I have an oval in my office where I run an N scale train. I have 27 cars and 2 identical Bachmann GP40 locos running back to back. It's been running mostly fine for a while but today the lead loco started stalling and spinning its wheels when it came to one curved section of the flat track. So I know it isn't an electrical problem. I turn the power up and it just spins faster. I cleaned the wheels of the locos and it doesn't make a difference. The track is all the same, so not sure why it's picking this particular section to have issues. So I switched the position of the two locos and it is running fine again. So my question is, why did the lead loco start spinning its wheels and why did this resolve itself when I switched the positions of the two locos? As both locos are identical and the track is all the same, shouldn't the behavior of both locos be identical no matter which one is in the lead position? Thanks.
Loco spinning its wheels
- Thread starter RickVS
- Start date
Selector
Well-Known Member
Has the plated surface of the formerly lead engine's tires changed noticeably? Maybe the coating has worn sufficiently that the traction has suffered just enough to cause the locomotive to spin.
Also, I don't buy that the tracks haven't changed. At the very least they have worn about as much as the tires under the locomotives. But also, over time, EVERYTHING is fluid. Everything 'runs', or sags, or deforms, over time. Even daily or seasonal changes in ambient temps and humidity will affect our wooden supporting structures on our layouts. It's why I run a dehumidifier in my train room year-round. It may go several weeks without cycling into the drying process, but it's always on, ready to cycle and to commence the process. Some times I go into the train room to find the red light illuminated and the machine silent, indicating I need to empty the now-full reservoir. I had no indication that the humidity had changed and that the machine had been working for some time.
One other possibility, but I'm at a loss to explain exactly how the physics would work: maybe the drive mechanism of that former lead locomotive has finally broken in such that the drive is capable of delivering more tractive effort with the same amount of voltage, and drawing the same amperage. It has gotten to the point where it wants to spin where it couldn't before, and now you're seeing a 'freed' mechanism that wants to go faster, or to pull more, than you had it set for when it was matched with the consist. If you could couple each locomotive separately to a heavy consist and measure its amperage draw at a defined voltage, say 8 volts, and repeated the test with the other locomotive pulling the same consist in the very same location on your layout, also 8 volts, you might find a difference in either tractive effort or amperage. Trouble is, you'd have to be able to compare those figures with a previous test to really see if my suspicion is right.
Also, I don't buy that the tracks haven't changed. At the very least they have worn about as much as the tires under the locomotives. But also, over time, EVERYTHING is fluid. Everything 'runs', or sags, or deforms, over time. Even daily or seasonal changes in ambient temps and humidity will affect our wooden supporting structures on our layouts. It's why I run a dehumidifier in my train room year-round. It may go several weeks without cycling into the drying process, but it's always on, ready to cycle and to commence the process. Some times I go into the train room to find the red light illuminated and the machine silent, indicating I need to empty the now-full reservoir. I had no indication that the humidity had changed and that the machine had been working for some time.
One other possibility, but I'm at a loss to explain exactly how the physics would work: maybe the drive mechanism of that former lead locomotive has finally broken in such that the drive is capable of delivering more tractive effort with the same amount of voltage, and drawing the same amperage. It has gotten to the point where it wants to spin where it couldn't before, and now you're seeing a 'freed' mechanism that wants to go faster, or to pull more, than you had it set for when it was matched with the consist. If you could couple each locomotive separately to a heavy consist and measure its amperage draw at a defined voltage, say 8 volts, and repeated the test with the other locomotive pulling the same consist in the very same location on your layout, also 8 volts, you might find a difference in either tractive effort or amperage. Trouble is, you'd have to be able to compare those figures with a previous test to really see if my suspicion is right.
D&J RailRoad
Professor of HO
Where the wheels of the second loco actually turning too?
These locos are only a couple of months old, so I can't see that there would be wear or technical issues with them.
If it were a simple traction problem, then wouldn't it make sense that that engine would have similarly poor performance on curves around the track and not just in one area? I would add that it does at times hesitate at different areas of the track but it doesn't stall at those places.
I think what Ken was meaning is. Are the wheels of the rear loco rotating, because if they are stopped while the front ones are spinning, there's your problem. The front one with the spinning wheels are trying to drag a non operating loco, acting like a brake + the weight of the train and slipping. Reversing the locos end for end will put the non turning wheeled one in front of the operating one and reduce the load on that one, allowing it to be pushed instead of pulled.
Selector
Well-Known Member
Only if the factors were the same in all instances. They almost certainly are not. Nobody crafts curves, or tangents, that are perfectly level, or where the rails are level across from each other, transversely, and nobody lays perfect radius curves. Benchwork undulates and makes the rails they support lie at slight grades, or perhaps the roadbed does.
