Okay. I must start with my frustration that The LEGO Group has not provided a solution to the metal clad track that was replaced with plastic track (also known as Power Function or PF track) back in about 2009. For clubs such as the Calgary LEGO Train Club, we rely on metal clad track (silver nickel) nine volt (9V) track for shows to minimize to use plugged in power supplies to energize the track, rather than battery power. This reduces the number go batteries we consume over a weekend during a show.
We have tried a number of methods of custom making the metal wheels to pick up power from the track, but with limited success. This is for two reasons:
- The LEGO Group did an outstanding job engineering the wheels on the 9V motors so that they are spring loaded and pick up power predominantly from the side flange contacting the inner portion of the rail.
- The choice of silver nickel has minimal corrosive issues and provides excellent electrical continuity.
Long story short, for this custom MOC train, I finally capitulated and power it with PF. A few interesting facts:
- The motor inside is a LEGO 9V PF medium sized DC motor, set 8883. The gearing to the larger steam engine wheels turns the front wheel at an appropriate gear ratio, and the connecting rod (off set on the other side by a quarter revolution) allows all three wheels to turn together. Note that the wheel configuration is flanged / blind / flanged so that the locomotive can navigate turns.
- The tender car in back holds the PF InfraRed (IR) controller as well as the battery box. I just noticed I forgot, in the photo, to put the yellow grab rails on the back of the tender car… but will add them. Oops!
- The wiring between the IR controller is done with individual wires and not a LEGO part number. The primary reason for this is the DC motor that I used was used, and the cable was broken by children using it with the wires getting twisted sharply, breaking the cable. Therefore, the motor is easy to take apart and re-wire. In doing this, one takes the PF connector end and salvages it. You wire from the DC motor to the centre pair of wires on the remaining cable of the PF connector, as these are speed regulated by the IR controller. See Philo’s page on Power Functions.
- The fun part for me is to light up the locomotive. The outer pair of wires from the PF connector have 9V all the time as long as the battery box is turned on with the green button. Then if you put four LEDs in series with a small ~50Ω resistor (three red and one white LED), at 9V you end up with the current flowing at about 7.5mA. With the train sitting still, this is well within the specifications of a AAA battery (ideal low draw for the AAA battery is about 10mA) and assuming they are about 1000mAH (milli Amp Hours), the train would last over 100 hours with just the lights on. Going back to Philo’s motor comparison page, the medium motor will use between 65mA and 300mA depending on load. Therefore, the train pulling a few rolling stock cars would run for a few hours on one set of batteries and the lights are negligible. This aligns with the club’s experience in what we see when we use PF trains at train shows.