Last Christmas I built an extended Emerald Night train to run around the tree. To get it to work I had to add a second Power Functions motor. I tuned both IR receivers to the same frequency and slowly applied power by keeping the IR remote within the line of sight of both receivers at the front and the back. The major disadvantage to this was it was difficult to sync the two engines because line of sight was not assured.
I'd like to build a larger train this year and would like to find a better way to link the motors. I've think that putting one motor in the back helps with weight distribution, although this idea may be flawed.
What the best way to link multiple Power Functions motors together without having to rely on multiple IR receivers?
Below are some photos that provide more detail about the train in question.
Front engine, standard Emerald Night (10194-1):
Rear power car, custom (MOC):