SD90MAC-H - what went wrong?

[Anonymous]

Exactly what caused the SD90MAC-H to be a (relative) failure? The answers I've seen have been "Too powerful" and "unreliable". The former can't be argued with, certainly not many railroads/tasks could use that power, but why was it unreliable? What was to blame - was it produced without sufficient testing / bug fixing, and if so, who put the pressure on?

[kenneo]

It was an expimental engine to begin with. EMD couldn't get it engineered quickly enough to meet Tier II deadlines (one of the reasons it was made), so most (if not all) H engines produced were replaced with 710's and the locomotive derated. A lot of SD90/43's were made, and this is essentially what the conversions became.

Look for the H engine to be back, because it will be back. Just when, we don't have a clue. The Tier II 710's are now doing everything the railroads want them to so there is no real rush for the H.

[Anonymous]

[:)][:)][:)] It helps sale a lot if you can keep the motors in one big chunk and turning without parts breaking or coming out the sides and oil pan.

[Anonymous]

So the pressure to "get it out the door" was partly the environmental regs?

[K. P. Harrier]

My recollection is that Union Pacific’s previous administration pressured EMD for a quick 6000 HP unit.

If true, the old saying proved true again: Haste makes waste.

[M636C]

Remember that GE was also producing a 6000HP locomotive, and they had a design that had already been built, with fewer cylinders, by Deutz in Germany. I understand that EMD were planning to build the H engine as a smaller engine (I'm told they were planning a V-16 with 854 cubic inches per cylinder giving 5000HP total, but had to enlarge it to more than 1000 cubic inches per cylinder to match GE's engine).

EMD's engine was more ambitious than the GE, as well and had been laid out with a "cross flow head", the inlet air entering on the opposite side to the exhaust. In a vee engine, this meant from the outside. EMD also tried to improve the intercooling by mounting the intercooler in place along the side of the block. This had not been tried before on diesel engines to my knowledge, although ducts from an intercooler at the end of the block have been commonly used.

These differences from standard and the late change in cylinder size all increased the pressure on EMD and the H engine. The fact that the 710 G3B was doing very well and that GE also gave up on the 6000HP locomotive meant that EMD could concentrate on the two stroke solution, and ironically, this gave them an advantage over GE in the current 4400 HP market. But the H engine may be reintroduced, just as GE may build a 16 cylinder GEVO if the demand arises,

Peter

[adrianspeeder]

Like an all nighter before a deadline, maybe some things got missed in R&D.

Adrianspeeder

[edbenton]

Another reason also could be the fact that the 90MAc and the AC6000w were designed to power high speed piggybacks on their own but not if but when they failed it tied up the whole main line.