Yes, the engine overspeed lever will shut down the motor if it starts running too fast. That can happen a few different ways, but really has nothing to do with how fast the actual locomotive is traveling - although getting wheelslip in Notch 8 at a high speed can cause the engine to overrev, how or why I dunno, but thats what I was told.
There are overspeeds that are built into the cab signal system which will put the train into a penalty brake application if the speed gets too much. For example, on the Geeps that NJT runs, their overspeed is set at 103mph (give or take a few mph) which is the limit of the traction motors and whatever gearing that is, i dont remember off hand. If you hit that, the cab signals will start beeping and you have to get brakes on, and get your speed down, otherwise it will put you into a penalty brake.
Let me just say that you haven't lived til traveling down the NEC long hood forward in a Geep at 100mph..........Not quite what the designers at EMD had in mind 50 years ago when they were designing the '40 series, im sure.....hahahah
But like a quite heated discussion that was going on in the loconotes group on yahoo a few weeks back, a locos power does not necessarly equal how fast it can go. Like I mentioned, a 3000HP GP40 can go 100mph. A 4300HP SD70 might only be able to go 70mph. A 1500HP switcher might be able to go 70mph. It all depends on the gearing of the traction motors. Power does help, with how fast it can get to a certain speed, but by no means is it the only factor.
Now, take for example a 103mph geared GP40-2 and a 70mph geared GP40-2. Couple up say 10 100ton loaded stone hoppers to both of them. Put them next to each other on two tracks, and let them drag race. The 70mph Geep will take off like a bat out of hell (relatively speaking) and have no problem pulling the cars and getting up to 70mph. The 103mph Geep will take off slower and will struggle more with the cars to get them up to speed, but it can move them no problem. It will take a while, but it will be able to get them to 103 mph.
At NJT there is an unoffical limit with how many loaded stone hoppers a Geep is good for, which is about 10. A freight guy will be like "10 cars with a GP40? Thats nuts! These engines suck!" They don't suck, they have the same power as a freight GP40, but just gets it delievered differently because of the very high speed gearing
On the RR, "believe nothing you hear and only half of what you see"
John, aka "JTGSHU" passed away on August 26, 2013. We honor his memory and his devotion to railroading at railroad.net.