Operating differences: Dash 9 vs. AC4400

[BDA]

Hi all , new here from Australia .

The company I work for (PN) uses mainly a derivitive of your C44-9 known as a CV40-9i and called the NR class . Next year the local franchise United (used to be United Goninan) will deliver what I think will be called the C44AC locomotives . Externally they will look similar to the NR's and use the 7FDL V16 prime mover .

I have never operated an AC traction locomotive before and I'd like to know if anyone has any manuals covering the differences operation wise whenh converting from DC to AC GE based locomotives . I think I did see something about AC locomotives not having a load meter or amp meter , rather a tractive effort meter instead .

I am really curious to see what 4000 odd Hp for traction and AC drive can do for our lower 23 metric tonne axle loads .

Cheers BDA .

[es80ac]

Do you guys use 8 axles instead of 6?

[Allen Hazen]

(ES80AC-- six axles.)

BDA--
There are already some GE AC-motored locomotives in Australia: Queensland National 5000 class. I'm not sure what they weigh*, but they are restricted to Hunter Valley coal service. If I was asked to guess, I'd guess that PN was getting simiular units for similarly restricted service... for which I think axle loading above 23tonnes is permissible.

The CV40-9i ("NR class") is very much a lightweight version of the Dash-9. It uses a smaller traction motor than the 752 that GE uses on North American locomotives with DC motors, so its low speed (continuous tractive effort/minimum continuous speed) performance isn't as good as it might be... which suggests another line of speculation!

There are manuals for some older locomotives (GE "Dash-7" and earlier) on the WWWeb, at Geroge Elwood's "Fallen Flags" rail picture site, but I think there may be legal issues about putting up current manuals. Good luck: I hope somebody can help you with this!

--

*180 tonnes, acc. to article in Aug/Sep 2005 issue (issue 41) of the Australian railfan magazine "Motive Power".

[BDA]

Last time I was stationary next to a 5000 class the look was sort of similar to an NR but with std AC4400 style bogies . I imagine to get the next lot of AC GE's down to between 134 and 142 metric tonnes (depending on fuel loading) the bogie frames would have to be pre fabbed rather than steel castings . Also I did hear that the 5000's have less fuel capacity than NR's do and this could possibly be because the AC4400 bogies are of a longer wheelbase than the prefab NR class bogies .

PN is playing with inline refueling using 20 ft "tanktainers" on the leading flat wagon though I've heard that it doesn't have enough extra capacity to run the corridor . The AC GE's on order probably exceed the allowable axle load with a full tank so the mobile gas station and an artificially low cut off point is probably the best short term answer .
Here in Aus (at least on the east coast interstate) the plan is to replace all wooden sleepers (ties) with concrete ones and when completed the operators I think will have a fair excuse to demand higher axle loads . I think 53Kg/m rail on 30 TAL sleepers could cope with greater than 22 TAL for high speed (115 km/h) service .

Cheers BDA .

[jg greenwood]

Hi all , new here from Australia .

The company I work for (PN) uses mainly a derivitive of your C44-9 known as a CV40-9i and called the NR class . Next year the local franchise United (used to be United Goninan) will deliver what I think will be called the C44AC locomotives . Externally they will look similar to the NR's and use the 7FDL V16 prime mover .

I have never operated an AC traction locomotive before and I'd like to know if anyone has any manuals covering the differences operation wise whenh converting from DC to AC GE based locomotives . I think I did see something about AC locomotives not having a load meter or amp meter , rather a tractive effort meter instead .

I am really curious to see what 4000 odd Hp for traction and AC drive can do for our lower 23 metric tonne axle loads .

Cheers BDA .

Mr. BDA,
One idiosyncrasy I discovered about the BNSF SD-70MAC's, if they're rolling back the least bit, they won't load with the reverser in the forward position, they have to be completely stopped. Not sure if this applies to all AC's though. Welcome aboard!!

[jgallaway81]

JG: The Conrail 80MACs I operated out of South Fork PA during my tenure as an Engineer Trainee had the same... flaw? I don't know if you would call it a flaw or simply an operational restriction.

[Engineer Spike]

I have had a BN 70MAC unload on me. I was starting on an uphill. I did not want to open the throttle too much, in case the rear end had not released yet. I started to roll back, and the unit unloaded. I have been told that other ac units go to full dynamic brake in this case.

[NV290]

I have had a BN 70MAC unload on me. I was starting on an uphill. I did not want to open the throttle too much, in case the rear end had not released yet. I started to roll back, and the unit unloaded. I have been told that other ac units go to full dynamic brake in this case.

I have encountered this issue on many AC units. But not all. It appears that is must be a software issue. Basically it's programmed in and can be programmed out. Because on most AC's, once you start rolling backwards, it goes to dynamic. But i had an SD70MAC (CSX) where this did not happen. Maybe something was wrong, maybe it was simply programmed differently.

The solution i have found to the issue is simply leave the independant at least halfway applied untill your actually moving forward. Ill start a train on a hill with AC's as follows...

1. With reverser in forward i go to notch 1 to make sure it starts to load, then i release the automatic.
2. As the brake pipe pressure rises, i go to notch 2 and start to gently release the independant while watching the ground out my window to make sure i am not creeping backwards.
3. So long as i have no reverse creeping, ill go one more notch and release more of the independant untill i start to roll forward. Once i am actually rolling forward, NOT Creeping, Rolling, then ill fully release the independant.

Of course, all of the above only works if your SURE your stretched out and still requires you to carefully monitor the Brake Pipe and tail end pressure. Failure to do so and being overzealous and your going to blow a knuckle or worse. My goal is to use the independant and throttle to hold the train as the brakes release and then transition to pulling once they have. This eliminates any issue with the AC's creeping backwards and then dropping the load which can become a nightmare. Especially if once they start rolling backwards you have to re-apply the trains brakes and they are not fully charged. I have heard of people getting into the perdicament and spending way too much time and energy fighting to get going. Alot of people don't understand what AC's are capable of and they are so used to DC loco's that they are scared to hurt them. AC's have no short time ratings and no brushes. Stall burns and overheating AC motors is not an issue at all. They enormous starting tractive effort and as long as they have good adhesion, you can pull almost anything. Let them do the work instead of going crazy with air "tricks" and throttle modulation to get started. Your not going to hurt anything starting a train with the independant applied. I have (for experimentation) moved a consist with 4 AC's with the indendent fully applied and from a dead stop, it was easy to get moving and stay moving. Use that to your advantage to hold a train as the brakes release on the train.

The same process works on DC units as well, however you need to be careful when using DC units (either as a complete consist or with one in your consist) as many of them have short time ratings and they can get stall burns on the motors. They are not really designed to be under load and stopped. And most have MUCH lower tractive effort then there AC brothers.