What determines the amount of power/tractive effort of a slug unit. Is it based upon the type of mother, such as, will a slug tied to a GP40 be stronger than a slug tied to a GP38? I understand that the some of the mothers power goes to the slug, is it an all together alternate path, like some new locomotives bought by ARR, which unplug two traction motors in order to provide HEP (this was mentioned in a recent thread), or is the power supplu in a parallel path, and all the motors of the mother work, and it has a lower amperage rating for each one?
About what is the power split? 50/50, or perhaps 66/33?
One more thing, in some yard photos elsewhere on this site, there were shots of a slug between two mothers (mother and father, for extra conservative people) , or at least a mother and a regular cab unit. would the slug in the middle draw power from each unit, and raise the entire speed rating, or would one cab unit be separate, with the other the only mother?
While I’m not an engineer, I will try to provide an opening statement in reply. Slugs do not provide any additional horsepower to their lash-up. A GP40/slug set still has only 3000 HP input into the main generator. A slug’s additional weight and traction motors do provide additional low-speed tractive effort by changing where the tractive effort curve is cut off by the limits of adhesion.
Slugs can be wired to draw electrical power from the mother unit(s) in a variety of ways. An article in TRAINS in the late 70’s-early 80’s goes into good detail about this matter.
You would genearlly design the slug to have the same TE as the mother. It would have the same traction motors, gearing and weight. A slug has zero HP. In use the mother and the slug share the power from the mother equally.
With the slug on line, you double the TE at half the speed. So, if a GP40 mother alone has a min cont speed of 20 mph, and produces 50,000# TE, the mother slug combo will have a min cont speed of 10 mph and produce 100,000# TE.
Since the mother and slug are in series, your top speed is voltage limited to 1/2 the normal top speed. For a GP40, it would be about 35 mph. It is possible to cut the slug out on the fly. CSX does this by 100% shunting or the TM fields on the slug. The current still goes thru the brushes and armature on the slug (this keeps the commutator happy) but (almost) no power is consumed.
Since the mother and slug are in series, your top speed is voltage limited to 1/2 the normal top speed. For a GP40, it would be about 35 mph. It is possible to cut the slug out on the fly. CSX does this by 100% shunting or the TM fields on the slug. The current still goes thru the brushes and armature on the slug (this keeps the commutator happy) but (almost) no power is consumed.
Are any of the railroads hiring commutators about now. Sounds like a cushy job!