I’ve seen all sortsof pics of head end mixes but I’m wondering if there are any simple clear rules for what can be mixed with what. Clearly a lash up will have to have MU connections - but so long as the locos have those what affects the mix or the order of the mix please?
Thanks [8D]
Some roads (like Canadian Pacific) didn’t have proper MU connections on the noses of F-units, so those could only be first or last in a consist.
Small switchers that were specifically purchased for yard switching sometimes didn’t have any MU connections at all, and in the earlier days different manufacturers had different connections. This later quickly become pretty standardized, but IIRC (and someone can correct me on this) certain builders like Baldwin still used a completely different system for a while so couldn’t be run with any other builder.
Generally if their gearing ratios were the same (or close to the same) you could run any two engines or more together that had compatible m.u. connections. Diesels are/were set-up with different gear ratios for different purposes, so that your railroad’s passenger diesels could all go say 80-90 MPH at top speed, whereas general freight engines would be geared to top out at say 60 MPH and switchers maybe at 40. So running say an E-8 and a PA together usually would be OK. Of course some railroads had GPs or RS-3s that were set up for passenger running, so it can be hard to tell what is a passenger engine and what is a freight engine sometimes.
If you go way back into the 1950’s, 1960’s etc, there were some roads that used a different MU cable pin arrangement so their units might not MU with units from other railroads (I think the UP may have had a different or early configuration).
Some Baldwins had air operated throttles so they might MU but only with other Baldwins.
There are other considerations such as dynamic brakes, AC traction motors, gear ratios, non-alignment drawbars, etc. that affect the order the engines have to be in the consist and how the train is handled but they don’t affect the ability to MU.
You will want a unit with dynamic brakes, and the highest minimum continuous speed in the lead (plus comfort cab, air conditioning, ditch lights, TIR, DP control, cab signals, yadda, yadda).
Some RRs had specific rules on the lead engine based on how much time the engine had since the last service. A “fresher” loco would be placed in the lead. I can’t recall the exact term for this as it’s been some time since I’ve seen a discussion on the subject.
Other reasons may be that locos may be equipped with cab signals and they would have to be in the lead for sections of the RR that require them.
Ricky
Looking from a pure operating stand point, as long as all units in the consist have MU capabilities and the MU connectors used the same (hense a set standard) they will work. Thinking specifically of GP units, there is a dead cock used to basically shut off air to the brake controls, the throttle is left in idle, the selector leeft in neutral, a switch denoting which number unit it is in the consist, and a switch that is turned to denote which end of the loco is pointing forward. Ifreally interested look online for OP ,manuals. I have several of them for my favorite diesels including GP/SD9, GP30, RS3, GE 44T, U25B, GP38, SD24, and just about every model Alco. I kinda have an unexplainable attraction to Alco’s.