GE Road Switcher Spotting Features

I am compiling a list of spotting features of various manufacturers for a novice railfan. EMD's, Fairbanks Morse and Alcos were pretty easy. But I am kind of stumped when it comes to GE's. I know one when I see one. But ask me how I know and I cannot come up with anything better than "flat nose, taperred cab roof."

I figured you guys could help me out.

Spotter's marks for telling that it IS a GE, or for telling WHICH GE model it is?
For the first: single stack in center of hood, at rear of engine compartment. Of course, this applies to Alcos, too, but it rules out FM and EMD types. Radiators at rear (rules out early EMD GP and SD units that split the radiator into forward and rear halves), fan under radiator (so fan not visible from overhead: basically rules out most EMD). Problem is how to distinguish GE from Alco. Fuel tank on GE prior to Dash-9 had a vertical flat side down an appreciable potion of the total depth, then angled in below that. (Dash-9 and AC have two angles, so there is a narrower vertical above a slightly angled in above a more sharply angled in part: three "slats" in the side.) This radiator design is very recognizable and distinctive. Only exception I know is the B32-8WH (Amtrak only) which has a small curve-sided fuel tank that looks much more like an EMD tank.

Thanks Allen,

Generally, it is the Alco Century and the early GE's which have most novice spotters stumped. I'd always been able to tell the difference by the cab roof -- Alco's round, GE's tapered -- but it wasn't until I tried to make the list that I realized this.

Something to watch out for with GE's, was that GE often changed models (i.e., the internal mechanical contents) without changing the carbody of the locomotive too much and then change the carbody midway through the production of a particular model. I recall that the U-series was notorious for this, that like (only for example) a late U28B and early U30B would have the same external appearance, while an early and late U28B might look very different.

Camelback--
Yes, it's the Alcos that are hardest to state the difference between and the GE units! Maybe not surprisingly, given their technological similarities (turbocharged engines of similar dimensions, etc). Maybe there was even a similar design philosophy, running back to the days of the Alco-GE consortium: both, for example, put radiators at the end of the hood with the fans-- fans mechanically powered from a crankshaft extension on Alcos and pre-Dash-8 GEs, instead of fans with separate electric motors-- under rather than over the grids.
I'd point to the hood ends as well as the cab roof. GE (except for things like the UD18B and the first two U25B demos ("XP24") have rounded edges. 251-engined Alcos, even when they don't have notches, have at least one pair of sides (typically the end and the top) meeting at a sharp angle. (Of course this makes GE's soud like RS2/RS3 era Alcos! If your guide is to be used outside the U.S., you'll need a warning footnote about the Queensland (Australia) units from the early 1950s: they were a GE export, with an ancestor of GE's FDL engine, but have a carbody design startlingly reminiscent of an RS-3!)
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One thing that helps, bu that you need practice recognizing: handrails on GEs are made from a larger diameter pipe than those on EMDs and Alcos. But you're right, maybe the best thing to do if you have just one drawing is to show the cross section of the GE (U25 thrugh Dash-7) cab roof.

How about they are very dirty and the engineer looks frustrated.