The rib-sided cars preceded the Hudson by two years. Read Scribbins' text. The new cars were introduced in 1936 and 1937 to create a more lightweight train behind the Atlantics. The F7 Hudsons picked styling cues from those cars, not the other way around, in 1938.
I'm not sure what you mean the post has nothing to do with Lionel, since I was responding to a post that cited the accuracy of Lionel's Atlantic and matching 18-inch cars, which were in fact a prototypically correct set.
Jim, have to take one more shot at this. The smooth side cars were made for the Atlantic and the Rib sided cars for the Hudson.
The rib sided cars made by LIONEL were correct for the Hudson and not the Atlantic.
I never really intended to comment on your Lionel post
I'll try one more time to try to undo your erroneous stubbornness.
From "A Hiawatha Story" by Jim Scribbins, beginning with the chapter marked "Ribbed Cars and 4-6-4's" on page 40 of the original Kalmbach book (copyright 1970):
"New equipment for the Hiawatha was exhibited at Chicago, Milwaukee, scheduled intermediate stops, and the Twin Cities October 5-10, 1936, and entered regular service on the 11th -- a totally new train (except for the motive power) after only 16 months of service. Opportunely, the number plates on the A's were such that the Two-Spot could be used advantageously to illustrate material pertaining to the consist of the second Hi.
"The Hiawatha of 1937 incorporated several notable improvements. Cor-Ten steel and aluminum alloys were employed to further reduce weight so that the cars weighed 41 to 43 percent less than the standard equipment, and the new nine-car train weighed but 27 tons more than the seven-car train of 1935 ...
"For the first time the trademark of fluting, or ribbing, appeared on the car sides above and below the windows, which were squared off in contrast to the convex-style windows of the first train."
On pages 46-47, the cars are pictured in a photo sequence from October 18, 1940, being pulled by Hiawatha Class A Atlantic no. 3.
From page 43:
"In February 1938, CMStP&P announced plans to acquire 55 passenger cars and 6 new locomotive's (by this time No. 4, which turned out to be the last of the Atlantics, had been strutting its stuff for approximately 10 months), primarily for Hiawatha Service.
"Meanwhile, back at the shops and at Schenectady, the assembly lines had been busy. For three days the third set of equipment, accompanied by a brand-new F-7 Hudson, was exhibited in Chicago, Milwaukee and the Twin Cities, with a brief showing at intermediate stops, and on September 19, 1938, the Hiawatha of 1939 entered service. The 1936 replacement of the first train had been unprecedented in rail history; this was even more astounding."
So, in summary: the Atlantics were introduced in May 1935 pulling the original smooth side cars, which were replaced beginning in 1936 by the rid sided cars. The Hudsons were not even designed at that point, but were introduced in 1938. The Atlantics continued to be used in Hiawatha service for a time as well as the Hudsons.
Now show me some authoritative text that says otherwise.