12/03/2021.

Lighting

Current pickup by conductive bearing

I am going to equip all axles with conductive bearings. Many enthusiasts have complained about the rapid wear of plastic bearings. But as it is difficult to use commercial brass bearings, which require digging up the axle boxes, I will make bearings out of thin brass sheet.

The bearings have a ø 3 entry. I had made a stamping tool for ø 2 bearings for DEV REE and De MassinI Romilly coaches.

Bearing stamping

Finished stamping

I need to make a new one with a larger diameter to ensure centring, except for the central axle where I prefer to leave a float.

The strip is made of 0.25 mm thick brass. The punch is made with an old broken ø 3.2 carbide drill ground to a cone with a diamond disc. The die is a 2 mm stainless steel sheet, also hollowed out more or less in a cone with drills of increasing diameter, as I don’t have a suitable milling cutter, then ground with a corundum wheel.

To avoid random tearing of the brass, the strip is drilled to ø 0.5 before stamping.

The bearings are tinned and receive fine wires (ø 15/100) from flexible cables on their upper edge. The gluing is done with CA glue. The bearings are held in place with a 24.7 mm axle (Roco).

Gluing of the bearings

Move the mouse over the picture to see the details.

The bearings of the central axle are not glued, they remain floating, otherwise there is a risk of jamming the sliding axle holder, or derailment due to non-planarity.

Wire routing

The wires are routed through the chassis via ø 0.8 holes located near the suspension shackles.

Here is the drilling diagram:

Drilling diagram

For the movable central axle, the wires are longer, in a zigzag pattern, to accept deformation without risk of breaking.

Central bearing

Copper tapes are stuck to the edge of the chassis; they are about 70 mm long. The soldering should be done in the area where the ballast is visible. Care should be taken to ensure that the solder pads are not too large and do not come into contact with the ballast. Flexible wires are soldered to the tapes near the toilet where they will exit to connect to the lighting strip.

Wheel sets

The insulated wheels are made conductive by rings made from three different diameters of brass tube. Alternatively, the silver painting technique can be used. The axles are cut in half and chamfered, then joined by a 14.2 mm long polystyrene sleeve.

Lighting strip

There are eight bays of seats, plus the platform: that’s nine LEDs. Each has a forward voltage of about 2.5 V, and being wired in series, they must be supplied with a voltage higher than 22.5 V. A voltage doubler circuit, giving 30 V, is necessary.

As a reminder, the advantage of putting all the LEDs in series is twofold: it simplifies the circuit design, and this solution consumes the least current, and therefore requires relatively low capacitance capacitors for flicker suppression.

The two 100 µF capacitors in the doubler have their wires bent so that they fit easily into the toilet.

There is a central reed switch for lighting and another at one end for possible tail lamp control (not installed in the photo).

Lighting strip

Note: a new circuit, requiring only one electrolytic capacitor, was designed too late to be applied to my coaches, as I had already received the previous ones.

Tail lamps

Here, removable lamps are not an option, as there is no free space between the end wall and the seats to install a connector. Only very thin wires will fit between the plastic wall and the paper decoration stuck to it.

The wires are routed through a ø 0.5 hole drilled just above the lamp holder.

The REE lamps, equipped by me with SMD 0603 LED, are glued (with difficulty) to the lamp holders after having scraped their paint which adheres very weakly by the way.

Lanterns, external view

The wires run up against the end wall and are hidden behind the self-adhesive decoration (see next page).

Routing of the lantern wires