The bogie must get holes for the bare wires coming from the conductive bearings (1), and for the insulated wires coming from the body inside (2).
For the former, I drill at the indicated locations, at the end of the path which seems to have been provided by the manufacturer, at ø 0.4. The bare wires come from a computer power supply cables.
Note the 0.5 mm wedge around the axis to raise the body.
For the others, I enlarge the pivot hole to ø 1.6, greatly sufficient for passing two wires of 0.5 mm outside diameter.
As I said earlier, the end of the internal side beams tends to get curved and comes rubbing on the wheel side. So, I take advantage that the bogies are disassembled to thin these beams, with a diamond file, which bite the plastic better than a classic file.
I have provided a connection plate, although it is not essential, but it simplifies soldering the various wires. It is of 0.8 mm thick epoxy, with maximum dimensions of 9 × 11 mm to fit between the leaf springs. It is drilled in its centre at the same 1.6 diameter as the bogie pivot, and is glued with cyanoacrylate by centring it through its hole. This plate is visible on the picture at the bottom of the page.
Here again, the path of wires seems to have been provided on the side of the bearings. The wire must arrive tangentially on the bearing shoulder. Under no circumstances should the solder flow around the body, otherwise it will not be possible anymore to put back the bearing into the axle box.
To avoid this, I made a small assembly consisting of an epoxy plate drilled to the diameter of the bearings, i.e. 1.8 mm. This plate is tightened in my mini-drill vice. The bearing in the hole is firmly held by pressing a cocktail peak hold into the drill mandrel. I use wood, not metal, to avoid heat losses.
The wire, about 100 mm long (much too long but easier to handle), is wound about a quarter of a turn on the bearing and held by tweezers. A drop of Bergeon flux (free advertising) is filed. I melt very little solder on the iron tip, then I put it on the bearing. A little sizzle, and it’s done. The wire that protrudes from the “bad” side (here on the left) is cut flush.
Attention: due to symmetry, it is necessary to prepare half of bearings with wire going to the right, as here, and half with wire leaving to the left.
Note: with increasing experience, I happened to operate in vivo, without removing the bearings from the bogies, and of course without anaesthesia. In this case, I make a space in the plastic with a small ø 1 mill bit, near the bearing; I place the connecting wire, Bergeon flux, and I solder directly with very little tin, and very quickly. It is a bit risky, but much faster. It is necessary to rinse carefully to eliminate the flux, which is acid and electrically conductive.
This is undoubtedly the most tiresome part, because some bearings do not hold in their housing. I hold them temporarily with an axle without wheels. The wires are placed in their groove and then passed through their ø 0.4 mm hole. They are glued with cyanoacrylate, then finally soldered on the plate.
Before gluing, make sure that the temporary axle is loose enough, i.e. that the bearings are deep inside their housing. Otherwise, there will be big frictions, which will destroy all our efforts…
So, let’s check the axles immediately. If by misfortune an axle has difficulty turning, nothing is lost: separate the two half-axles from their sleeve, shorten one of them a little, push back the axle tip with respect to the wheel. The distance between tips will be slightly decreased, and everything will return in order. Be careful not to exaggerate: the wheel should not be rubbing on the beam, something that it already tends to do naturally!