Eastern Railroad Discussion > Some Technical Questions about the CSX SD70AC Rebuilds

I was wonder how the SD70AC Rebuilds are performing on CSX especially when compared to the CM44's.

My understanding from what I have seen is that the CM44 rebuilds are cut down to the frame and have an entirely new electronic architecture with no legacy inverters or software. Since the engine outputs the same shaft horsepower I would assume you get the same performance as a Tier 4 with the exception of loading.


The SD70AC Rebuilds seem far less invasive and so I am wondering if any upgrades have been included to solve some of the deficiencies.

1. While the inverters seem to be new IGBT's which should improve maintenance and efficiency, I cannot find any information on if they have fixed the 1 inverter per truck problem. This is obviously a major factor behind their wheel slip issues and the tendency they show to jump when digging in at low speeds. So I am curious if this has been fixed.

2. Software, while all the rebuilds use EM2000 I cannot find any information on if they are running a modern OS and software suite or if they are still using the legacy system. This is another major factor in wheel slip and tractive effort performance so I am curious if this has been improved at all.

3. Traction motors/Tractive effort, The Mac has a rather low continuous output of only 137,000 klb's by modern standards. With the way the tractive effort curve works this would be due to amperage limits on the motors as well as software and overall cooling ability. I am wondering if this has been improved too.

I'm quite a fan of the locomotives overall but I am curious if the rebuilds have fixed any of their major deficiencies, they are already ballasted to 432,000 lb and do output 4300 horsepower so in theory they should be able to be pretty capable with some upgrades. The HTCR trucks are also quite a nice item to have compared to the GE ones.

All input is appreciated.

Posted from Android

Gundamator Wrote:
-------------------------------------------------------
> 1. While the inverters seem to be new IGBT's which
> should improve maintenance and efficiency, I
> cannot find any information on if they have fixed
> the 1 inverter per truck problem.

SD70MACE is individual axle control

> 2. Software, while all the rebuilds use EM2000 I
> cannot find any information on if they are running
> a modern OS and software suite or if they are
> still using the legacy system.

Units now have the FIRE control system

> 3. Traction motors/Tractive effort, The Mac has a
> rather low continuous output of only 137,000 klb's
> by modern standards. With the way the tractive
> effort curve works this would be due to amperage
> limits on the motors as well as software and
> overall cooling ability. I am wondering if this
> has been improved too.

I have not seen any new tractive effort data for the SD70MACE so don't know if there is an improvement

I would expect that the performance would be comparable to a modern SD70ACe.

Eng.Shadetree

Before I left, I had not seen any notice about a change in tonnage ratings for these motors, the 1 inverter per truck is their Achilles heel,on GE's equipped with the high tractive effort software, I would put one screen to the locomotive monitor, you could watch it shift loading among the six motors based on traction and in most hard pull situations, loading increased per traction motor as you went from one to six as each successive wheel set conditioned the rail,something the 70MAC's could not do, extra weight and all, probably the biggest addition is DP giving power planners more flexibility.

Posted from Android

alamode Wrote:
-------------------------------------------------------
>
> I have not seen any new tractive effort data for
> the SD70MACE so don't know if there is an
> improvement

Still the same tonnage rating everywhere I can see, I don't think Tractive Effort was changed at all. 

Messicrafter Wrote:
-------------------------------------------------------
> alamode Wrote:
> --------------------------------------------------
> -----
> >
> > I have not seen any new tractive effort data
> for
> > the SD70MACE so don't know if there is an
> > improvement
>
> Still the same tonnage rating everywhere I can
> see, I don't think Tractive Effort was changed at
> all. 

And they still have desktop controls which I hate....