Ironically, I was asking myself the same Q last weekend.
(And I'm sure I'm not the first. Pondering the question what to do with the Atlas 50' might be a rite of passage for all Nskulls)
Here's my unfinished notes ....
Several board threads suggested elsewhere that the ATLAS 50' flatcar was loosely based on ACF USRA flat and is as much a modeling compromise by Roco (original mold maker) to represent various types, but not anything specific. They have had at least two different configurations - 50' w/ a 40' trailer, and 50' w/ 2 24' trailers. The decking of both is similar, but has different hole patterns to attach the respective trailers. The trucks on the ones I have all seem to be Atlas's common 40 ton Bettendorf truck with friction bearing journals. (Friction bearings were banned from interchange in '53. So think late steam to transition era.)
Mark's pic:
http://www.spookshow.net/freight/atlasrocopiggy.html As I happened to have this exact car (Limited edition! Original Rapido couplers! Austria Import! Only 30 million made! Mint Acme trailers! [dynamite and rocket rollerskates not included] here are my measurements (N Scale):
Length over sills: 95 mm (49' 10.5")
Distance between trucks: 73 mm (38' 3.8")
height of sill at center (underside of deck to bottom of fishbelly sill): 5 mm (2' 7.5")
height of sill at bolster: 3 mm (1' 6.9")
length of fishbelly sill bottom: 34mm (17' 10.2')
length of horizontal section of sill bottom above trucks: 17mm (8' 11.1")
width over sills: 18 mm (9' 5.4")
Spookshow sez it looks like a 42' USRA flat. According to Lucas, "100 years of railroad cars",pg 68 is a diagram of the 55-ton USRA steel underframe car of 1919. (12 pockets, 42' 1.5" over end sills)
Like the model, the two center sills are a bit deeper than the two side sills, but unlike the model (where the section of the outer sill at the trucks stays horizontal till the inner axle) the prototype is horizontal to a point midway between the bolster beam and the inner axle, actually obscuring a bit of the inboard wheelset.
Your railroad - you be the judge. For me, meh. A stand in at best. And would take a considerable effort to make it true. Start by removal of 7mm from the center gets you the 12 pockets evenly spaced, a length over the sills of 46' 2.3" and fishbelly about 10mm long (still about 1' 3" too long). I guess you could then trim the ends, but then you are moving bolster, scraping and reapplying pockets and rivets.
But with so may flat cars out there, there HAS to be something closer, right?
Digging a bit more, I found what I think is a semi-bingo on the 13 pocket stake 50' F30d of the PRR (you'd think the word "Pennsylvania" painted in white on the side should have been a hint!)
http://prr.railfan.net/freight/PRRdiagrams.html?diag=F30d.gif&fr=clhttp://pennsyrr.com/index.php/data/86-modeling/200-alan-curtis-models-f30a-and-f30d-flat-cars"Built in 1951 and were of a cast frame design. There were 250 cars in the class, of which 115 were converted for TOFC service, later known as TrucTrain, in 1954."
Other than the small one with the diagram, I can't find any pics on line but apparently there are two in Sweetland's "PRR Color Guide to Freight and Passenger Equipment Volume 1." I'm kind of interested to confirm the rivets, as these cast sills might not have required such.
The model's fishbelly is still a tad long and wide, and it would be GREATLY improved by a new deck kept between the pockets and a z gauge body couplers with repaired ends. Maybe a rivet scrape and adding some styrene to the bottom edge of the fishbelly sill to give a cast I beam cross section?
But I model SoCal in the late twenties. This car isn't going to help me.
So turning to Occhiello's AT&SF live list, I found 50' Ft-K (ACF 1915) which would be a somewhat useful car to me (although AT&SF reports just 24 of them in their 1927 roster)
From the Folio 211/4 diagram, it seems that this car was close.
http://atsfrr.net/resources/zebrowski/folio/ft-pdf/ft-k.pdf The drawing suggests no pocket stakes at all. The car was only 1.6" longer at the sills. Width 7.5" narrower at the sills. The fishbelly bottom was 3.5" narrower from under the deck. The distance between the truck bolster centers of the car is about 16" greater than the model. The biggest diff is the fishbelly bottom length of the prototype is a full 3"10" shorter likely from a less steep angle of the belly.
Anyone have a picture of an as built 50' Ft-K? R# Series 92500-92524 Need to confirm a few things such as did it have a true fishbelly sidesill. It seem many of the AT&SF flats had 6 sills, of which the 4 inners where fishbelly steel and the an outside nonfishbelly wood side sill. But otherwise, replace with low profile Andrews trucks, z coupler and some styrene for the ends, scrape off pockets and replace Archer rivet as desired. add a wood deck. Decals, paint and heavy weathering, and she's fit for duty.
Another promising AT&SF flat might be 50' fish belly Ft-L (PSCM 1924). Hendrickson also did a an article on making the Ft-L from the Athern 50 in HO (5, Santa Fe Modeler 1Q88,pg.23-27) which I've yet to locate.
I'm also considering a splice. Wish I could take credit for this general concept, but no - far from it. Credit goes again to Hendrickson's HO work "Kit Bashing FT-G and FT-V Class Flat Cars--From Athearn 40 and 50 Flat Car Kits"
But with the Atlas 50, I'm exploring two other AT&SF cars - making an off center cut of two 50's to attempt to create AT&SF as modified 53' 15 stake pocket Ft-L (PSCM) and a AT&SF 44' Ft-M (ACF 1924).
And that is about where my research hit a wall.
I don't yet have the "as built" diagrams or images of either. Just later diagrams as modified (ex '57 FT-M as a TOFC with 12 pocket). I've one (
http://www.sunshinekits.com/sunimages/sun66.pdf) states the Ft-L were actually built as 50' fishbellies but extended to 53'6" around 1946.
Another Santa Fe car that won't fit my era, but actually ran until the 90's was the Class Ga-108 52' steel gondola (GATCo '58). Add about a scale 1'4" to each end, and move out the trucks, add gon sides of v thin flat sheet styrne with relief holes for the stake pockets, then add stakes and blow out the sides a bit near the floor. Add ladder and lip, and it would look close enough for me. My 211/4 diagram of this car shows it as a 15 stake pocket, but here in San Diego is one of the real things... and it has the magic # 13. (
https://www.psrm.org/trains/freight/atsf-72312/)
Also I' looking at Espee flats (the F-50-2 sounds promising. Apparently such was a 50' 11 or 12 pocket, fishbelly flat, but I'm lacking on hand resources to confirm such.
