# 1st or 2nd gen. hood units



## bgoatsw (Apr 16, 2012)

Could some please explain the difference from 1st generation hood units to 2nd generation hood units for locomotives, like what units this pertains to and manufacturers. Thanks G


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## cv_acr (Oct 28, 2011)

"First generation" roughly refers to the early diesels that replaced steam engines.
For example, 
EMD up to 20-series (all F-units, SW switchers, GP/SD7, GP/SD9, GP18, GP20, etc.)*
Alco PA-1, FA-series, S-series switchers, RS-series, etc.

*Exception: the GP15T/GP15-1 was a much later second-generation unit built in the late 1970s. The BL20-2 is also a 2nd-gen unit. Generally though the lower numbered EMD models were 1st-gen designs.

"Second generation" roughly refers to the diesels that starting displacing the original units to lesser duties. Second generation units are often turbocharged (but not always - e.g. GP38), and there's a distinct shift in body styling between first and second generation units.
For example:
EMD 30-60 series (GP30, GP/SD35, GP/SD38, GP/SD40, GP/SD50, GP/SD60, etc. (and -2 variants))
Alco Century-series (C420, C630, etc.)
GE U-series (U25B, U30C, etc.)

Today's big high-horsepower units could be considered third-generation (especially units built or rebuilt for modern emissions standards).
For example:
EMD 70+ series (SD80MAC, SD90MAC, SD70ACe, etc.)
GE C44-9W, ES44AC, etc.

Gen-set and battery-powered "Green Goat" switchers might also be considered third-generation.


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## cv_acr (Oct 28, 2011)

The line between 2nd and 3rd generation is a little fuzzy, but there's a distinct different in styling between the 1940s-1950s 1st generation and 1960s+ 2nd generation units.


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## Pfunmo (Feb 21, 2013)

It's not a firm line and there can be all kinds of different varieties that fit in between. Kind of like definitions of generations of people? Some people may call it depending on the age of the engine but then some lasted well into the next generation by having modifications made. Is a GP-7 still a first generation if it has been shopped and had massive modifications made? Not something I've ever given too much thoughts as there really is no definite answer other than what is mentioned above for general guidance. Some will favor hard and fast rules while others are not too concerned.


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## tjcruiser (Jan 10, 2010)

Excellent summary posts above, CV !!!


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## shaygetz (Sep 23, 2007)

Pfunmo said:


> It's not a firm line and there can be all kinds of different varieties that fit in between. Kind of like definitions of generations of people?


I was raised to believe that the divider between first and second generation would be their shape, with 1st gen going to streamlined Fs, Es, C-liners, SWs, ***, RSs and Erie builts. The utilitarian looks of Geeps, U boats and C class Alcos marked the second generation with the boxy, cost effective car bodies being the new innovation for Class 1 and 2 roads. 

Always a great topic to bandy about...:laugh::thumbsup:


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## Pfunmo (Feb 21, 2013)

That's where I begin to find all kinds of different definitions depending on how they are looking at the machine. The guy that designed it and has a "better" idea will want his to be a new generation. The guy that drives it may think it is the same of thing if the mechanicals are the same. The guy selling it as a flashy new engine to pull a crack passenger run may have a different spin. Then when it all gets down to what the different media sorts tell us as hobby folks I just never really got into trying to sort out whose story to go along with. Hard enough for me to try to keep the history straight without trying to fit it into neat little categories! 
Can you tell I've been out shopping for the "BEST" laptop? That normally has a definite effect on my mind!


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## cv_acr (Oct 28, 2011)

shaygetz said:


> I was raised to believe that the divider between first and second generation would be their shape, with 1st gen going to streamlined Fs, Es, C-liners, SWs, ***, RSs and Erie builts. The utilitarian looks of Geeps, U boats and C class Alcos marked the second generation with the boxy, cost effective car bodies being the new innovation for Class 1 and 2 roads.
> 
> Always a great topic to bandy about...:laugh::thumbsup:


F7s and GP7s both have the same 1500hp engine in them, and GP7 and GP9 road switchers are definitely both first-gen units. You see a massive redesign between those units and later second-gen EMD road switchers though, with the later units having the single large radiator at the rear and the "clean air room" with the air intakes and filters at the front behind the cab.


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