three of the hugely expensive wires to give me a plug each for shifters, derailers and battery, and also spliced onto the BCR2 since I've deleted the the charging port (that plug and jack is actually repurposed to sit between the frame and fork, in the top of the downtube).

The SM-EW90-A is now just a tiny PCB inside the stem, hotglued into a section of sealant gun nozzle, which locates it and also serves as a light pipe to a small hole in the top of the stem, plugged with hotglue - it looks just like a 2.5mm LED! Sweet. There's a headphone jack from a phone for the ground and signal, plus the junction A button (just contacts ground, so only three wires needed), which is moved up just behind the right shifter. It's a pretty trick retromod if I do say so myself... had to make a couple of 1.8mm holes in the carbon steerer, a 2mm hole in the bars (in the lower part of the section looking into the stem, fingers crossed those fibres weren't too important), a 3mm hole behind the FD, and a couple of 3mm holes in the BB shell to the seat tube and chainstay (they could've been smaller, but those drillbits weren't long enough). I reckon I've probably avoided any serious structural compromise.

Anyway, throughout the process, I've been hooking it up to E-tube to check if stuff's working (I was waiting for the levers to turn up), and I could get it to recognise the battery, A junction and derailers okay, but at one point I managed to stuff up the wiring and E-tube would spend a bit longer on the detection dialog and then just go back to the 'connect the bike' screen. Luckily it wasn't bricked that easy, when I fixed the issue it worked fine again. I was connecting the BCR2 via the 3-port connector I'd hacked off the A junction into one of the shifter plugs.

So then my levers turn up, and I hook em up, and start adjusting my derailers, all good. Then I hook it up to the PC, wanting to configure syncro shifting, and bloody E-tube does the nope thing again! Bastard.

Only this time, there really doesn't seem to be anything wrong with my wiring, since the system works... it's a bit weird, and something of a stumper. The only thing I can think of, is maybe the levers aren't entirely compatible with the derailers? But the derailers have the latest firmware, and are meant be compatible... I dunno. Maybe ditching the charge port isn't entirely kosher, since when I tested for continuity between the + on that and the + in the main loom, it's not the same input. But, I had it working like that.

Any ideas...?

ETA: oh wait, I know - I've plugged the BCR2 into the sprint button port! Doh! I bet it'll work when I move the plug...

...Yeah, that was it, lol. I guess I'll make this a build thread and post up some pics.

ETA2: NEW INFO GLEANED ABOUT Di2

There's lot of great info on Di2 here: https://bettershifting.com/ but I haven't seen anyone else cut open an A-junction or do their own loom, so here's some new info that may be useful to anyone who follows - the system seems robust enough to survive being connected up with polarity reversed (oops!), at least between A-junction and battery, the button on the A-junction only needs a single wire taken from it to make it remote (one of the contacts is ground, same as the black wire), and if you use a headphone jack to separate the loom between bars and stem, it's hot-pluggable, at least if you wire it with the + on the end of the plug, - on the back, and the button in the middle.

Kimmo 

Teaser:

Kimmo 

You might wanna play it at 1.25 or 1.5x... my video production is a bit crap

Kimmo 

Going the hack on cable guides:





Here's a trick I came up with to stop the file skating off into the paint:



With the dip in the middle, it's a lot easier to hold it square.

Kimmo 

I started mousing the frame with a front brake cable offcut, the welded end ground smooth and the cut end taped to some twine (had no fishing line). Used a bit of liner tube here and there to help.



The twine was pretty crap. Needed something a bit stiffer, so busted out some ABS 3D printer stock.



I did use the twine, plaited with the loom wires, to add some fuzzines to the wire, and used extra length and coiled it to try and mitigate any noise... Joining stuff to the printer stock without creating a snag point was a bit of a trick.

Kimmo 

Bought some diamond bits for my Dremel to do the holes in seat tube, bars and steerer. Had to use a bit shaped like a sharply tapered cone with a little ball on the end to soften the inside corner of the hole enough to be able to drag the wire through - no poking it through when the steerer's inside the head tube.



These holes are about 1.8mm.



Repurposed charger plug, with most of the bulk hacked off it



Ditto for the jack. This had an O-ring on it... when I took it off the jack, I expected it to be a normal O-ring, but nope. Square. Shimano doesn't take any shortcuts; the EW50 wires I hacked up for the plugs are that expensive because they're the toughest wires anywhere near that size I've ever stripped.

Kimmo 

Here we can see that pair of connectors hotglued where the downtube meets the head tube. I had to leave extra length on the wire to be able to do this, and the knot leaves me the right amount of slack between the glued plug and the steerer after I've inserted the fork and dragged the excess wire out.



Fiddly business. Phew



Here's where I discovered that a couple of little holes in the top part of the expander plug (not shown here) wasn't enough; I also needed to file a groove through the lower knurled section and O-ring groove, to allow me to push the expander plug down into position. The upper hole in the steerer was originally going to be bang in the middle of the stem's height, but something told me it'd take away less strength if I moved it up to just below the upper knurled section.

Kimmo 

Check out the SM-EW90-A PCB! Some really tiny surface-mount stuff on it, like in a phone.



First go at wiring it up



A pair of wires runs back into the steerer and up through the compression plug to join the wires coming from the frame up through the steerer. This join has to be unsoldered to get the stem off, since there's no room for a plug under the top cap. Initially, another two pairs of wires was running forward into the bars, the extra pair for the remote A-junction button. Finding a suitable connector for four wires was a PITA. Surface-mount micro USB jack gave barely more than a pinprick-sized area to solder onto



But with the aid of my phone on a tripod running a magnifier, I did it by employing ye olde Ultra DMA HDD ribbon wire. Of course, it promptly shat the bed during assembly with the hotglue and heatshrink.

Kimmo 

Plan B, ditch the wire I suspected was surplus to requirements - there's like 0.3ohms between one of the contacts on the A junction button and the black wire in the the Di2 loom, and whaddayaknow, that's the go. So here's a far less hair-tearing headphone socket from the same pillaged phone.



Also shown is the section of glue gun nozzle I carved up to serve as a mount for the PCB and light pipe for the LEDs. PCB hotglued into it



And here we've got my $40 wing and a prayer Aeronova ripoff with a 2mm hole in it. After considering it, I decided to put the hole as low as I could, which seemed to make a lot of sense.

Kimmo 

I initially got my order of operations a bit screwed up, and found myself having to drill the hole in the stem with it on the bike... not good - it came out a tad off-centre. This was during plan A with the four wires, so the thing had to come off again. Luckily this hole was only 1.5mm, so with a bit of careful dremelling with a skinny diamond bit, I widened it out so I could make a nice 2.5mm hole on centre.



Looks pretty freakin' sweet with a blob of hotglue in it, nearly as good as I hoped for. Very slightly countersunk by hand to deburr it, a bit of black marker in before the glue, and it looks mint. Maybe a dab of epoxy on top to make it flush...



Little bit of wire to hold the RD cable just so



FD cable neat AF

Kimmo 

Here's the battery, shaved about a mm down each side to fit into the seat mast (I filed along the join, down to the groove, didn't go through the casing), with a couple of tiny holes drilled in the square bit on top, where I've got a bit of wire rigged up to orient the thing for removal. Kevlar string attached to that, wound around some rolled-up bubble wrap.



This lot gets stuffed down the seat tube as far as possible with a large poking implement of some sort, and the end of the kevlar is secured in the top of the seat mast with a small blob of blutack.



Ta-daa! Pretty much finished. Just gotta take it for a spin and dial in my position (I've swapped a 17/110 for this 8/100 stem), fit a little button onto those bare wires, and get some fresh bar tape on there.



I'm pretty stoked with the result

Any questions?

Kimmo 

Running out ideas for fettling the weapon... All I've got left is minimise the gap between fork and head tube (gotta find a way to evenly remove metal from the bottom of the crown race seat, one of those ones with a split), use some dark tint film or gloss black paint to style the 7400 brake to match the 9000 gear, and maybe integrate a front light?

Suggestions welcome.

blamester

Top drawer stuff.

noodle soup

Definitely looks better than when you had SRAM wiped all over it.

Kimmo 

Geez you hate SRAM! I actually reckon the Red derailers look a bit better than these, although these levers are obviously sleeker. Biggest cosmetic difference IMO is a missing set of cables.

Kimmo 

Got around to dialling in my new position (getting old, changed my stem from 17/110 to 8/100), got some fresh bar tape, pillaged the middle-click button from a mouse



Here's a shot of the hidden A junction doing its thing



Once I figure out where I want the levers, I put a lot of effort into making them symmetrical



Glass is flat



Lots of trial and error, due to the fact the height changes with rotation

Kimmo 

Oh yeah

Iride01 

So what is different about it? Sorry... I just don't have time to read everything. Maybe you said it initially, but I forgot by the time I made it down here.

Kimmo 

Um, It's a pre-electronic era bike made full internal Di2-only with a custom wiring loom incorporating the guts of an A-junction inside the stem. I'd have thought such a thing would've warranted a bit more appreciation round here...

Oh, and I found out three things about Di2 the internet apparently doesn't know yet, you're welcome.

Iride01 

Oh....

Sorry, I just didn't pick up on what you were trying to show us. I got too bogged down in the details and never saw the bigger picture. Which in all fairness I think you might have presented better in the opening paragraph.

It is a big accomplishment and I'm sorry to sound like a debbie downer. Though I felt a little left out on what and why some things your were doing. I.E. what was the circuit board? I'm assuming it was the guts of the old style junction A box, but really not certain since all my Di2 is the newer stuff.

Regardless, now that I understand what you were showing us, Good Job!

Kimmo 

Righto, I'll edit the OP again at some point.

Yeah, that's right, it's the SM-EW90-A. What else were you wondering? Did you check out the vid?

Iride01 

Where is your charging port? Or is that the 2.5 or 3.5 mm headphone jack you show in post #9.

Somewhat wondering why you went to so much trouble to go through stem and steerer. Wouldn't going into the top tube with or next to the rear brake cables have looked so bad? I'd be happy with the look to avoid the future hassles.

Otherwise good job. I did watch your vid. I just don't want to be there in real time while you ponder things. Though it did answer some things I was wondering.

Broctoon

I can appreciate what you’re doing. Looks like some pretty resourceful solutions and top notch DIY engineering.

For my own bikes, I still like mechanical components. When the time comes to jump into electronics, I’ll probably go wireless to avoid most of these hassles.

Kimmo 

Charging port is deleted. You can just splice an e-tube plug onto the charger and use that instead. As mentioned, the charging plug and jack were repurposed to split the loom at the head tube for fork removal. The headphone plug and jack split the loom for bar removal.

Rear brake cable runs external, like the shift cables did. I might see about changing that, if I can get onto an old boss who works with carbon... But yeah, full internal, because it's sexy and I could. Not concerned about the hassle; I've obviated most of it with the plugs and jacks. That loom is married to the frame now, since it's now dedicated to Di2.

If any YouTube vid is too slow for you, you can click on the gear icon and play it faster, like I recommended.

Kimmo 

It's all about the porn factor, which is why it's rocking 9000