John,
The air compressors were direct drive from each engine. They were
located in line with the engine crankshaft as were most EMD
locomotives until recently when they went to electric air compressor
drives. If you look on page 40 of Burlington Bulletin #10, an
interior layout drawing of the E-7, and all the other E units for
that matter, is shown. While not identified as such, the air
compressors are shown toward the rear end of the locomotive on each
engine.
On EMD locomotives, the front end of the diesel engine is the
governor end while the rear is the main generator end. As an
interesting side note concerning the E units, with the change from
the E-7 to the E-8, EMD changed the orientation of the engines. On
the E-7, both generators are located toward the front of the
locomotive. On the E-8 and E-9s, the front engine has the generator
toward the front of the locomotive while the rear engine is located
with the generator toward the rear. This allowed easy access to the
engine controls and adjustments via the center carbody door, which
was moved forward on the E-8s and 9s.
As for the air inlet panel behind the cab doors, it probably provided
additional air for the equipment within the carbody. Judging by the
photos in the Burlington Bulletin, it was a shuttered assembly, not a
fixed louver assembly. Note that the shutters are closed on some
locomotives while they are open on others. Because it was adjustable,
it suggests that it was intended for temperature control. Whether it
was automatically or manually controlled, I don't know. Maybe some
"old heads" who worked on E-7s can answer that question. In all
likelihood, they were intended to allow more cool outside air into
the carbody in hot weather and close it off in cooler weather. It
definitely wasn't for cab ventilation as that wasn't a concern in
those days! The only ventilation in the cab of an E unit was roll
down windows, just as on automobiles of the day. Based on the
interior drawing in the Bulletin, the only equipment near the shutter
assemblies appear to be the oil filter housings. The oil coolers were
located in the water make up tanks.
Why some of the air inlets were blanked off is certainly unclear. The
Burlington Bulletin even suggests that more left side assemblies were
blanked off than those on the right side. Possibly, it was determined
that all of the additional air wasn't needed. Some units, with and
without the shutter assemblies, had an additional air inlet filter
added below the rear air inlet along the roof line. E-8s and 9s,
which had similar carbodies, did not have the shutter assemblies. By
the way, it appears that the assembly was a door. If you look at the
photo of #9921B at the bottom of page #14, it is possible to make out
three hinges on the cab door side of the assembly. If, in fact, the
oil filter assembly was located just inside that area, the door
function may have been provided to remove the very messy oil filter
elements without having to carry them through the carbody. Each
element is about 4 feet long and six inches in diameter.
Bill Barber
On Jul 31, 2008, at 4:07 PM, CBQ@yahoogroups.com wrote:
> Re: E7 airfilter doors
> Posted by: "John Trulson" norskeviking@msn.com
> Wed Jul 30, 2008 9:23 pm (PDT)
>
> I always thought the air compressor was behind those doors and
> that's why they were either louvered or screens to draw in air to
> keep it cool. Just a thought. John
[Non-text portions of this message have been removed]
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