On Jan 28, 2023, at 9:00 PM, Dave Wetterstroem <framemakers@...> wrote:

This week I am working on flat cars for my clinic on curating your C&O freight car fleet at the upcoming C&O Modelers Weekend in Logan WV. 
The focus of my presentation is 1952. At this time, the C&O didn't have much of a flat car fleet with only 544 cars (not counting former PM cars). 

The car I am currently wondering about is the 81000-81249 series that were built by Greenville Steel Car Co in 1952. These were 70 ton, 53'6" cars with 15 side pockets. The P2K 50 ton AAR flat looks very close to my eye. The car diagrams from the 80625-80724 AAR 50 ton flats from 1944 also look nearly identical to the ones for the 81000 series. 

What would the visible differences be between the the 50 ton AAR and these 70 ton cars? 

Dave,

Without getting too much into the weeds, the short answer is that Greenville Steel Co. (GSC) built four series of 70-ton flat cars in 1951-1953 including C&O 81000-81249 built to the same basic geometry as the 50-ton AAR flat cars but with three primary exceptions:

1. These GSC 70-ton flat cars came with 4 crossbearers of unequal spacing vs. three crossbearers of equal spacing for 50-ton AAR flat cars. Both designs have 21’-5 1/2” spacing to outermost crossbearers. Whereas the innermost pair of crossbearers for these GSC cars had a spacing of 7’-6 1/2” (3’-9 1/4” towards both ends from the car’s longitudinal center line).

2. Due to the additional crossbearer, the GSC cars had one less crosstie (7) vs. eight crossties for the 50-ton AAR flat cars. This changed the respective locations of the crossties primarily between the 4 crossbearers but also minor spacing differences between the bolsters and outermost crossbearers.

3. Larger sizes and thickness of many built-up structural components comprised of rolled steel angles, webs, and cover plates as applicable to the center sills, side sills, crossbearers, and crossties. Whereas the bolsters were comparatively much the same as were the end sills.

Following are the 4 Greenville Steel Co. Office Orders (O.O.).

WM 2601-2640, GSC O.O. 562, 40 cars built 7-51 (railroad class F-8)

NKP 3100-3249, GSC O.O. 567, 150 cars built 8-51

C&O 81000-81249, GSC O.O. 579, 250 cars built 3-52

WM 2641-2710, GSC O.O. 584, 70 cars built 2-53 (railroad class F-9)

Also, the NKP Brewster shops built 100 cars 3250-3349 in 4-57 to the same specs.

The wood decking for these Greenville 70-ton cars were the same as 50-ton AAR flat cars with continuous wood from end sill to end sill. The C&O & NKP cars used 2 3/8” x 7 3/4” x 10’-6” deck boards vs. 2 3/4” x 7 3/4” x 10’-6” for the WM cars.

Other differences of these four Greenville orders are various customer options/choices to include the shape of the stake pockets, push-pole pockets (NKP 3100-3249 lacked push-pole pockets), locations of roping staples, and specialties from suppliers for the hand brakes, defect card holders, and trucks. 

A 4th dimensional difference is of course 70-ton trucks with 5’-8” axle centers vs. 5’-6” for the 50-ton AAR flat cars. 

My hope is this helps to answer your question. If you want to delve more into the weeds, please contact me off list at hawk0621@.... 

Regards,

Ed Hawkins