Clinchfield F7 Often Loosing Power Shortly. Why?

While driving the F7 uphill, but with the Amps still in the green zone, I find my F7 often loosing power shortly. Amps suddenly drop to 0, and then slowly ramp up again. I see no indication of wheel slip. What's happening, and what am I doing wrong?

 

You’re not doing anything wrong, it’s the loco doing a transition. It either cuts in resistors or switches the traction motor wiring between series and parallel to allow higher amps at higher speed.

An explanation of this can be found in this F3 manual (page 32 of the pdf and onwards) since it still had manual transition while the F7 does it automatically.

 

And here F-7 Operator's Manual - F7-0-651 (rr-fallenflags.org)

 

Exactly. It's equivalent to your car's automatic transmission shifting gears.

 

I started driving the F7 at the weekend and I lost hours and hours to the Clinchfield route. I don't usually enjoy American freight but this route has me hooked, I love it. I thought there was a bug with the F7 as I noticed the amps randomly dropping to zero, I was thinking maybe I was driving it too hard and it was auto cutting out but I always keeps the amps in the green. This is great to know, but this route really needs a manual.

 

Actually,all routes need a manual, as all the different trains have their own little quirks, and more important to explain the signal along the tracks, not just the lights but all the little signs that are found on the side of the track

 

The 66 does the same at 34mph.

 

All diesel-electrics do it. Any of the NTP and TVL diesels show the same behavior (except the 101, natch)

 

I drive the class 40, 45 and 47 alot on NTP and I've never seen the amps drop to zero like the F7 does. I do notice when they cut through different field diverts and the amps jump and it's very noticeable on the Class 31 but again, nothing like what the F7 does.

 

Just a difference in the way the system is implemented. The EMD way was to momentarily disconnect the traction motors to avoid "dumping the clutch" and redlining. Whereas on British diesels, each transition step results in an amperage surge which forces you in most cases to throttle down.

 

I don't think the Geeps do.

 

I actually experiencing the same thing when driving CSX GP38-2 on Sand Patch Grade, when passing Notch 5 (or 6), the power briefly cut-out and slowly begin to creep up again. Perhaps it is a thing on older diesel-electric locomotive since i never experienced the same thing on AC44CW, SD70ACe nor the ES44AC.

 

Newer D/Es use traction inverters which obviate the need for transitioning

 

Is it linked to overloading and wheel slip?

 

Nope, it’s linked to what all the above replies indicate, which is normal transitioning behaviour of the locos.

 

This also happens to SD40 CSX-S Clinchfield versions too. In some cases if you are going downhill be prepared to take control of AC4400CW if hill start is required