I have a question regarding the pulling power of N Scale Locos in general and one specific to a new Bachmann SD-45. Coming from the 3-rail O gauge world I'm used to engines with enormous pulling power even with ridiculously steep grades of 4% or more. One loco pulling 15 -20 cars up a 6" rise in 12 ft of track has never been a problem. On my door size N Scale layout I was careful to keep the grades to no more than 2% yet I find the SD-45 slipping in a climb while pulling just 7 cars; a mix of 4 box cars, a tank car, hopper and caboose. Six cars- no problem, but adding one more causes it to start slipping. So what's the deal? The Bachmann SD-45 doesn't have any traction tires. Is that the problem, or is there some other problem with that particular loco I need to troubleshoot? Or are ALL N-Scale locos just "weaker" than what I've been used to and I'll need to get another engine to help if I want to have a consist of 12 cars or so? Up until I added the 7th car the SD-45 was running very smoothly. With the sound turned off the motor is practically silent with the only noise being the sound of the wheels on the rails. Finally, if I get another loco should it be another SD-45 so that when I program it into the consist they'll have matching pulling power or can I look for another type?