Well, a slug is used when the prime mover it is attached to generates more electricity than can be used by the motors of the main unit. This is almost always very low speed applications. So I would say if your unit is ever going to get over 15-20 mph you want a B unit. If it is always under 15-20 mph it would be a slug.What I was thinking for this one, is that's it's to be used in one of Milwaukee & Western's subsidiaries iron ore traffic, helper service and for switching at the docks. What I can't decide, is if I should turn this unit, which will be an RSD 4/5, into a slug or a B unit, which would be better for railroad and this kinda operation, suggestions, ideas?
With iron ore traffic a rather heavy business, I'm kinda leaning towards the B unit idea...

......at the moment, the Milwaukee & Western are the proud owners of:
5 Alco RS3,
4 Alco RS11,
4 Alco RSD4/5,
1 Alco RSC2,
1 Alco RS1,
2 EMD SD7,
1 EMD SD9,
1 BARF,
1 Baldwin VO-1000....
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