• EMD SD70 series official thread (EXCEPT for ACe version)

  • Discussion of Electro-Motive locomotive products and technology, past and present. Official web site can be found here: http://www.emdiesels.com/.
Discussion of Electro-Motive locomotive products and technology, past and present. Official web site can be found here: http://www.emdiesels.com/.

Moderator: GOLDEN-ARM

  by Steve F45
dam that is a nice looking unit
  by QR National
Gentlemen...I was just looking up some things on wikipedia.com and noticed they have a large collection of info on locomotives. So I had a look at the SD70's, one of my all time favourites.

I was quite shocked to find out the first NS units were built in 1992.

Was there much of a reason behind railroads being cautious with purchasing the SD70's? 1994 saw the Burlington Northern start buying up the SD70MAC's and Santa Fe got the SD75's, along with SP's SD70's.

But major orders didn’t really kick in until the late 1990's with CSX, UP, BNSF and NS.

Thanks for any help you can give all! :-)

  by trainiac
That's happened with quite a few locomotive models--including the direct competition from GE, the Dash-9. The first five years of C44-9W production account for only about a quarter of the total produced. I think it's a matter of railroads waiting until a model has a good reputation.

In the case of the SD70 series, I think it was in part the two huge orders (BNSF's SD70MAC's and UP's SD70M's) that spurred other railroads into purchasing more for themselves.

  by USRailFan
Bryanjones wrote:These 22 units were built purposely for the EMD lease fleet.
I've heard that they were actually ordered by SP, but the order was cancelled with the UP merger, and then the locos went into EMD's lease fleet instead.

  by QR National
Thanks Michael! Quite similar to people saying how stuffed EMD would be if it wasnt for UP's SD70M order and BN/BNSF's SD70MAC order.
  by jackal
There's a switch on the rear control panel in the SD70MAC's cab that's labeled "Fresh Air Make Up Blower." It's right next to the Engr/Hlpr aux cab heater switches, so I'd assume it's related to the heating/cooling/ventilation system, but I wanted to confirm this before I get hot sitting in the cab one day and flip it on only to find the engine overheat and burn up or something. I saw it when I was deadheading back home a few days ago in the trailing unit on an overnight freight but forgot to ask someone on the crew (I'm a new brakeman).

Can't find any info anywhere on the 'Net: Google returns two results for "Fresh Air Make Up Blower" in quotes and a million unrelated ones (even with the words "EMD" or "locomotive") without quotes.

If it is for fresh air into the cab (which seems likely, especially with some human factors stuff on cab ventilation I found from the FRA), is it interconnected to the heating/ventilation system accessed through the computer control panels? Can that system be off while the fresh air make-up blower pumps fresh air into the cab separately?

While I'm on the subject, I might as well ask what some of the other non-obvious switches do. I'm sure I'll learn them when they get around to teaching me how to be a hostler, but I'm a curious person. How about the "Gen Field" switch? Seems like a generator is something you'd want to be on, but I rarely see it on, and I've been too intimidated to ask about it. Must not be what I'm thinking. Anything else I should know? :-)

Thanks! Looks like a fun forum here.

Fresh air make up blower. Fancy name for the ac/heater blower motor switch. This allows the cab climate control rotory switch to operate the heater, a/c and fan in the cab. As for the Gen Field, yes you want the gen., to run. Actually, you can't stop it.(yeah, I know, pull the fuses) This switch allows the "excited" generator to send it's current, to the traction motors. (very "readers digest" condensed version here) The loco will rev-up, but won't move. This stops the electricity being produced from actually reaching the traction motors. This, and the control switch can be off, with the engine running. The fuel pump switch will shut the loco off, when opened, after all of the fuel, between the pump and the injectors, is burned off. On another note, perhaps, since you are a "new brakeman", you might leave the operation of the loco, and the switches found on the firewall, and control stand, to the engineer........... Regards :-D

  by UPRR engineer
GOLDEN-ARM wrote:On another note, perhaps, since you are a "new brakeman", you might leave the operation of the loco, and the switches found on the firewall, and control stand, to the engineer........... Regards :-D
That aint very nice dude. You hate trainmen dont ya buddy? :-D

  by jackal
Aww, I've learned to take it in stride by now anyway.

Don't worry, GOLDEN-ARM, I won't hit the EFCO switch on you or fry something (as a almost-finished-student-pilot, I know the value of not messing around with stuff). I just better darn well know how to crank the heat up when it's -56° outside and I'm babysitting the motors while waiting for the road crew to show up.

I just wanted to know if the Fresh Air Make Up Blower is for fresh air to the cab...in case the sun's beating down and it's 104° in the cab and I'd like to try to bring in some cooler, non-recirculated air (no A/Cs on our MACs).

  by Engineer Spike
The generator field switch should only be in the up position on the lead locomotive. The one in the lead unit will trainline to the trailing units.
Some railroads want this off as a safety precaution, when trainmen are between cars. It is also supposed to be off when pumping air.

  by jackal
Ah, thanks, Engineer Spike. That makes sense. I think I'd mostly seen it down in trailing units (like the one I deadheaded in last week).

As far as the Fresh Air Make Up Blower, my engineer today said it was mostly for the computers. It was on, but I couldn't feel any air blowing out of any vents in the cabin. However, the computer fans down in the nose were noisy (as always--these are early-model SD70MACs--the newer ones are far quieter)--I didn't experiment to see if the computer fans shut off if the switch is turned off. Anyone know any more about this?

  by slchub
Hey Jackal,

If your in the trailing unit on the SD70, open up the circuit breaker panel (large door with latches on the left hand side behind the hoggers side) and the circuit breaker for the HVAC will on the bottom right hand side right above the blade switch. It may be labled heating but it controls the HVAC. If that circuit breaker is closed (meaning up and not down) then turn the heating/cooling switch above the hoggers seat to the OFF position, then back to either high cool or low cool. Some locomotives shut the HVAC off after 4-6 hours to save fuel. The fresh air make up switch will provide cooling/heating if it is off as well. Just as you were thinking, it allows for outside air to be blown into the cab, expecially useful if your deadheading in a trailing unit or in a long tunnel. Some of the GE units will have an outside air know that you push/pull behind the firemans side against the rear wall behind the cooler/seat.

Hope this helps.

  by cb&q bob
The heater/airconditioner, for the most part, recirculates the air already in the cab.
There is a small fan to the rear of the HVAC unit that draws in some outside air through a filter and then mixes it with the existing air being drawn in by the main fan in the HVAC. This small fan is called the fresh air make up blower.
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