So far I have created the rumble of the cart and have squeaks of the wheels on the track. It's the electric whir of the motor that is giving me trouble. I need the sound to be versatile as the trolley makes frequent stops. With every source file I seem to run into the same problem, the sound turns into white noise. I've tried using recordings of a drill and a jig saw, I went to new orleans and recorded the trolley, I've tried using recording of motors from soundcloud and I always end up with a result that sounds more like an airplane than the trolley motor. Here's a video for reference http://www.youtube.com/watch?v=DtHROGTHiSk&feature=relmfu . If anyone has suggestions please let me know, thanks!
Ok I just tried something and it worked almost exactly for what you need. What popped into my head first was that the "motor" sounds kind of like a mid frequency drone, almost like a stringed instrument changing in pitch. I opened up iris, loaded the violin sample, found a neutral sounding note and slowly modulated the pitch up and down. If you have a midi keyboard and some kind of sampler try this out. This will also let you perform the sound to picture for a better result.
I would layer or create some kind of sound that is not exactly a violin, but that sounds closer to that electronic hum/ whine. When you find a sound you like, layered in with the rattles, bells and other ambiences it should work out nicely.
I would start by looking at underground trains like London's tube. The trains on the tube are slightly more modern, but if you pitch shift them down a little I think they will work once you add all of the street and track rumble.