Using portholes can be an advantage in sealing the opening. Likely explaining their origin in boats/ships. I don't see this as being a big problem in railroad rolling stock. But it could certainly be a consideration.
Also, as has been mentioned, a round hole is advantageous over a square hole; but only in a stressed skin. Like a typical steel boxcar side. EMD E's and F's did not have a stressed skin.
Beyond that, there is the matter of styling. I think it likely that portholes showed up on railroads in the '30's. As did the architectural term "Streamline Moderne". From the Wikipedia page on the subject, some characteristics were:
Rounded edges
Porthole windows
Of course, buildings don't NEED streamlining (as in aerodynamics). But they do go hand in hand with taste in styling. Railroad rolling stock, however, does have potential advantage in aerodynamic streamlining. And one of the characterics is curves, rather than straight lines (see also "rounded edges", above). And you can't get much more rounded than a circle.
So I suspect the use of portholes in rolling stock was primarily styling; styling which also tended to be reinforced with the real advantages of aerodynamic streamlining.
Ed
Interesting thoughts, Tom.
I see that with the spacing on the FT, two of the portholes are bisected by frame members. Now that seems to be an engineering head-scratcher. Corrected on the F2 and beyond.
Any light available in the engine room is good especially if the engine is dead and no battery power is available for engine room lights.
I wonder if one of the reasons for a round window was stress relief and easier sealing. The early EA up through the E7 had rectangular windows.
The hinged windows, as you point out, would make for easier access to pass tools or test cables through. I remember seeing locomotives being load tested at Collinwood but I do not recall how the resistor cables were connected. Presumably into the high-voltage cabinet which would make passing the cables through the porthole opening more logical.
B units of course had a hinged opening for the hostler to poke his head outside for "navigation".
One of the reasons for elimination of the portholes in later years (mid-1970s) was the FRA requirement to have extremely break resistant "ballistic" glazing on locomotives. Rather than make the modification, it was cheaper to simply plate them over, same with windows on cabooses.
The side louvers had filter media behind them and some were ducted to the traction motor blower and others to the engine intake air.
Fun Stuff,
What was the purpose of the portholes on EMD E- & F-units?
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To allow air and light inside during maintenance. The motor area of a cab unit was dark,smelly and hot. The mechanics would open all the doors and the portholes to get fresh air..Plus one near the end on a B unit next to the contril stand was used by the hoster if he had to move a B unit. He would stick his head out the porthole as he moved the B unit.
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Why the various configurations?
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Different models and production phases. Let's use EMD as a example. EMD would get feed back from the railroads and would make changes according to the railroads observation based on serveral things including employee complaints.
Larry
Conductor.
Summerset Ry.
"Stay Alert, Don't get hurt Safety First!"
Portholes were the style the F-units and E units had in the 1940's/1950's.
The T1 Duplex also had portal...ettes on the sides of its lower front pilot cowling.
Cars also had portholes in those days. The early T-Birds come to mind. I guess designers got kinda fixated on them.
Robert
LINK to SNSR Blog
This thread titled "Why Portholes", on a different forum, has some interesting discussion and history.The thread does point out other manufacturers (ALCO) and types of equipment had portholes (such as the famous PPR N5c caboose...er, cabin car).
This may have been asked here before but could not find it using the MR search engine and Google wasn't much help either:
FTs had four concentrated in the middle area. The F2s had three that were evenly spaced. The F3s/F7s/F9s had only 2 near the ladders; the middle porthole apparently replaced by square openings covered with metal screening. E-units had their own variety.
I presume the portholes allowed for ambient lighting in the engine compartment and the screened square openings allowed for some additional lighting and/or ventilation? I also presume that the port holes could be opened and perhaps used for communicating to the outside during maintenance operations - especially if the engine was running.
Am I close? Or am I just making stabs in the dark?
Thanks,
Tom
https://tstage9.wixsite.com/nyc-modeling
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