Denver Dude wrote:I read a while back that when testing GE AC4400 units they could get down to less than 1/2 MPH at full power and the AC traction motors could take it.Full power at 1/2 mph would mean something over 2,000,000 lb of tractive effort.
Ummm.....not a chance. Knuckles on cars are rated I believe around 550-600,000lbs before they break.
So let's clear some things up. I've run coal trains with GE's on the verge of stalling. First of all, on AC motors you DO NOT modulate the throttle to control slippage. The computer does that and remember it allows a small % of slippage on purpose in the attempt for each axle to gain adhesion. The units go into what is often called "earthquake mode". What that is comes from the difference that each TM is exerting on the truck. It literally causes the engine to buck and jump and down. Those desktops aren't fully attached to the floor and they will hop up and down too....its quite a ride.
IN full throttle at those speeds, those GE's managed 200,000lbs a piece....I had two.
Harmonic rocking, as mentioned earlier, is usually to be avoided. But it usually only pertains to high cube load cars like grain cars.