From: guy@boi.hp.com ()
Subject: Re: Tunnel Motors
Date: Wed, 16 Dec 1992 18:15:17 GMT
Organization: Hewlett-Packard / Boise, Idaho
X-Newsreader: TIN [version 1.1.2 PL7]

In his followup 737ochs@gw.wmich.edu (737ochs@gw.wmich.edu) wrote:

: Actually as far as I know, that isn't the theory behind Tunnel Motors.
: The theory of them is to take in air below the normal place. Normally,
: EMD's take the air in at the to of the hood and blow it out the roof.
: In tunnels, they take in the hot air they just blew out. So they reconfigured
: the cooling system to take in air at the bottom, and also made the fan one
: large fan instead of 3. It has more of a GE look to it, without the wings.
: EMD has used this desing on engines other than the SD40 and 45's
: They also put them on the GP15-1 and GP15T (T here stands for turbocharged)
: and also on the MP15,MP15AC, MP15DC and MP15T (again T stands for turbo)
: 
From working on the TE70-4S Sulzer units for Southern Pacific a few points 
stick in my memory.

1) Tunnel motors actually have three fans in the back just like regular
units.  They are placed under the radiator cores in this configuration
intead of above.  They are the same fans just bolted to slide out plates
instead of to the roof.  That's what the little horizontal doors are for
just above the intake screens in the back.  The improvement in cooling
came from the lower intake position and consequent cooler air.  This
advantage gradually diminishes as you get further into the tunnel.
Basically, T2s lasted longer before they over heated than conventional
units.  Usually, they lasted long enough to clear the tunnel.  SD45-T2's 
used 8 row radiator cores instead of the 6 row of the SD45-2 cooling system.  
However, the "push" position of the fans is less efficient than "pull"
due to uneven velocity distribution across the radiator.  The net was a
decrease in cooling efficiency of the package!  

2) Usually, the first unit in consist is OK through the tunnel
but not always depending on speed and wind condition.  Helpers (manned
on the SP) see high temperatures and pretty foul air.  Studies showed
air temperatures at the radiator intake on standard EMD units of 280
deg.F on the fourth unit of the lead consist.  Hard to cool the water
with that kind of air.  Temp at walkway level was about 140 degF. as I
recall.  I got caught out on the third unit in a short tunnel while I was
taking some engine readings.  It was VERY unpleasant!

3) Engine air intake was left in the normal position with the result
that trailing units injested very foul air.  Various derating mechanisms
in the governor, etc. caused the horsepower to back way off.  In summer,
the third and fourth units would derate from 3600 to around 1600 HP exiting 
the tunnel.  This makes for a nervous time watchhing the speedometer creep
down and the ammeter creep up on the lead unit.  If the train stalls,
the tunnel will quickly become uninhabitable even on the lead unit.

4) Worst point on SP for max. temperatures was on Donner between Reno,
NV and Roseville, CA due to long tunnels.  Worst point for locomotive 
performance in general was actually in the Cascades east of Eugene, OR due 
to numerous short but back to back tunnels.  The units just never had time 
to recover from one to the next.

5) Units without cabs (B units) seemed to be a real problem for
the dispatchers, etc.  I think they didn't want to deal with it for the
relatively small cost savings (around 5% of unit cost).

-------------------------------------------------------------------
Guy Burnham  Boise Surface Mount Center, Hewlett Packard Co. Inc
guy@mrtrain.boi.hp.com
Disclaimer: My opinions are strictly my own and ........ (you know the rest)
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