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[CBQ] Re: compatibility of engines

To: <CBQ@yahoogroups.com>
Subject: [CBQ] Re: compatibility of engines
From: <qrailroadman@yahoo.com>
Date: 19 Feb 2014 13:55:42 -0800
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Re: compatibility of engines 
 When running units of different makes and ages, when electrical connections 
match, the MOST important factor an Engineer must consider while moving over 
the road is the SHORT TIME RATING of the unite in his consist.  A rule of thumb 
says that older units generally have shorter time/amperage limits imposed on 
the motors.  If you have an F7 in the lead, coupled to an F45, which I have 
had, there's NO problem !!  The limiting factor in this example is the short 
time rating of the F7.  Since I'm ON the F7 all I need to consider is the 
ammeter which indicates the length of time the motors can safely absorb any 
given current level.  Now, let's put the F45 in the lead, as I have also had.  
Since the 45 can sustain substantially higher motor current loads than the 
older unit I can't use its ammeter to regulate the load  necessary to protect 
the F7, I must be aware of the ratings of the older unit and avoid the speed 
and throttle position conditions that would generate damaging current levels in 
the older unit.
 

---In CBQ@yahoogroups.com, <runextra@...> wrote:

 > As I recall, an SD45 only had one step of transition, while the SD7s and 9s 
 > had three. Early SD45s also had shunting steps

 Yeh, the early SD45s had 6 different shunt conditions in series-parallel and 4 
steps of shunt in parallel! Parallel shunts could go to the same 6  steps as 
series-parallel _IF_ the engineer was brave enough :-)
Now count both forward transition & shunt steps plus reverse transition and 
shunt steps and that is a lot of detecting and relays clacking!

Around the Sheridan/Gillette, WY area in the 1970-1980s low speed loading of 
coal trains before computers required locos equipped to lead and trail a 
"Pacesetter" box. This was a separate easily removable metal box maybe 9x9x5 
inches that mounted on top of the control stand and had 2 screw-on cables that 
connected to the back of it. Flipping a switch on the lead loco to Pacesetter 
Operation caused the main generators/alternators fields on all units to respond 
to a varying voltage control signal on an "optional" MU cable wire. That signal 
was supplied by the Pacesetter box and it varied according to loco speed. The 
Pacesetter could control speed to within less than 1/10th of a MPH.  Loading 
coal at 0.25mph was not unusual.  The pacesetter had various knobs to set the 
speed and a meter to show the loco was operating at the set speed. 

Some times you'd get a unit that was not equipped for pacesetter operation. 
These units would continue to load normally and had to be isolated while 
loading coal. MILW units and others  were like that. If it was the lead unit 
then you had to go back to a pacesetter equipped trailing unit and load coal 
from there.

One night I got an officer special out of Billings, MT to Sheridan. It had a 
new SD40-2 and a new GE C30-7 for power. The first car of the train was a power 
car for lights & heat. The carmen plugged in the MU cable between the 2nd loco 
and the power car. Unbeknownst to anyone on the train crew or the RFE that act 
set up the GE to trail a pacesetter. Apparently a conficting use of the same  
"optional" MU wire.  After departure I soon realized I only had one loco 
operating. I could not maintain the Train Order schedule with the 18 car 
passenger train. So when we arrived at Sheridan 2  helper units were added to 
the point for the trip to Gillette. The problem was finally figured out at 
Alliance or Lincoln. The MU wire that set up trailing units for Pacesetter 
operation was apparently the same wire that was used on passenger locos to 
control the steam generators on trailing units. Those locos had toggle switches 
and lights in front of the fireman's seat for that purpose. So when the carmen 
had plugged in the MU cable between the freight units and the heater car the 
heater car screwed things up on the trailing GE. 
So you see, even in modern times there are occasionally problems with 
incompatible MU wiring.

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